Abstract Translational in vivo models are needed to expedite the discovery of new treatments for lung cancer. One such approach is the use of humanized mouse models that enable immunotherapies targeting human immune cells to be evaluated for efficacy and tolerability. We developed an orthotopic lung carcinoma model in humanized mice (HuCD34 NCG), utilizing serial bioluminescence imaging to evaluate the activity of paclitaxel and pembrolizumab as single and combination agents. Paclitaxel, which disrupts microtuble function, and pembrolizumab, a PD-1-targeting immunotherapy, are both approved for the treatment of certain types of lung cancer. Paclitaxel kills cancer cells directly, and may also promote anti-tumor responses through enhanced presentation of tumor antigens and activation of T cells. Immunodeficient NCG mice were humanized with cord blood-derived hCD34+ stem cells from 3 donors. High levels of human cell engraftment, with expected frequencies of hCD45+ cells and other immune subsets, was observed by 14 weeks post-injection. Luciferase expressing A549 cells were implanted orthotopically into the pulmonary space of the left lobe of the lung, and animals were subsequently flux sorted into treatment groups. Tumor burden, measured by luciferase expression, increased progressively in untreated animals, and moribundity was often associated with clinical indications of respiratory distress. Treatment with paclitaxel significantly decreased the tumor burden and extended survival. In contrast, pembrolizumab did not control tumor growth or extend survival. There was no synergistic effect with the combination therapy, in fact, the addition of pembrolizumab was associated with a modest increase in tumor burden and disease progression. Comparative analysis of immune cell composition, function and persistence in lung and other tissues provided insights into the distinct pharmacodynamic responses associated with the different treatment regimens. This model establishes a robust in vivo platform to identify novel therapies for the treatment of lung cancer. Citation Format: Anya Avrutskaya, Elizabeth Rainbolt, Bincy John, Cara Clouse, Murray Stackhouse, Christopher Currie, Sydney Scatigno, Steven Bronson, Jenny Rowe, Chassidy Hall, David P. Harris. Development of an orthotopic A549 lung carcinoma model in CD34+ humanized NCG mice and response to treatment with paclitaxel and pembrolizumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4186.

The cancer immunotherapy field has seen an increasing demand for identifying and characterizing pre-clinical models to evaluate the efficacy of the checkpoint inhibitors such as, ipilimumab and pembrolizumab. PBMC- or CD34-humanized mouse models are invaluable tools to assess effector functions of human T-cells to immune check point inhibitors (ICI). However, these models offer limited understanding of the overall potential therapeutic activity as they lack a complete repertoire of human immune cells required to elicit a full immune response. Thus, the development of multigenic humanized knock-in models provide a unique approach to evaluate the efficacy of ICI specific for human cancer targets in a fully immunocompetent organism. Here we describe the response of the EMT-6 murine breast cancer tumor model to ipilimumab and pembrolizumab in a novel hPDCD1/hCTLA4-KI double knock-in humanized BALB/c mouse model. EMT-6 tumors were implanted subcutaneously in the flank of hPDCD1/hCTLA4-KI mice. Three days post-implant we initiated treatment with ipilimumab or pembrolizumab alone and in combination. We observed significant ipilimumab anti-tumor activity, whereas pembrolizumab did not show efficacy despite effective T-cell PD-1 blockade. Unexpectedly, sudden respiratory distress occurred in animals receiving the 4th dose of combination therapy and the treatment was discontinued. To assess the immune phenotypic profiles in response to ipilimumab and/or pembrolizumab therapies, we performed multi-parameter flow cytometry analysis of peripheral blood, spleens and tumors. Additionally, we performed histopathological evaluation of lung tissues to assess potential neutrophil infiltration-mediated anaphylaxis in the mice treated with the combination treatment. The preliminary results highlight the value of the hPDCD1/hCTLA4-KI double knock-in humanized Balb/c model as a tool to evaluate human-specific immune-checkpoint based modalities. These models represent some of the difficulties faced in treating refractory tumors as well as reproducing some of the adverse effects seen in the clinic. Citation Format: Murray Stackhouse, Mariah Kuta, Joseph Kolb, Sydney Scatigno, Amber Blackwell, Chassidy Hall, Christopher Dowdy, Payel Sil, Diana Gietl, Steve Festin, Paula L. Miliani De Marval. Utilization of a novel double knock-in humanized mouse model to evaluate the efficacy of ipilimumab and pembrolizumab against EMT-6 mammary carcinoma tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2583.

Abstract The human checkpoint genes PD-1 and PD-L1 have been the target of extensive research for the treatment of human malignancies. Checkpoint inhibitor therapy has shown great promise in the clinic. Animal models that can use the human clinical antibodies will be beneficial for evaluating new therapies. A novel transgenic mouse model was developed that expresses the human PD-1 and PD-L1 in place of the murine genes. Additionally, a murine MC38 colon tumor cell line was modified to express human PD-L1. We evaluated the efficacy of human check point antibodies nivolumab, pembrolizumab, and atezolizumab in the transgenic animal model with modified MC38 colon cancer cells. Five hundred thousand transgenic MC38 cells were implanted in the C57BL/6 PD-1/PD-L1 knock in mice and allowed to grow for three days. The tumor-implanted mice were treated with nivolumab and pembrolizumab at 100 μg per animal and atezolizumab at 1 mg per animal on Days 3, 7, 10, and 14. Treatment with nivolumab and pembrolizumab caused tumor regression by Day 17. Growth inhibition was 84%, 58%, and 94% on Day 17 for nivolumab, atezolizumab, and pembrolizumab, respectively, compared to the control animals. There was no significant body weight loss and no signs of toxicity in any of the treated animals. We have shown that both PD-1 and PD-L1 inhibitors are effective in treating genetically modified MC38 colon tumors in transgenic mice. Further research will involve combining each of the checkpoint antibodies with various chemotherapeutic agents. Citation Format: Murray Stackhouse, Ted Green, Jay Liu, Charlotte Hammond, LaJuana Durbin, Anna Chen, Mike Koratich. Efficacy of nivolumab, pembrolizumab, and atezolizumab against MC38 colon cancer expressing human PD-1 in transgenic C57BL/6 mice expressing human PD-1 and PD-L1 checkpoint genes [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B81.

The human checkpoint targets PD-1 and PDL-1 continue to demonstrate great promise in the clinic. With much of the current focus turning toward combination regiments, an animal model using the human clinical antibodies will be beneficial for evaluating new combination strategies. Here we continue characterization of a C57BL/6 transgenic mouse model expressing both the human PD-1 and PD-L1 combined with a modified murine MC38 colon tumor cell line expressing human PD-L1. Both PD-1 and PD-L1 expression of the transgenic mice were verified in ex vivo stimulated splenocytes by flow cytometry analysis. Expression of PD-L1 on the genetically modified MC38 cells was also demonstrated by flow cytometry. For in vivo efficacy evaluation, tumor-implanted mice were treated with the clinical agents nivolumab and pembrolizumab at 100 µg and atezolizumab at 1 mg on Days 3, 7, 10, and 14 post implant. Treatment with nivolumab and pembrolizumab initiated tumor regression by Day 17. Complete tumor regressions were seen at Day 28 in nivolumab, 62.5% complete regression, and pembrolizumab, 71.4% complete regression. Growth inhibition was 83.9%, 69.7%, and 95.0% on Day 28 for nivolumab, atezolizumab, and pembrolizumab, respectively, compared to the control animals. There was no significant body weight loss and no signs of toxicity in any of the treated animals. To compare the human anti-PD-1 and PD-L1 clinical agent specificity, the non-transgenic parent C57BL/6 mouse strain was implanted with the unmodified MC38 colon tumor cells. Treatment with pembrolizumab and atezolizumab was conducted as with the transgenic animals. Through 28 days no growth inhibition, tumor size 105.9% of control, was seen in the pembrolizumab treated group, demonstrating lack of cross reactivity of the human therapeutic in the standard mouse model. Atezolizumab did demonstrate a 56.9% growth inhibition compared to controls and is consistent with the known cross reactivity of atezolizumab between human and mouse. We have shown a genetically modified MC38 colon tumor expressing human PD-L1 in transgenic mice expressing both human PD-1 and PD-L1 to be a suitable model for checkpoint inhibitor evaluation of the human form of the particular checkpoint therapeutic. Further research will involve combining each of the checkpoint antibodies with various chemotherapeutic agents. Citation Format: Michael Koratich, Ted Green, Jie Liu, Charlotte Hammond, LaJuana Durbin, Jerry Zhou, Anna Chen, Murray Stackhouse. Characterization of a MC38 mouse syngeneic tumor model expressing human PD-L1 in the transgenic C57BL/6 mouse system expressing human PD-1 and PD-L1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1504.

5-aza-2′,2′-difluorodeoxycytidine (NUC013) has been shown to be significantly safer and more effective than decitabine in xenograft models of human leukemia and colon cancer. However, it suffers from a similar short half-life as other DNA methyltransferase inhibitors with a 5-azacytosine base, which is problematic for nucleosides that primarily target tumor cells in S phase. Because of the relative instability of 5-azanucleosides, a prodrug approach was developed to improve the pharmacology of NUC013. NUC013 was conjugated with trimethylsilanol (TMS) at the 3′ and 5′ position of the sugar, rendering the molecule hydrophobic and producing 3′,5′-di-trimethylsilyl-2′,2′-difluoro-5-azadeoxycytidine (NUC041). NUC041 was designed to be formulated in a hydrophobic vehicle, protecting it from deamination and hydrolysis. In contact with blood, the TMS moieties are readily hydrolyzed to release NUC013. The half-life of NUC013 administered intravenously in mice is 20.1 min, while that of NUC013 derived from intramuscular NUC041 formulated in a pegylated-phospholipid depot is 3.4 h. In a NCI-H460 xenograft of non-small cell lung cancer, NUC013 was shown to significantly inhibit tumor growth and improve survival. Treatment with NUC041 also led to significant tumor growth inhibition. However, NUC041-treated mice had significantly more tumors ulcerate than either NUC013 treated mice or saline control mice, and such ulceration occurred at significantly lower tumor volumes. In these nude mice, tumor regression was likely mediated by the derepression of the tumor suppressor gene p53 and resultant activation of natural killer (NK) cells.

Vitamin E phosphate (VEP) nucleoside prodrugs are designed to bypass two mechanisms of tumor resistance to therapeutic nucleosides: nucleoside transport and kinase downregulation. Certain isoforms of vitamin E (VE) have shown activity against solid and hematologic tumors and result in chemosensitization. Because gemcitabine is one of the most common chemotherapeutics for the treatment of cancer, it was used to demonstrate the constructs utility. Four different VE isoforms were conjugated with gemcitabine at the 5′ position. Two of these were δ-tocopherol-monophosphate (MP) gemcitabine (NUC050) and δ-tocotrienol-MP gemcitabine (NUC052). NUC050 was shown to be able to deliver gemcitabine-MP intracellularly by a nucleoside transport independent mechanism. Its half-life administered IV in mice was 3.9 h. In a mouse xenograft model of non-small cell lung cancer (NSCLC) NCI-H460, NUC050 at a dose of 40 mg/kg IV qwk × 4 resulted in significant inhibition to tumor growth on days 11–31 (p < 0.05) compared to saline control (SC). Median survival was 33 days (NUC050) vs. 25.5 days (SC) ((hazard ratio) HR = 0.24, p = 0.017). Further, NUC050 significantly inhibited tumor growth compared to historic data with gemcitabine at 135 mg/kg IV q5d × 3 on days 14–41 (p < 0.05). NUC052 was administered at a dose of 40 mg/kg IV qwk × 2 followed by 50 mg/kg qwk × 2. NUC052 resulted in inhibition to tumor growth on days 14–27 (p < 0.05) and median survival was 34 days (HR = 0.27, p = 0.033). NUC050 and NUC052 have been shown to be safe and effective in a mouse xenograft of NSCLC.

In this letter we report first nonpeptide inhibitors of hepatocyte growth factor (HGF) activation. These compounds inhibit the three proteases (matriptase, hepsin, and HGF activator) required for HGF maturation. We show that 6, 8a, 8b, and 8d block activation of fibroblast-derived pro-HGF, thus preventing fibroblast-induced scattering of DU145 prostate cancer cells. Compound 6 (SRI 31215) is very soluble (91 μM) and has excellent microsome stability (human t 1/2 = 162 min; mouse t 1/2 = 296 min). In mouse 6 has an in vivo t 1/2 = 5.8 h following IV administration. The high solubility of 6 and IV t 1/2 make this compound a suitable prototype "triplex inhibitor" for the study of the inhibition of HGF activation in vivo.

Abstract The procedure to identify and develop an anti-cancer drug first involves testing drug candidates in cell lines followed by human tumor xenograft models, usually selected based upon the histotype of the cell lines in which the drug showed optimal activity. Many drugs fail at this stage, as activity in cell lines does not often correlate with activity in xenograft models. This is not surprising, as we have previously shown that gene expression in xenograft models does not necessarily correlate with the cell line from which it was derived. In an attempt to improve the success rate of drugs tested in xenograft models, we have developed a fast and cost effective 12-panel human tumor cell line assay that represents the genetic diversity of all our xenograft models and several different cancer histotypes. Affymetrix genomic analysis was performed on 100 human tumor xenograft and cell line models. The genomic profiles obtained underwent Unsupervised Hierarchical Cluster Analysis to group models with similar genetic profiles. This analysis resulted in 12 distinct clusters; a representative cell line was chosen from each cluster. Stocks of each representative cell line were frozen and tested to ensure exponential growth immediately upon thawing, resulting in no waiting time for drug testing. It follows that if a candidate drug shows activity in one or more of these representative cell lines, other cell lines and/or xenograft models in the same cluster can also be tested. As the cell lines and xenograft models within the same cluster will have a similar genetic profile, the chances of success should thus be increased. To test the effectiveness of this approach, we used our database to further develop an internal compound. SRI-20900 had been tested previously in the CCRF-CEM and CAKI-1 xenograft models. The compound showed no activity in CCRF-CEM cells, but excellent activity in CAKI-1 cells. These models were in completely different clusters. So, based on these data, we tested the compound in the SKOV-3 and IGROV-1 xenograft models, as these clustered closely to the CAKI-1 model. The compound showed excellent activity in both SKOV-3 and IGROV-1 models. Although these data provide proof of principle, further work needs to be done by testing targeted compounds in the 12-cell line panel, followed by testing in xenograft models within the same cluster as the cell lines that show optimal activity. In addition, it would follow that a xenograft model within the same cluster as an inactive cell line should also be tested. We hope to start these studies early in 2014. Citation Format: Michael J. Roberts, Tommie A. Gamble, Richard D. May, Murray Stackhouse, Kristy L. Berry, Andrew D. Penman, Robert J. Rooney, Yulia Maxuitenko, Michael S. Koratich. A quick and cost effective 12-cell line panel assay to predict drug activity in human tumor xenograft models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3730. doi:10.1158/1538-7445.AM2014-3730

Traditionally, drug development has relied upon testing cancer drug candidates in cell lines. Active drugs are then tested in human tumor xenograft models, usually selected based upon the cell lines in which the drug showed activity. The majority of drugs fail at this stage as they do not show activity in the xenograft models chosen. We performed Affymetrix genomic analysis on 42 human tumor xenograft models and the original cell lines from which they were established. The genomic profiles obtained underwent Unsupervised Hierarchical Cluster Analysis to ascertain which cell lines and xenograft models had similar genomic profiles and which did not. The analysis showed that only 24 of 42 human tumor xenograft models clustered side-by-side with the cell line from which they were established. All 6 human leukemia/lymphoma xenograft models clustered very well with the cell lines from which they were established, and they clustered perfectly according to histological class. Five out of six human colon tumor xenograft models clustered well with the cell lines from which they were established and according to histotype. Of the 18 xenograft/cell line pairs that did not cluster side-by-side, 10 pairs remained in the same general cluster, whereas the partners of 8 other pairs were dispersed across different major clusters. Ovarian, breast, melanoma, and pancreatic human tumor xenograft models did not cluster according to histotype. Our data may explain why some drugs that show in vitro activity in some cell lines are not active in other cell lines of the same histological type, and also why some drugs that show activity in vitro then fail in xenograft models. In our laboratory, the PANC-1 cell line is very often chosen as a model of pancreatic cancer. A drug showing activity in the PANC-1 cell line would next be tested in other in vitro models of pancreatic cancer (e.g., MIA PaCa-2, CFPAC-1, and BxPC-3). However, none of these other pancreatic models have a similar genetic profile to PANC-1. Based upon our data, the cell line showing most similarity to the PANC-1 cell line is the breast cancer cell line MDA-MB-231. It is our suggestion that a drug showing activity in the PANC-1 cell line should be tested in other cell lines showing similar genetic profiles, not in cell lines based on histotype. Another example from our analysis is the LOX-IMV1 melanoma cell line. Not only does this cell line not cluster with its corresponding LOX-IMV1 xenograft model, it clusters most closely with the NCI/ADR-RES ovarian cell line. In summary, the genomic profiles of approximately 57% of the tumor xenograft models analyzed closely associate with the cell line from which they were established. Some of the tumor xenograft models show very little similarity to the cell lines from which they were established. Additionally, many of the models (both xenografts and cell lines), do not cluster according to their tissue of origin. Citation Format: Michael J. Roberts, Michael S. Koratich, Murray Stackhouse, Richard D. May, Andrew D. Penman, Tommie A. Gamble, Kristy L. Berry, Joseph F. Murphy, Robert J. Rooney, Yulia Y. Maxuitenko. Tumor target vs. tissue of tumor origin: cluster analysis of genomic profile of 42 human tumor in vitro and in vivo models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2778. doi:10.1158/1538-7445.AM2013-2778

PURPOSE:Activation of the DNA damage responsive protein kinase ATM is a critical step for cellular survival in response to ionizing irradiation (IR). Direct targets of ATM regulating radiosensitivity remain to be fully investigated. We have recently reported that ATM phosphorylates the transcriptional repressor Snail on Serine 100. We aimed to further study the functional significance of ATM-mediated Snail phosphorylation in response to IR.MATERIAL AND METHODS:We transfected vector-only, wild-type, the Serine 100 to alanine (S100A) or to glutamic acid (S100E) substitution of Snail into various cell lines. We assessed colony formation, γ-H2AX focus formation and the invasion index in the cells treated with or without IR.RESULTS:We found that over-expression of the S100A mutant Snail in HeLa cells significantly increased radiosensitivity. Meanwhile the expression of S100E, a phospho-mimicking mutation, resulted in enhanced radio-resistance. Interestingly, S100E could rescue the radiosensitive phenotype in ATM-deficient cells. We also found that expression of S100E increased γ-H2AX focus formation and compromised inhibition of invasion in response to IR independent of cell survival.CONCLUSION:ATM-mediated Snail Serine 100 phosphorylation in response to IR plays an important part in the regulation of radiosensitivity.

Tumor growth is not determined solely by the tumor cells but is governed by interactions between tumor cells and host stromal cells, including endothelial cell activation and fibroblastic stroma response. Tumor stroma profoundly influences many steps of tumor progression. In many human cancers, such as breast, prostate, and colon, the stroma comprises the majority of the tumor mass, as a hallmark of the clinical feature called desmoplasia. Numerous studies have showed that tumor-stromal cell interactions play crucial roles in supporting cancer progression and in promoting anticancer drug resistance by alternating gene expression profiles in both tumor and stromal cells through network tumor-stromal interactions in the tumor microenvironments. It has been challenging to obtain separate gene profiles for tumor and stroma with human tumor samples as both tumor and stromal cells share the same genome. In xenograft mouse tumor models, human tumor cells are supported by mouse host stromal microenvironment. Therefore, effects of tumor stromal integrations on gene expression can be profiled separately by taking advantage of this heterogeneous genetic makeup. To understand the underlying biological process of stroma in cancer and select relevant in vitro and in vivo model systems for various targeted anticancer drug discovery and development projects, we selected a panel of 30 commonly used xenograft tumor mouse models that are derived from human tumor cell lines of various cancer histotypes and conducted analyses of differential gene expression in both human cancer cells and mouse host stromal cells before and after their interactions in vivo by using quantitative PCR with mouse and human specific primers. Growing the human tumors as a continuous in vivo passage subcutaneously in immunodeficient mice permits stroma infiltration over a long time. We have examined a number of anticancer target genes involved in different signaling pathways, such as tumor angiogenesis, apoptosis and survival (Akt/mTOR signaling pathway). Our study results have demonstrated that tumor stromal interactions significantly regulate expression levels of various genes important in tumor progression and development of resistance to treatment in both tumor and stromal cells. Tumor animal models play a critical role in translating the bench science to the bedside medical care of cancer patients. Decisions for moving new anticancer agents into costly clinical investigations are mostly based on the preclinical results using xenograft mouse models. The results of this gene profiling approach could provide tools for studying tumor microenvironment and tumor stromal interactions in vivo to advance anticancer drug development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3114. doi:10.1158/1538-7445.AM2011-3114

The NCI recently performed microarray expression analysis on its 60-panel of human tumor cell lines. This revealed important information, with some cell lines shown to be from a different tissue of origin than originally believed. Traditionally, potential anti-cancer agents have been evaluated in these in vitro models, and then moved into the corresponding in vivo xenograft model(s) based on the in vitro results. It has been shown that drugs which are effective in vitro are not necessarily effective in vivo and vice versa. Systematic microarray analysis of traditional xenograft models in conjunction with their in vitro counterparts has not been performed. The development of a human tumor xenograft in a mouse might be expected to lead to changes in gene expression, and this could account, in some instances, for the disconnect in results observed between in vitro and in vivo models. Our aim was to perform a genetic analysis against the entire human genome using 24 cell lines from 11 differing tissues of origin that were implanted into immune-deficient mice to establish a xenograft model for each. Once the tumors reached approximately 1 cm3 in size, the tumors were removed, cut into approx. 2-3 mm3 fragments, and an in vivo tumor passage was established. Microarray expression in fragments of those xenografted tumors was compared to microarray expression in the cell line from which they were developed. The total mRNA for each sample was split into 3 replicates, and analyzed against the entire human genome using standard Affx WT procedures. The results showed that over 60% (15 of 24) of the xenograft samples clustered with the cell line from which it was developed, whereas approximately 40% (9 of 24) did not, revealing that major changes in gene expression had occurred in 40% of these xenograft samples. Furthermore, when analyzed alone, these particular 24 cell line samples clustered according to their tissue of origin, whereas the tumor fragment samples did not appear to cluster. On the basis of these data we are currently performing the same analysis on an additional 25 tumor fragments and their corresponding matched cell lines to allow for a more accurate, in-depth cluster analysis. These data strongly suggest that although precedent exists to select in vitro models on the basis of their tissue of origin, no such precedent exists for in vivo models. In vivo models should be more carefully selected to ensure that the model chosen is still representative of the tissue to be tested. It follows that a drug candidate effective in a particular in vitro model might be expected to show activity in other in vitro lines from the same tissue of origin. However, a drug candidate effective in a particular in vivo model representative of a tissue of origin should not be expected to show efficacy in other in vivo models representing the same tissue type. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4418. doi:10.1158/1538-7445.AM2011-4418

The total mRNA for each sample of 51 human tumor cell lines representative of 16 different tissues of origin was split into 3 replicates, and analyzed against the entire human genome using standard Affx WT procedures. Approximately 50% of the samples (25 out of the 51 cell lines tested) exhibited low-level clustering related to their tissue of origin. The remaining 50% (26 out of the 51 cell lines tested) did not cluster with other samples of the same tissue of origin. These data reveal the importance of testing potential anticancer agents in multiple models representative of several different tumors of origin, as there is a 50% chance that the model chosen is not actually representative of the intended tissue of origin. This analysis also showed that the pancreatic cancer cell line CFPAC-1 did not cluster with any other cell line tested, revealing the unique genetic profile of this cell line. Interestingly, the reported lung cancer cell lines NCI-H69 and NCI-H82 clustered more closely with leukemic lines than with lung or any other solid tumor. This is particularly interesting as these lines are known to grow/behave more like a suspension culture than a monolayer. The NCI recently published its genetic analysis of their 60-panel, and they revealed that the MDA-MB-435 cell line, traditionally thought to be a breast cancer cell line, more closely resembled a melanoma line; hence, it was re-classified as a melanoma (likely a metastasized melanoma that was taken from the breast site). Our analysis reveals that another traditional breast cancer cell line, UISO-BCA-1, also clusters more closely with the melanomas (including the MDA-MB-435 cell line), suggesting that this cell line also may have been misclassified. Based on these data, we suggest that any potential anticancer agent showing activity in a particular cell line should be tested in other cell lines that cluster with the active line, and not merely in other lines supposedly representative of the same tissue of origin. Furthermore, in early stage testing, it would be more prudent to test several cell lines from different clusters, rather than several cell lines from different tissues of origin. It follows that by testing orphan drugs against several cell lines from each cluster, it would be possible to significantly narrow (and possibly identify), the likely drug target. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3943. doi:10.1158/1538-7445.AM2011-3943

1543 Imbalance in angiogenesis is involved in many pathological conditions, such as cancer, rheumatoid arthritis, and inflammation. Targeting angiogenesis has recently emerged as a proven therapeutic strategy for treatment of cancer and age-related macular degeneration. To understand the underlying biological signaling pathways of angiogenesis and to develop potential anti-angiogenic therapy, we have developed a system to discover small molecular probes that can selectively inhibit endothelial cell activation, and thereby block excessive angiogenesis. First, a high throughput screening (HTS) assay was developed for screening large libraries of chemical compounds against both primary human endothelia and fibroblasts to identify compounds with differential inhibitory activity against the endothelial cells versus fibroblasts. Second, HTS dose response-based EC50 values were determined to identify lead compounds with selectivity and potency against human endothelial activation. Third, a number of selected lead compounds were studied for their activities in endothelial cell tube-formation and migration, and to elucidate their mechanisms of action. Fourth, the selective compounds are being further studied in vivo by embryo CAM assay and mouse Matrigel plug assay. A number of compounds that exhibited specific inhibitory activities against human endothelial cells were identified from an 86,000 compound library screening. Analysis of structural clusters of the initial hits led to the identification of several chemical scaffolds as interesting leads. Structure-activity relationship (SAR) analyses and synthetic efforts on selected scaffolds for lead optimization are in progress. Our progress toward identification of specific anti-angiogenic agents will be presented.

421 We have previously shown that clofarabine radiosensitizes DLD-1 colon tumor xenografts (Proc. Amer. Assoc. Cancer Res. 48: 1196). The purpose of the current study was to determine whether other tumor xenograft histiotypes can be radiosensitized by clofarabine. Gemcitabine was used as a comparison for radiosensitization in all studies. We investigated six other xenograft models: NCI-H460 lung, SR475HN head and neck, SF-295 glioblastoma, DU-145 prostate, PANC-1 pancreatic, and HCT-116 colon. Mice were implanted with tumor fragments subcutaneously from an in vivo passage and the tumors were allowed to grow. Mice with tumors in the designated size range were selected for the studies. The NCI-H460 and SF-295 studies used 12 Gy total radiation delivered in four, 3 Gy fractions every three days combined with clofarabine injected by intraperitoneal (ip) injection daily for 10 days at a dosage of 30 mg/kg/injection. The remaining tumor models were given 20 Gy, in 2 Gy fractions daily for five days for two weeks combined with clofarabine injected ip daily for 12 days at a dosage of 30 mg/kg/injection. Clofarabine had no effect on the growth of SF-295 glioblastoma which was not enhanced by radiation. There was no difference between radiation alone and radiation combined with clofarabine in DU-145 prostate xenografts. The combined effect on NCI-H460 lung tumors appeared to be additive with T-C values (based on time to 3 tumor doublings) of 4.6, 9.4, and 16.9 days for clofarabine, radiation, and the combination, respectively. SR475HN head and neck tumors were radiosensitized by clofarabine with T-C values (based on 2 tumor doublings) of 16.7, 73.2, and >162 days for clofarabine, radiation, and the combination, respectively. PANC-1 pancreatic tumors were radiosensitized by clofarabine with T-C values (based on 2 tumor doublings) of 17.2, 1.7, and 62.9 days for clofarabine, radiation, and the combination, respectively. HCT-116 colon tumors were radiosensitized by clofarabine with T-C values (based on 3 tumor doublings) of 24.2, 29.3, and >78.9 days for clofarabine, radiation, and the combination, respectively. The radiosensitizing capacity of gemcitabine tracked with the clofarabine results. Three out of the six tumor models tested showed marked radiosensitization with clofarabine while another tumor model showed an additive effect. Two out of the six models tested showed no evidence of an interaction between clofarabine and radiation. Clofarabine has potential as a radiosensitizing cancer treatment.

1432 Larotaxel (RPR 109881A/XRP9881) is a taxoid, that is currently in development for breast cancer and other tumor types. Like docetaxel, it stabilizes microtubules, and has a broad spectrum of antitumor activity in taxane-sensitive tumors. In addition, it is active in vitro and in vivo against taxane-resistant tumors. In tumor-bearing mice, it was found to be active by the intravenous (iv) and oral route, and to cross the blood-brain barrier with activity against intracranial tumors (Proc AACR, 2004). The in vivo combinations of larotaxel with doxorubicin, cisplatin or vinorelbine were previously found synergistic (Proc AACR, 2005). We report here the preclinical in vitro and in vivo combination data of larotaxel with trastuzumab (herceptin®), using mammary UISO BCA-1, a human tumor model expressing Her2 and refractory in vivo to docetaxel. Larotaxel was first evaluated in vitro on human mammary UISO BCA-1 cell line, after a 96-hour incubation, using 14C-thymidine incorporation read-out. The IC50 of larotaxel (~ 3nM) was not significantly modified when combined to trastuzumab. Thereafter, in nude mice bearing UISO BCA-1, a 3 arm dose-response study was performed comparing the antitumor efficacy single agents and their combination. Mice bearing measurable (125 mg) tumors were treated iv with larotaxel (12.4, 20, 32.3 and 52.1 mg/kg/day, on days 17, 21, 25 post tumor implantation), or sc with trastuzumab (2.5, 10, 25 and 40 mg/kg/day, on days 17, 21, 25, 29). In the combination, each dose of larotaxel was combined with the dose-response of trastuzumab using the same schedule of administration as the single agents alone. Therapeutic synergism was declared when superior activity by at least 1 log cell kill (log CK = tumor growth delay / 3.32 x tumor doubling time) was observed with the combination in comparison with either of the single agents. At the Highest nonToxic Dose (HNTD) of 32.3 mg/kg/day (total dose 96.9 mg/kg), larotaxel, as a single agent, induced a 5% body weight loss (bwl) and was found active with a 1.3 log CK. Trastuzumab alone, at the highest dose tested, 40 mg/kg/day (total dose 160 mg/kg), was found inactive, although UISO BCA-1 xenografts overexpressed Her2. The HNTD of the combination (larotaxel at 32.3 mg/kg/day, with herceptin at 2.5 mg/kg/day), induced a 4 % bwl and exhibited a greater antitumor activity with 2.6 log CK, 6/8 complete regressions (regression below the limit of palpation) and 2/8 tumor free survivors on day 121. A good antitumor activity was maintained at the 5 combined dosages below the HNTD. In order to further explore this synergy between both agents, mechanistic studies are ongoing. In conclusion, the larotaxel- trastuzumab combination was found synergistic in mice bearing a human breast tumor refractory to docetaxel, as well as anthracycline and other agents. These data provide a good rationale for further clinical evaluation of this combination in breast cancer with Her2 overexpression.

PURPOSE:Combination treatment with radiotherapy and chemotherapy has emerged as the dominant form of cancer adjuvant regimens in recent years. Clofarabine, a newly approved drug for pediatric leukemia, is a second-generation purine nucleoside analogue that can block DNA synthesis and inhibit DNA repair. Therefore, we hypothesized that clofarabine could work synergistically with radiotherapy to increase the tumor cell response. METHODS AND MATERIALS:The effects of clofarabine on radiosensitivity have been established in several tumor cell lines in vitro and in vivo using colony-forming assays and tumor xenografts. The effect of clofarabine on the DNA damage response was also studied in vitro by measuring gamma-H2AX focus formation. RESULTS:Clonogenic survival was significantly reduced in irradiated cells treated with clofarabine, demonstrating the strong radiosensitizing effect of clofarabine. Furthermore, clofarabine displayed a radiosensitizing effect that was greater than gemcitabine or 5-fluorouracil. We also found that low doses of clofarabine can prolong the presence of radiation-induced gamma-H2AX nuclear focus formation, and high doses of clofarabine can induce DNA double-strand breaks, suggesting that clofarabine can interfere with DNA damage response pathways. In addition, clofarabine-induced radiosensitization was also established in vivo using a colorectal cancer model, DLD-1, in athymic nude mice. When combined with fractionated radiotherapy, a moderate dose of clofarabine led to a significant increase in tumor growth inhibition. CONCLUSION:Clofarabine acts as a powerful radiosensitizer both in vitro and in vivo by interfering with the DNA damage response.

Proc Amer Assoc Cancer Res, Volume 46, 2005 5876 Tasidotin HCl is a synthetic pentapeptide derivative of dolastatin-15 with a unique mechanism of action that potentially differs from that of microtubulin stabilizers (taxanes and epothilones) and tubulin inhibitors (vinca alkaloids). Tasidotin HCl at low concentrations inhibits microtubule nucleation or elongation which is likely to disrupt mitotic spindle formation and mitosis. The objective of the present investigation was to evaluate the in vivo activity of Tasidotin HCl against a wide variety of human cancer cell lines, including Hep-3B hepatic, Caki-1 renal, A-673 rhabdomyosarcoma, H-Meso-1 mesothelioma, RL lymphoma, and RPMI-8226 multiple myeloma. Treatment was initiated when median SC tumor size was approximately 150-200 mm3. Tasidotin HCl was administered IP daily times 5 for 2 weeks dosing regimen at 125, 62.5, and 31.25 mg/kg/day for all of the tumor lines, except for RL and RPMI-8226 (only high dosage administered). Tasidotin HCl was well tolerated (≤20% body weight loss or toxic deaths) at the 125 mg/kg/day dosage for the Caki-1 tumor cell line, and at the 62.5 and 31.25 mg/kg/day dosages for the remaining tumor lines. Tasidotin HCl was very effective against the A-673 rhabdomyosarcoma and H-Meso-1 mesothelioma xenografts producing median tumor growth delays (T-C) of >76.5 and >20.4 days, respectively, at the 62.5 mg/kg/day dosage level. In the A-673 rhabdomyosarcoma study, there were ten complete regressions in animals that remained tumor free at the conclusion of the study. Tasidotin HCl was moderately effective against Caki-1 renal cell carcinoma and Hep-3B hepatocellular xenografts producing median tumor growth delays of 10.5 and 9.5 days, respectively, at the 62.5 mg/kg/day dosage level. Tasidotin HCl at a dosage of 125 mg/kg/day was very active against RL and RPMI-8226 tumor xenografts with tumor growth delays of 49.4 and 30.8 days and 6/10 and 4/10 complete responses in surviving mice, respectively. Due to numerous toxic deaths, the RL and RPMI-8226 studies are currently being repeated at lower dosage levels. These data indicate that Tasidotin HCl has good antitumor activity in vivo against a variety of different types of tumor cell lines.