The impact of first-generation covalent KRASG12C inhibitors has been reduced due to the development of drug resistance, tolerability and challenges combining with immunotherapy. We designed olomorasib, a next-generation GDP-binding KRASG12C inhibitor, for nanomolar potency as well as selectivity over wild-type inhibition. In both in vitro and in vivo models of KRASG12C -mutant cancers, olomorasib reduces RAS activity and pERK levels, leading to substantial and significant tumor growth inhibition. Additionally, olomorasib combined with immune checkpoint inhibitors demonstrates greater anti-tumor activity compared to monotherapy. Furthermore, we demonstrate that olomorasib binds tightly to KRASG12C even in the presence of clinically relevant second site mutations, a known mechanism of resistance and limitation to currently approved KRASG12C inhibitors. These findings suggest that olomorasib could be effective for patients with KRASG12C mutant cancers either as monotherapy or in combination with immunotherapy. Olomorasib monotherapy and combination treatments are currently being investigated clinically.

KRAS is altered in ∼16% of all cancers and is an oncogenic driver in NSCLC, pancreatic, colorectal, and other cancers. Next generation KRAS inhibitors, designed to target multiple oncogenic KRAS mutations, have the potential to improve outcomes for the large burden of KRAS-mutated disease. Importantly, preclinical data suggest that a pan-KRAS approach that spares wildtype HRAS and NRAS may avoid the skin toxicities associated with pan-RAS inhibition.1 This is particularly important in the context of treating KRAS-mutated colorectal cancer in combination with EGFR inhibition, which also carries skin toxicity. Next generation KRAS inhibitors could treat a wide range of patients including the approximately 35% of those with NSCLC who are at increased risk of developing CNS metastases. LY4066434 is an orally bioavailable, highly potent pan-KRAS inhibitor that has high selectivity over HRAS and NRAS.2 Here, we report the antitumor activity of LY4066434 in patient-derived xenograft (PDX) and intracranial cancer models. We evaluated the activity of LY4066434 in PDX models harboring different KRAS mutations (both common and less frequent) and representing diverse histologies. LY4066434 showed robust anti-tumor activity, ranging from significant tumor growth inhibition to strong regression, in KRAS-driven PDX models of NSCLC, pancreatic, colorectal, and gastric cancers. Furthermore, we analyzed the activity of LY4066434 in combination with standard-of-care therapies. LY4066434 when combined with cetuximab showed enhanced antitumor activity in PDX models of NSCLC, pancreatic, and colorectal cancers with various KRAS mutations. Additionally, the combination of LY4066434 with chemotherapies also demonstrated greater efficacy in KRAS-mutant PDX models of endometrial and ovarian cancers. Finally, evaluation of LY4066434 activity in two KRAS-mutant orthotopic brain tumor models of NSCLC showed that LY4066434 inhibited tumor growth and promoted survival in these brain tumor models. Taken together, these results demonstrate the potential of LY4066434 as a promising therapeutic option for a range of cancer types driven by KRAS mutations including NSCLC, pancreatic, and colorectal cancers. LY4066434 is currently being investigated clinically (NCT06607185). 1. Manousaridis I. et al. 2013. J Eur Acad Dermatol and Venereol, 27: 11-18. 2. 2. Prieto L. et al. AACR-NCI-EORTC. Oct 11-15, 2023. Boston, MA. Hong Gao, Youyan Zhang, Chun Ping Yu, Wei Guo Xu, Binghui Li, Huimin Bian, Manuj Tandon, Tao Wang, Trent R. Stewart, Mark H. Bender, Wenyu Ming, Megan A. Johnson, Lisa M. Kays, Madeleine Leonard, Mark A. Castanares, Andrew Capen, Arthur Xintian You, Wen Ting Bian, Lourdes Prieto, Timothy Kercher, Laurie LeBrun, Anke Klippel, Chandrasekar Iyer, Xueqian Gong. LY4066434, an oral small molecule pan-KRAS inhibitor, demonstrates robust anti-tumor activity in KRAS-mutant models, including in the CNS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4375.

Abstract KRAS G12D mutations are activating oncogenic events that occur in approximately 35%, 13%, and 4% of pancreatic, colorectal, and non-small cell lung cancers, respectively, and less commonly in other cancers. We previously demonstrated that LY3962673 is a highly potent inhibitor of KRAS G12D and is selective against wild-type (WT) KRAS in mutant -cell lines and -in vivo models. Here, we describe the mechanism by which LY3962673 inhibits KRAS G12D and report a more comprehensive evaluation of LY3962673 activity across a panel of genetically and histologically diverse cancer cell lines, as well as in multiple patient-derived xenograft (PDX) models. LY3962673 is a non-covalent KRAS G12D inhibitor with high affinity binding to KRAS G12D-GDP (Kd 0.071 nM) compared to KRAS G12D-GTPγS (Kd 26.7 nM). In a panel of cancer cell lines with KRAS G12D mutations, non-G12D mutations or KRAS WT, LY3962673 selectively suppressed MAPK signaling and inhibited the growth of KRAS G12D mutant cancer cells while sparing KRAS WT and non-G12D mutant cells. Sensitivity to LY3962673 varied among the KRAS G12D-mutant cells tested, suggesting that not all cell lines share the same dependence on KRAS G12D for their growth and survival. Furthermore, in multiple KRAS G12D-mutant PDX models representing diverse tumor types, LY3962673 demonstrated anti-tumor activities, ranging from tumor growth inhibition to robust tumor regression. LY3962673 also showed enhanced efficacy when combined with other anti-cancer agents. Taken together, the findings underscore the potential of LY3962673 as a monotherapy or in combination with other anti-cancer agents, as a promising oral therapeutic option for a range of cancer types with KRAS G12D mutations. Citation Format: Xueqian Gong, Hong Gao, Mark H. Bender, Wenyu Ming, Youyan Zhang, Trent R. Stewart, Chun Ping Yu, Wei Guo Xu, Aurthur Xintian You, Wen Ting Bian, Binghui Li, Tao Wang, Huimin Bian, Manuj Tandon, Andrew Capen, Rachel N. Cavitt, Bryan D. Anderson, Wayne Bocchinfuso, Anke Klippel, Chandrasekar Iyer. LY3962673, an oral, highly potent, mutant-selective, and non-covalent KRAS G12D inhibitor demonstrates robust anti-tumor activity in KRAS G12D models [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 3316.

Supplementary Figure S1. Validation of BRAF deletion in BxPC-3 cells by Sanger's sequencing method. Supplementary Figure S2. BRAF deletion (deltaBRAF), but not WT BRAF, is able to transform cells. Supplementary Figure S3. Validation of in situ PLA in HeLa and HEK293 cells. Supplementary Figure S4. Phospho-CRAF and MAPK activation in selected tumor cells with BRAF alteration or KRAS mutation. Supplementary Figure S5. Phospho-MEK and ERK inhibition by dabrafenib in tumor cells harboring BRAF deletion. Supplementary Figure S6. In vitro effects of MAPK inhibitors on tumor cells harboring BRAF deletions. Supplementary Table S1. Novel somatic BRAF in-frame deletions from cancer cell lines and patient samples. Supplementary Figure S7. LY3009120, but not vemurafenib, exhibited significant tumor growth inhibition and regression in lung and pancreatic tumor xenograft models harboring the BRAF deletions without significant body weight loss. Supplementary Table S2. IC50 of LY3009120 and vemurafenib against tumor cells with atypical BRAF mutations.

Supplementary figure S1 describes the molecular mechanisms of resistance across vemurafenib-resistant cell line models. Supplementary figure S2 serves as a repeat of figure 3a describing development of in vivo model of resistance, and demonstrates the effect of vemurafenib withdrawl on the resistant tumors. Supplementary figure S3 describes the effect of vemurafenib treatment on MAPK pathway inhibition in A375-RV2 cells. Supplementary figure S4 shows that selective cyclin D1 knockdown or CDK4/6 inhibition induces apoptosis in A375-R1 and M14-R vemurafenib-resistant melanoma cells.

Supplementary table S1 describes the copy number variations in A375-R1 and A375 parental cells. Supplementary figure legends describe supplementary figures S1-3.

Although KRAS has long been considered undruggable, direct KRASG12C inhibitors have shown promising initial clinical efficacy. However, the majority of patients still fail to respond. Adaptive feedback reactivation of RAS-mitogen-activated protein kinase (MAPK) signaling has been proposed by our group and others as a key mediator of resistance, but the exact mechanism driving reactivation and the therapeutic implications are unclear. We find that upstream feedback activation of wild-type RAS, as opposed to a shift in KRASG12C to its active guanosine triphosphate (GTP)-bound state, is sufficient to drive RAS-MAPK reactivation in a KRASG12C-independent manner. Moreover, multiple receptor tyrosine kinases (RTKs) can drive feedback reactivation, potentially necessitating targeting of convergent signaling nodes for more universal efficacy. Even in colorectal cancer, where feedback is thought to be primarily epidermal growth factor receptor (EGFR)-mediated, alternative RTKs drive pathway reactivation and limit efficacy, but convergent upstream or downstream signal blockade can enhance activity. Overall, these data provide important mechanistic insight to guide therapeutic strategies targeting KRAS.

坳陷湖盆大型浅水三角洲是目前中国陆上岩性油气藏规模储量增长的主体.通过对松辽盆地南部上白垩统保乾三角洲和现代鄱阳湖赣江三角洲解剖,重点探讨湖盆浅水三角洲形成的地质背景、沉积特征与生长模式.结果表面:①坳陷湖盆具有形成大型浅水三角洲的沉积背景,敞流型湖盆导致的湖平面频繁升降控制了浅水三角洲的纵横向发育规模.②松辽盆地南部上白垩统发育2种不同类型的三角洲,深湖型三角洲一般呈朵叶状,沉积亚相展布清晰,沉积微相以分流河道、河口坝和分流河道间为主;浅湖型三角洲一般呈鸟足状或树枝状,沉积亚相分异不明显,沉积微相以分流河道和分流河道间为主,河口坝不发育;③通过现代沉积遥感定量分析,刻画了鄱阳湖赣江中支三角洲近50年的发育特征和演化规律,揭示了分流河道从分散树枝状到闭合结网状的生长过程.④坳陷湖盆大型浅水三角洲是不断发育的多期朵叶体在平面上拼接而成的复合体,其中分流河道是最重要的储集砂体类型,在平面上呈结网状分布,控制了大面积岩性油气藏的分布与富集.

KRAS-G12C is an important oncogenic mutation in patients with NSCLC, CRC, and other cancer types. Currently, there are no FDA-approved KRAS-G12C inhibitors, and those in clinical development have relatively modest activity compared to other approved therapies targeting other classic oncogenic drivers. This modest activity may be potentially due in part to incomplete target occupancy and trapping of mutant KRAS in the inactive GDP-bound state. Achieving maximal clinical benefit in patients harboring a KRAS-G12C mutation, may require a potent inhibitor capable of achieving near complete target engagement. Here, we report the identification of LY3537982, a novel, highly selective and potent inhibitor of the KRAS-G12C protein, discovered using structure-based design. In kinetic studies, LY3537982 showed a high Kinact/Ki value (248,016 M-1 s-1), compared to AMG510 (7,220 M-1 s-1) and MRTX849 (35,000 M-1 s-1). LY3537982 inhibited KRAS-GTP loading with an IC50 value of 3.35 nM in the KRAS-G12C mutant H358 lung cancer cell line, while AMG510 and MRTX849 had IC50 values of 47.9 nM and 89.9 nM, respectively. LY3537982 also inhibited phospho-ERK in H358 cells with an IC50 value of 0.65 nM, while the IC50 values of AMG510 and MRTX849 were 13.5 nM and 14 nM, respectively. In a panel of cancer cell lines with KRAS-G12C or non-G12C mutations, LY3537982 selectively inhibited the growth of KRAS-G12C mutant tumor cells and not KRAS wild-type or non-G12C mutant cells. Sensitivity to LY3537982 varied among the KRAS-G12C mutant cells tested, suggesting that not all cell lines maintain the same dependence on KRAS-G12C. Similarly, in multiple xenograft or patient-derived xenograft (PDX) models harboring a KRAS-G12C mutation, LY3537982 exhibited a range of anti-tumor activity from complete regression to significant tumor growth inhibition, at 3 to 30 mg/kg QD or BID. Mechanism-based combinational screens have also identified certain targeted therapies that can synergize with LY3537982 to achieve better anti-tumor activity in vitro and in vivo, including abemaciclib, the selective AurA inhibitor LY3295668, and cetuximab. Together these data suggest that in certain biologic contexts, broader and more durable anti-tumor activity could be achieved with combination regimens. A first-in-human Phase 1 clinical trial is planned for 2021. Citation Format: Sheng-Bin Peng, Chong Si, Youyan Zhang, Robert D. Van Horn, Xi Lin, Xueqian Gong, Lysiane Huber, Gregory Donoho, Carmen Curtis, John M. Strelow, Wayne P. Bocchinfuso, Deqi Guo, Serge L. Boulet, David Barda, Danalyn Manglicmot, Melbert-Brian D. Saflor, Jing Wang, Junpeng Xiao, Michael J. Chalmers, Lee Burns, Ryan J. Linder, Bradley L. Ackermann, Paul D. Cornwell, Lian Zhou, Denis McCann, James Henry. Preclinical characterization of LY3537982, a novel, highly selective and potent KRAS-G12C inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1259.

Shale oil and gas resources are abundant all over the world. TOC (Total Organic Carbon) content is an important index of shale evaluation. TOC content in organic shale is usually obtained through the shale physics experiment. In this paper we discussed a new method of TOC content prediction in organic shale using laser intensity of terrestrial laser scanning. Firstly, we studied on the correlation relationship between TOC content and laser intensity. Then we built the exponential relationship model between TOC content and laser intensity using exponential fitted methods to predict TOC content. Chang7 shale of Yanchang Formation is one of high-quality source rocks in Erdos Basin, China. So, Chang7 shale was used for testing the TOC content prediction method in shale in this paper. Experiments showed that laser intensity can efficiently predict TOC content in shale. This method can be used to directly predict TOC content in field outcrops of organic shale.

在前人研究工作的基础上,从遥感地质的角度对钱家店铀矿区进行了再认识.发现钱家店铀矿区在褶皱抬升之后,发生了断块隆起,形成断隆构造,控制了本区的铀成矿后生改造和多期成矿作用.认为钱家店铀矿区的成矿演化,经历了断陷→坳陷→褶皱抬升→断块隆起几个阶段,提出本区的构造反转成矿不限于前人认为的褶皱抬升和断层上下的反向错动,更具成矿意义的是断陷向断隆的构造反转.依据上述认识,探讨了开鲁坳陷进一步区域找铀矿的新思路和遥感地质的具体做法.

In order to obtain macroscopic and quantitative porosity data in outcrop rapidly, a new Hyperspectrum based porosity estimation method was proposed in this paper. Sandstone samples were collected from field outcrop and measured for porosity data, whose influence factors were analyzed with rock thin section. After the preprocessing on the spectral data of rock samples, the spectral response mechanism of porosity was preliminarily explored. Considering the high dimensionality of spectral bands and the multiple correlation between bands, the porosity estimation models were constructed using the partial least squares method. The important bands in the model were indicated by the variable importance in the projection. The results show that: sandstone porosity can be indirectly retrieved based on the correlation between interstitial fillings and porosity and the spectral characteristics of interstitial fillings; sandstone porosity shows good spectral response; reflectance has the ability to estimate porosity quantitatively ( porosity estimation model based on full wavelengths: R-2 = 0.72, RMSE = 2.28, RPD = 1.94); the important bands help to reduce the independent variable dimension and find the porosity-sensitive spectral response. This study lays the foundation for porosity characterization in the outcrop based on hyperspectral images.

Activating mutations in the KRAS and BRAF genes, leading to hyperactivation of the RAS/RAF/MAPK oncogenic signaling cascade, are common in patients with colorectal cancer (CRC). While selective BRAF inhibitors are efficacious in BRAFmut melanoma, they have limited efficacy in BRAFmut CRC patients. In a RASmut background, selective BRAF inhibitors are contraindicated due to paradoxical activation of the MAPK pathway through potentiation of CRAF kinase activity. A way to overcome such paradoxical activation is through concurrent inhibition of the kinase activity of both RAF isoforms. Here, we further examined the effects of LY3009120, a panRAF and RAF dimer inhibitor, in human models of CRC with various mutational backgrounds. We demonstrate that LY3009120 induced anti-proliferative effects in BRAFmut and KRASmut CRC cell lines through G1-cell cycle arrest. The anti-proliferative effects of LY3009120 in KRASmut CRC cell lines phenocopied molecular inhibition of RAF isoforms by simultaneous siRNA-mediated knockdown of ARAF, BRAF and CRAF. Additionally, LY3009120 displayed significant activity in in vivo BRAFmut and KRASmut CRC xenograft models. Examination of potential resistance to LY3009120 demonstrated RAF-independent ERK and AKT activation in the KRASmut CRC cell line HCT 116. These findings describe the preclinical activity of a panRAF inhibitor in a BRAFmut and KRASmut CRC setting.

KRAS, NRAS and BRAF mutations are among the most important oncogenic drivers in many major cancer types, such as melanoma, lung, colorectal and pancreatic cancer. There is currently no effective therapy for the treatment of RAS mutant cancers. LY3009120, a pan-RAF and RAF dimer inhibitor advanced to clinical study has been shown to inhibit both RAS and BRAF mutant cell proliferation in vitro and xenograft tumor growth in vivo. Abemaciclib, a CDK4/6-selective inhibitor, is currently in phase III studies for ER-positive breast cancer and KRAS mutant lung cancer. In this study, we found that combinatory treatment with LY3009120 and abemaciclib synergistically inhibited proliferation of tumor cells in vitro and led to tumor growth regression in xenograft models with a KRAS, NRAS or BRAF mutation at the doses of two drugs that were well tolerated in combination. Further in vitro screen in 328 tumor cell lines revealed that tumor cells with KRAS, NRAS or BRAF mutation, or cyclin D activation are more sensitive, whereas tumor cells with PTEN, PIK3CA, PIK3R1 or retinoblastoma (Rb) mutation are more resistant to this combination treatment. Molecular analysis revealed that abemaciclib alone inhibited Rb phosphorylation partially and caused an increase of cyclin D1. The combinatory treatment cooperatively demonstrated more complete inhibition of Rb phosphorylation, and LY3009120 suppressed the cyclin D1 upregulation mediated by abemaciclib. These results were further verified by CDK4/6 siRNA knockdown. Importantly, the more complete phospho-Rb inhibition and cyclin D1 suppression by LY3009120 and abemaciclib combination led to more significant cell cycle G(0)/G(1) arrest of tumor cells. These preclinical findings suggest that combined inhibition of RAF and D-cyclin-dependent kinases might provide an effective approach to treat patients with tumors harboring mutations in RAS or RAF genes.

Abstract We have identified previously undiscovered BRAF in-frame deletions near the αC-helix region of the kinase domain in pancreatic, lung, ovarian, and thyroid cancers. These deletions are mutually exclusive with KRAS mutations and occur in 4.21% of KRAS wild-type pancreatic cancer. siRNA knockdown in cells harboring BRAF deletions showed that the MAPK activity and cell growth are BRAF dependent. Structurally, the BRAF deletions are predicted to shorten the β3/αC-helix loop and hinder its flexibility by locking the helix in the active αC-helix-in conformation that favors dimer formation. Expression of L485-P490–deleted BRAF is able to transform NIH/3T3 cells in a BRAF dimer–dependent manner. BRAF homodimer is confirmed to be the dominant RAF dimer by proximity ligation assays in BRAF deletion cells, which are resistant to the BRAF inhibitor vemurafenib and sensitive to LY3009120, a RAF dimer inhibitor. In tumor models with BRAF deletions, LY3009120 has shown tumor growth regression, whereas vemurafenib is inactive. Significance: This study discovered oncogenic BRAF deletions with a distinct activation mechanism dependent on the BRAF dimer formation in tumor cells. LY3009120 is active against these cells and represents a potential treatment option for patients with cancer with these BRAF deletions, or other atypical BRAF mutations where BRAF functions as a dimer. Cancer Discov; 6(3); 300–15. ©2016 AACR. This article is highlighted in the In This Issue feature, p. 217

It is of great importance for petroleum exploration to study the sedimentary features and the growth pattern of shoal water deltas in lake basins. Taking spatio-temporal remote sensing images as the principal data source, combined with field sedimentation survey, a quantitative research on the modern deposition of Ganjiang delta in the Poyang Lake Basin is described in this paper. Using 76 multi-temporal and multi-type remote sensing images acquired from 1973 to 2015, combined with field sedimentation survey, remote sensing interpretation analysis was conducted on the sedimentary facies of the Ganjiang delta. It is found that that the current Poyang Lake mainly consists of three types of sand body deposits including deltaic deposit, overflow channel deposit, and aeolian deposit, and the distribution of sand bodies was affected by the above three types of depositions jointly. The mid-branch channels of the Ganjiang delta increased on an exponential growth rhythm. The main growth pattern of the Ganjiang delta is dendritic and reticular, and the distributary channel mostly arborizes at lake inlet and was reworked to be reticulatus at late stage.

LY3009120 is a pan-RAF and RAF dimer inhibitor that inhibits all RAF isoforms and occupies both protomers in RAF dimers. Biochemical and cellular analyses revealed that LY3009120 inhibits ARAF, BRAF, and CRAF isoforms with similar affinity, while vemurafenib or dabrafenib have little or modest CRAF activity compared to their BRAF activities. LY3009120 induces BRAF-CRAF dimerization but inhibits the phosphorylation of downstream MEK and ERK, suggesting that it effectively inhibits the kinase activity of BRAF-CRAF heterodimers. Further analyses demonstrated that LY3009120 also inhibits various forms of RAF dimers including BRAF or CRAF homodimers. Due to these unique properties, LY3009120 demonstrates minimal paradoxical activation, inhibits MEK1/2 phosphorylation, and exhibits anti-tumor activities across multiple models carrying KRAS, NRAS, or BRAF mutation.

为了改进传统露头研究方法的不足,以及客观、全面地认识露头所揭示的地质信息,将激光雷达技术应用到露头地层成图研究中,并利用计算机技术实现地层图像可视化,形成了鄂尔多斯盆地上三叠统延长组杨家沟剖面数字露头.基于数字露头开展上三叠统延长组长3油层组层序地层、沉积旋回和砂体展布等地质信息的提取与分析,并利用典型层序界面识别标志,结合层序地层学理论,在数字露头上进行层序边界识别和层序界面追踪,划分出1个四级层序界面,其界面之下地层岩性表现为反旋回,界面之上地层岩性表现为正旋回,层序界面对应的位置砂体最厚.通过建立研究区沉积旋回的识别标志,在数字露头上进行沉积旋回界面的追踪与对比,识别出了3个不对称式短期旋回,这3个短期旋回又可组成1个四级基准面上升半旋回,为一套整体向上变细的四级准层序组,其砂体厚度向上具有减小的趋势.通过建立砂体解释标志,分别在四级基准面旋回底部和剖面顶部识别出了典型的河道砂体,进而对露头解剖的单砂体内部砂层进行了精细刻画与对比.总体认为,剖面岩性以细砂岩和粗粉砂岩为主,局部夹暗色泥岩和页岩;砂体侧向迁移,在垂向上呈多期叠置关系,横向上变化较大.

The RAS-RAF-MEK-MAPK cascade is an essential signaling pathway, with activation typically mediated through cell surface receptors. The kinase inhibitors vemurafenib and dabrafenib, which target oncogenic BRAF V600E, have shown significant clinical efficacy in melanoma patients harboring this mutation. Because of paradoxical pathway activation, both agents were demonstrated to promote growth and metastasis of tumor cells with RAS mutations in preclinical models and are contraindicated for treatment of cancer patients with BRAF WT background, including patients with KRAS or NRAS mutations. In order to eliminate the issues associated with paradoxical MAPK pathway activation and to provide therapeutic benefit to patients with RAS mutant cancers, we sought to identify a compound not only active against BRAF V600E but also wild type BRAF and CRAF. On the basis of its superior in vitro and in vivo profile, compound 13 was selected for further development and is currently being evaluated in phase I clinical studies.

Abstract BRAF mutations, particularly the somatic hot spot BRAF V600E mutation, were discovered as major oncogenic mutations in many cancer types. It was shown that BRAF V600E is a potent oncogene that activates the MAPK pathway and functions as a BRaf monomer. BRaf selective inhibitors, vemurafenib and dabrafenib, which are effective in inhibiting the kinase activity of BRaf monomer, have demonstrated robust anti-tumor activities in BRAF mutant xenograft models and significant clinical benefit among BRAF mutant melanoma patients. In this study, we have identified and characterized novel BRaf aberrant variants, which have in-frame deletions within or adjacent to the L485-P490 region in patient samples and/or cell lines of lung, pancreatic, and ovarian cancers. Tumor cells with these endogenous BRaf deletions are resistant to BRaf monomer inhibitor vemurafenib based on inhibition of phospho-MEK and phospho-ERK, cell proliferation, and cell cycle progression. However, these cells are sensitive to LY3009120, a pan Raf and Raf dimer inhibitor. Further analysis using siRNA showed that the MEK-ERK activity in these cells is mainly dependent on BRaf, not CRaf or ARaf. Ectopical expression of the L485-P490 deleted BRaf in mouse NIH3T3 cells is able to transform the cells and form colonies comparable to BRaf V600E mutation in three-dimensional soft agar growth. More importantly, the Raf dimer disrupting mutation BRafR509H abolished the transforming activity of the L485-P490 deleted BRaf, suggesting that this BRaf deletion functions as a dimer. Further, ectopical expression of the L485-P490 deleted BRaf promotes primarily BRaf homodimerization as revealed by proximity ligation assays (PLA). It was also confirmed by PLA that BRaf homodimer is the dominant form of Raf dimers in tumor cells harboring these BRaf deletions. In lung and pancreatic tumor xenograft models developed with tumor cells with these BRaf deletions, LY3009120 treatment demonstrated significant tumor growth inhibition and regression, whereas vemurafenib treatment showed no in vivo activity. Overall, we have identified novel oncogenic BRaf deletions that function as BRaf homodimer and are sensitive to pan Raf and Raf dimer inhibitor LY3009120. Citation Format: Shih-Hsun Chen, Sean Buchanan, Youyan Zhang, Robert Van Horn, Tinggui Yin, Vipin Yadav, Swee Seong Wong, Lysiane Huber, James Henry, Ilaria Conti, James J. Starling, Gregory D. Plowman, Sheng-Bin Peng. Novel oncogenic BRaf deletions functioning as BRaf homodimer and sensitive to inhibition by LY3009120, a pan Raf and Raf dimer inhibitor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2142. doi:10.1158/1538-7445.AM2015-2142