BACKGROUND:PD-L1 is associated with poor efficacy of first- or second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in untreated EGFR-mutant non-small-cell lung cancer (NSCLC). Whether PD-L1 is also predictive of osimertinib efficacy in pre-treated patients with an acquired EGFR T790 M mutation is unclear. PATIENTS AND METHODS:PD-L1 expression and tumor microenvironments were evaluated in tumors from EGFR-mutant T790 M + NSCLC patients treated with osimertinib. In vitro and in vivo experiments were also performed to examine the effect of PD-L1 overexpression on osimertinib susceptibility in EGFR T790 M + cells. RESULTS:A total of 134 pre-treated EGFR T790 M + patients were enrolled, of whom 72 had del19, 58 had L858R, and 4 had G719X as initial EGFR mutation subtype. Positive PD-L1 expression (TC ≥ 1%) was found in 21 of 134 (15.7%) patients. PD-L1 expression did not differ across different biopsied sites and among different EGFR mutation subgroups. Kaplan-Meier estimate revealed no significant difference in progression-free survival (PFS) in PD-L1-positive versus PD-L1-negative patients. Multivariate analysis using the Cox proportional hazard model found that older age and L858R mutation were independent predictive factors. Multiplex IHC showed that immune cell infiltration was not associated with PD-L1 expression or osimertinib treatment response. By overexpressing PD-L1 in EGFR T790 M + cells, we found that PD-L1 did not result in osimertinib resistance in in vitro and xenograft models. CONCLUSION:PD-L1 expression in pre-treated EGFR T790 M + lung adenocarcinoma is not predictive of osimertinib efficacy, as demonstrated by in vitro, xenograft, and clinical case studies.

Abstract High expression of programmed death-ligand 1(PD-L1) is associated with poor survival outcomes in epidermal growth factor receptor (EGFR) mutation non-small cell lung cancer (NSCLC) patients receiving EGFR tyrosine kinase inhibitors (EGFR-TKIs). In this study we aimed to determine how increased PD-L1 affects the signal transduction of EGFR-mutant NSCLC cells. We first established PD-L1 overexpression EGFR mutant NSCLC cells, and discovered that PD-L1 overexpression cells had upregulated c-MET phosphorylation compared with parental cells using receptor tyrosine kinase array study. Subsequently, we demonstrated that knocking out PD-L1 (CD 274) in EGFR mutant NSCLC cells resulted in down-regulation of c-MET phosphorylation. Since protein tyrosine phosphatases (PTP) are known key regulators for c-MET phosphorylation and dephosphorylation, the activity of PTP was assessed. In PD-L1 overexpression EGFR mutant NSCLC cells, the PTP activity was decreased, whereas in PD-L1 knock-out cells, the PTP activity was increased. Additionally, the downregulation of c-MET phosphorylation in PD-L1 knock-out cells could be restored by adding PTP inhibitor (Na3VO4). The gene expression analysis showed that PTP expression was down-regulated in PD-L1 overexpression cells, indicating that PD-L1 upregulates c-MET phosphorylation by reducing PTP expression. We further established xenograft animal models using NSCLC cells with strong baseline c-MET phosphorylation to determine the effect of c-MET phosphorylation on osimertinib (a 3rd-generation EGFR-TKI) treatment. We found that tumor cells with strong c-MET phosphorylation were prone to develop MET amplification as acquired resistance under osimertinib, which could be overcome with combination of osimertinib and tepotinib, a c-MET inhibitor. Taken together, our results expand our understanding of PD-L1’s role beyond an immune checkpoint in EGFR mutant NSCLC. PD-L1-regulated MET alterations could be a crucial mechanism leading to poor treatment outcome of EGFR-TKIs in PD-L1 overexpression EGFR mutant NSCLC. Citation Format: Derek De-Rui Huang, Chia-Chi Hsu, Wei-Hsun Hsu, Bin-Chi Liao, James Chih-Hsin Yang. Programmed death-ligand 1 (PD-L1) upregulates c-MET phosphorylation via protein tyrosine phosphatase and contributes to the development of MET amplification in epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer [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 6972.

Background: PD-L1 is associated with poor efficacy of first- and second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in frontline treatment of EGFR-mutant non-small-cell lung cancer (NSCLC). Whether PD-L1 is also predictive of osimertinib efficacy in pre-treated patients with an acquired EGFR T790M mutation is unclear.Patients and Methods: EGFR-mutant NSCLC patients who acquired a T790M mutation after progression on first- or second-generation TKIs and then received osimertinib treatment were retrospectively enrolled. The re-biopsied tissues before osimertinib were stained for PD-L1 expression using a Ventana SP263 antibody. The treatment responses and clinical outcomes were analyzed and correlated with PD-L1 expression. Multiplex immunohistochemical (IHC) staining was used for tumor microenvironment evaluation.Results: A total of 134 patients were enrolled in our study, of whom 72 had del19, 58 had L858R, and 4 had G719X as the initial EGFR mutation subtypes. Positive PD-L1 expression (TPS ≥1%) was found in 21 of 134 (15.7%) patients. The proportion of PD-L1 positivity was similar in different biopsied sites (p=0.428), and there was no difference between del19/T790M and L858R/T790M tumors (PD-L1 ≥1% in del19/T790M vs L858R/T790M: 12/74, 6/58, p=0.114). The Kaplan Meier estimate revealed no significant difference in progression-free survival (PFS) in PD-L1-positive versus PD-L1-negative patients, and multivariate analysis using the Cox proportional hazard model found that only age (≥70 vs <70, HR 0.674, 95% CI 0.458~0.993, p=0.046) and L858R (vs del19, HR 1.551, 95% CI 1.043~2.307, p=0.030) were independently predictive of PFS, while liver metastases was an independent poor prognostic factor for overall survival. Multiplex IHC in 30 cases showed that cell densities of each immune cell were not associated with PD-L1 expression or osimertinib efficacy.Conclusions: Unlike first- or second-generation EGFR TKI, the PFS with osimertinib did not show any correlation with PD-L1 expression in EGFR T790M+ NSCLC.

Abstract Pulmonary lymphoepithelial carcinoma (LEC) is a rare type of lung cancer. Though the clinical outcomes of patients with LEC are better than those for patients with other types of lung cancer, tumors frequently recur. Evidence has indicated that the immune microenvironment factors may predict outcome of cancer therapy; however, the composition of immune microenvironment in LEC remains largely unknown. We investigated the association between the immune microenvironment of LEC by using multiplex immunohistochemical staining. The densities of each tumor-infiltrating immune cell type and the amount of infiltrating immune cells spatially proximal to the closet tumor cell were analyzed. Although there was no significant correlation between the clinical outcome of LEC and the density of each tumor-infiltrating immune cell type, we found that the amount of CD4 + T lymphocyte proximal to tumor positively trended to longer disease-free survival in LEC. Additionally, the PD-L1 tumor proportion score was highly correlated with the amount of CD8 + T lymphocyte proximal to tumor, suggesting that immunotherapy might be beneficial for LEC patients. The spatial proximity of tumor-infiltrating immune cell measurement is useful for investigating the tumor-immune cells interaction. The spatial proximity of tumor-infiltrating CD4 + T lymphocytes might serve as a good prognostic factor for LEC.

Epidermal growth factor receptor (EGFR) mutations are the most common driver genes in non-small cell lung cancer (NSCLC), especially in the Asian population. Although EGFR-tyrosine kinase inhibitors (TKIs) are influential in the treatment of EGFR-mutant NSCLC patients, acquired resistance inevitably occurs. Therefore, there is an urgent need to develop strategies to overcome this resistance. In addition, cancer cells with particular mutations appear more vulnerable to deficiency related to the availability of specific amino acids. However, it is still unknown which amino acid is affected in the case of EGFR-mutant NSCLC. In the present study, we established a screening platform based on amino acid deprivation and found that EGFR-mutant NSCLC cells are sensitive to short-term lysine deprivation. Moreover, we found that expression of the gene for the lysine catabolism enzyme α-aminoadipate aminotransferase (AADAT) increased under lysine deprivation, revealing that AADAT can be regulated by EGFR–AKT signaling. Finally, we found that lysine reduction can not only enhance the cytostatic effect of single-agent osimertinib but also overcome the resistance of EGFR-TKIs in EGFR-mutant NSCLC cells. In summary, our findings suggest that the introduction of lysine stress might act as an advancement in EGFR-mutant NSCLC therapy and offer a strategy to overcome EGFR-TKI resistance.

Activated epidermal growth factor receptor (EGFR) has been proposed in the pathophysiology of neurodegenerative diseases. In the present study, the anti-inflammatory effect of afatinib, an EGFR-tyrosine kinase inhibitor (EGFR-TKIs) was investigated using CTX-TNA2 cells and primary cultured astrocytes subjected to oxygen/glucose deprivation (OGD). We found that OGD induced EGFR phosphorylation and activated subsequent signaling pathways, including phosphorylation of AKT and extracellular signal-regulated kinases (ERK). Afatinib blocked OGD-induced phosphorylation of EGFR, AKT and ERK. At the same time, afatinib attenuated OGD-induced elevations in glial fibrillary acidic protein (a biomarker of activated astrocytes) and proliferating cell nuclear antigen expression (a cell proliferating biomarker) as well as hypoxia-induced migratory ability. Furthermore, afatinib decreased OGD-induced increases in cyclooxygenase-II and inducible nitric oxide synthase expression of the treated astrocytes as well as NO content in the culture medium. Moreover, afatinib attenuated OGD-induced caspase 1 activation (a biomarker of inflammasome activation) and interleukin-1β levels (a pro-inflammatory cytokine). Collectively, afatinib could block OGD-induced EGFR activation and its downstream signaling pathways in astrocytes. Moreover, afatinib attenuated OGD-induced astrocyte activation, proliferation and inflammasome activation. These data support the involvement of EGFR activation in neuroinflammation. Furthermore, EGFR-TKIs may be promising in inhibiting neuroinflammation in the CNS neurodegenerative diseases.

Gallic acid (3,4,5-trihydroxybenzoic acid, GA), a phenolic acid, is ubiquitous in almost all parts of the plant. In the present study, a neuroinflammatory rat model using intranigral infusion of lipopolysaccharides (LPS, 4 μg/μL) was employed to study the neuroprotective effect of GA which was orally administered daily. Compared with the vehicle-treated rats, systemic administration of GA (100 mg/kg) significantly attenuated LPS-induced increases in glial fibrillary acidic protein (a biomarker of activated astrocytes) and ED-1 (a biomarker of activated microglia), as well as inducible nitric oxide synthase (iNOS, a proinflammatory enzyme) and interleukin-1β (a proinflammatory cytokine), in the LPS-infused substantia nigra (SN) of rat brain. At the same time, GA attenuated LPS-induced elevation in heme oxygenase-1 level (a redox-regulated protein) and α-synuclein aggregation (a hallmark of CNS neurodegeneration), suggesting that GA is capable of inhibiting LPS-induced oxidative stress and protein conjugation. Furthermore, GA prevented LPS-induced caspase 3 activation (a biomarker of programmed cell death) and LPS-induced increases in receptor-interacting protein kinase (RIPK)-1 and RIPK-3 levels (biomarkers of necroptosis), indicating that GA inhibited LPS-induced apoptosis and necroptosis in the nigrostriatal dopaminergic system of rat brain. Moreover, an in vitro study was employed to investigate the anti-inflammatory effect of GA on BV2 microglial cells which were subjected to LPS (1 μg/mL) treatment. Consistently, co-incubation of GA diminished LPS-induced increases in iNOS mRNA and iNOS protein expression in the treated BV-2 cells as well as NO production in the culture medium. The anti-oxidative activity of GA was evaluated using iron-induced lipid peroxidation of brain homogenates. After 3-h incubation at 37 °C, GA was more potent than glutathione and less potent than trolox in inhibiting iron-induced lipid peroxidation. Conclusively, the present study suggests that GA is anti-inflammatory via attenuating LPS-induced neuroinflammation, oxidative stress, and protein conjugation. Furthermore, GA prevented LPS-induced programmed cell deaths of nigrostriatal dopaminergic neurons of the rat brain, suggesting that GA may be neuroprotective by attenuating neuroinflammation in CNS neurodegenerative diseases.

BACKGROUNDProgrammed death-ligand 1 (PD-L1) expression is associated with clinical outcomes of epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma (ADC) treated with tyrosine kinase inhibitors (TKIs). However, whether PD-L1 expression plays a role in anaplastic lymphoma kinase (ALK)-positive lung ADC is unknown. We aimed to evaluate the impact of PD-L1 in patients with ALK-positive lung ADC receiving crizotinib.MATERIALS AND METHODSPD-L1 expression was identified by immunohistochemistry (IHC). Reverse transcriptase-polymerase chain reaction was used for ALK variant detection, and immunofluorescence-based multiplex staining was applied for exploring immune cells in tumor microenvironments.RESULTSA total of 78 patients with ALK-positive advanced ADC were enrolled in our study, of whom 52 received crizotinib. Compared with EGFR/ALK wild-type tumors, PD-L1 expression was lower in ALK-positive ADC. ALK fusion variants were identified in 32 patients, and those with variant 3 and 5 (short variants) had higher PD-L1 expression than those with other variants. The crizotinib objective response rate (ORR) and progression-free survival (PFS) was better in tumors with negative PD-L1 expression (ORR/PFS in PD-L1 0% vs. 1%-49% vs. 50%-100%: 60.7%/11.8 months vs. 38.5%/6.5 months vs. 36.4%/4.0 months, p = .007/.022). The multivariate Cox proportional hazards model revealed that PD-L1 0% (vs. ≥1%) was an independent factor for longer PFS (adjusted hazard ratio 0.322, 95% confidence interval 0.160-0.650, p = .002). Multiplex IHC in three cases showed a varied extent of immune cell infiltrations in tumors with different PD-L1 expression.CONCLUSIONPositive PD-L1 expression was associated with unfavorable clinical outcomes in patients with ALK-positive lung ADC receiving crizotinib.IMPLICATIONS FOR PRACTICENot all lung adenocarcinoma with sensitizing driver mutations experienced durable responses to small-molecule tyrosine kinase inhibitors (TKIs). Similar to the negative impact of programmed death-ligand 1 (PD-L1) in epidermal growth factor receptor mutant tumors treated with TKIs, this study demonstrated that positive PD-L1 expression was also associated with worse response rate and shorter progression-free survival of anaplastic lymphoma kinase (ALK)-positive adenocarcinoma treated with crizotinib. Among different ALK fusion partners, tumors with short variants (V3 and V5) had higher PD-L1 compared with long variants (V1, V2, and V6). Testing PD-L1 before initiating crizotinib for ALK-positive lung cancer could be a simple method to provide important prognostic information.

Introduction: Besides being a predictive biomarker of response to immunotherapy in lung cancer in general, programmed death-ligand 1 (PD-L1) is not so well correlated with treatment outcomes of lung adenocarcinoma (ADC) harbouring epidermal growth factor receptor (EGFR) mutations, as reported studies are inconclusive and seldom addressed the issues of response to treatment and resistance. The primary objective is to evaluate the association of PD-L1 and EGFR tyrosine kinase inhibitor (TKI) efficacy, resistance, and relevant clinical outcomes. The secondary objective is to further explore the tumour microenvironments of EGFR mutant tumours with different PD-L1 expression. Methods and materials: Using immunohistochemical (IHC) staining, we retrospectively tested PD-L1 expression (Dako 22C3) in the pre-treatment tumours from advanced EGFR mutant lung ADC patients, of whom all were treated with TKIs. Multiplex IHC assay was applied for exploring immune cells in tumour microenvironments. Results: A total of 153 Taiwanese patients were enrolled in our study, of whom a majority of cases were female (58.9%) and non-smokers (75.8%). The objective response rate (ORR) to EGFR TKI and progression-free survival (PFS) were better in patients with PD-L1 expression <50% (ORR/PFS in PD-L1 0% versus 1-49% versus >= 50%: 65.6%/12.5 months versus 56.4%/ 12.8 months versus 38.9%/5.9 months, P < 0.05). The multivariate analysis showed that PDL1 < 50% was an independent prognostic factor for longer PFS (hazard ratio (HR) 0.433, 95% confidence interval (CI) 0.250-0.751, P = 0.003). Furthermore, tumours with higher PD-L1 expression were less likely to develop a secondary T790M mutation (T790M+ in PD-L1 0% versus 1e49% versus similar to 50%: 53.7% versus 35.7% versus 10%, P = 0.024). Multiplex IHC tests were applied in 15 cases and revealed a potential correlation between PD- L1, immune cells, and EGFR TKI responses. Conclusions: Lower pre-treatment PD-L1 is associated with better ORR, PFS, and higher frequency of T790M resistance in EGFR TKI-treated lung ADC patients. (C) 2019 Elsevier Ltd. All rights reserved.

Clinically, high levels of acrolein (a highly reactive α, β-unsaturated aldehyde) and acrolein adducts are detected in the brain of patients with CNS neurodegenerative diseases, including Alzheimer's disease and spinal cord injury. Our previous study supports this notion by showing acrolein as a neurotoxin in a Parkinsonian animal model. In the present study, the effect of AZD6244 (an ATP non-competitive MEK1/2 inhibitor) on acrolein-induced neuroinflammation was investigated using BV-2 cells and primary cultured microglia. Our immunostaining study showed that lipopolysaccharide (LPS, an inflammation inducer as a positive control) increased co-localized immunoreactivities of phosphorylated ERK and ED-1 (a biomarker of activated microglia) in the treated BV-2 cells. Similar elevation in co-localized immunoreactivities of phosphorylated ERK and ED-1 was detected in the acrolein-treated BV-2 cells. Furthermore, Western blot assay showed increases in phosphorylated ERK in BV-2 cells subjected to LPS (1 μg/mL) or acrolein (30 μM); these increases were blocked by AZD6244 (10 μM). At the same time, AZD6244 attenuated LPS-induced TNF-α (a pro-inflammatory cytokine) and cyclooxygenase-II (COX II, a pro-inflammatory enzyme). Consistently, AZD6244 reduced acrolein-induced elevations in COX-II mRNA and COX-II protein expression. In addition, AZD6244 inhibited acrolein-induced increases in activated caspase 1 (a biomarker of inflammasome activation) and heme oxygenase-1 (a redox-regulated chaperone protein) in BV-2 cells. Using a transwell migration assay, AZD6244 attenuated acrolein (5 μM)-induced migration of BV-2 cells and primary cultured microglia. In conclusion, our study shows that acrolein is capable of inducing neuroinflammation which involved ERK activation in microglia. Furthermore, AZD6244 is capable of inhibiting acrolein-induced neuroinflammation. Our study suggests that ERK inhibition may be a neuroprotective target against acrolein-induced neuroinflammation in the CNS neurodegenerative diseases.

Osimertinib is current recommended treatment for EGFR T790M-positive NSCLC following progression on prior EGFR tyrosine kinase inhibitor therapy. However, acquired resistance to osimertinib therapy inevitably developed after a period of effective treatment. We had a patient of EGFR L858R/T790M-positive NSCLC who initially responded to osimertinib therapy but eventually developed resistance. Plasma cell-free DNA analysis disclosed exon-16-skipping HER2 (HER2Δ16) in one osimertinib treated patient. HER2Δ16 was regarded as an oncogenic driver in breast cancer and has never been reported in lung cancer before. Therefore, it’s intriguing to investigate the role of HER2Δ16 in osimertinib resistance in NSCLC. The purpose of this study is to explore the mechanism of HER2Δ16-mediated resistance to osimertinib and to explore strategies to overcome the resistance. We constructed and established H1975 cells stably expressing either vehicle, WT-HER2 or HER2Δ16. We observed that without osimertinib treatment, there was no difference in cell growth and the response to EGF-stimulation. However, when treated with osimertinib, H1975-HER2Δ16 cells were more resistant under normal and EGF-stimulating conditions compared to vehicle or WT-HER2 expressing cells. Moreover, osimertinib treatment in H1975-HER2Δ16 cells had less inhibitory effect on phosphor-ERK and phosphor-AKT compared to vehicle or H1975-WT-HER2 cells. Interestingly, co-treatment of osimertinib with Src-kinase inhibitor, dasatinib, failed to reverse the resistance, indicating that HER2Δ16-driven osimertinib-resistance was independent of Src-kinase. Finally, we revealed that combination of osimertinib with the HER2 small molecular inhibitor, afatinib, can suppress cell growth in H1975-WT-HER2 and H1975-HER2Δ16 cells. In summary, we have shown that HER2Δ16, may be a resistance mechanism to osimertinib in EGFR mutated NSCLC and that HER2Δ16-driven resistance was Src-kinase independent. Moreover, we found the HER2Δ16-driven resistance could be rescued by combination of osimertinib with afatinib. Citation Format: Chia-Chi Hsu, Bin-Chi Liao, Wei-Yu Liao, Aleksandra Markovets, Daniel Stetson, Kenneth Thress, Chih-Hsin Yang. Exon-16-skipping HER2 contributes to osimertinib-resistance through Src-independent manner in EGFRL858R/T790M-positive non-small-cell lung cancer [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 4752.

Introduction: Osimertinib is the current recommended treatment for EGFR T790M-positive NSCLC after EGFR tyrosine kinase inhibitor therapy. However, resistance to osimertinib therapy is inevitably acquired after a period of effective treatment. We had a patient with EGFR L858R/T790M-positive NSCLC who initially responded to osimertinib therapy but eventually experienced development of resistance. Plasma cell-free DNA analysis revealed the occurrence of exon 16-skipping HER2, which may have resulted in the erb-b2 receptor tyrosine kinase 2 gene (HER2) splice variant HER2D16. HER2D16 has never been reported in lung cancer, and HER2D16-driven signaling is known to be regulated by Src kinase in breast cancer. We investigated the role of HER2D16 as an osimertinib-resistant mechanism. Methods: We constructed and established H1975 cells stably expressing HER2D16. The dimeric formation of HER2D16 was tested by using nonreducing polyacrylamide gel electrophoresis. The effects of the study drugs on signaling transduction were examined by using Western blot. Synergistic effect was assessed by using the Chou-Talalay method. Results: We found that HER2D16 can form a homodimer in NSCLC cells. HER2D16-expressing H1975 cells were resistant to osimertinib treatment. We also found that mutant EGFR and HER2D16 cooperated to activate downstream signaling for osimertinib resistance. In addition, cotreatment with osimertinib and an Src kinase inhibitor failed to reverse resistance, indicating that HER2D16-driven signaling in NSCLC did not occur through a canonical pathway. Finally, we revealed that the combination of osimertinib with the pan-HER small-molecule inhibitor afatinib could synergistically repress cell growth and signaling in H1975-HER2D16 cells. Conclusion: HER2D16 can contribute to osimertinib resistance through an Src-independent pathway. HER2D16 should be included in the molecular diagnosis panel for lung cancer. (C) 2019 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

Endoplasmic reticulum (ER) stress is an adaptive response to various stress conditions and plays emerging roles in cancer. Activating transcription factor 6 (ATF6), one of the three major ER stress transducers, has been shown to contribute to chemoresistance by altering cancer cell survival. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncogene, and its expression has been correlated with the prognosis of patients with cancer. In this study, we aimed to explore the relationship between ER stress-related ATF signaling and CIP2A. We found that CIP2A expression was positively correlated with ATF6 expression by analyzing publicly available RNA sequence data of patients with colorectal cancer (The Cancer Genome Atlas, TCGA). In addition, we demonstrated that tunicamycin-induced ER stress invitro upregulated ATF6 and CIP2A. Mechanistically, we found that ATF6 directly bound to the CIP2A promoter and induced CIP2A gene expression, which contributed to colon cancer cell survival. Furthermore, knockdown of CIP2A reduced the viability of cells under ER stress. Most importantly, immunohistochemical analysis of a tissue microarray from a colon cancer patient cohort showed that higher expression levels of ATF6 and CIP2A were associated with a trend toward poor prognosis. Taken together, our results show that ER stress-related ATF6 upregulates CIP2A and contributes to the prognosis of colon cancer. Targeting CIP2A may disrupt ER stress-mediated colon cancer cell survival and thus improve the prognosis of patients with colon cancer.

Deregulated cellular energetics was one of the cancer hallmarks. Several underlying mechanisms of deregulated cellular energetics are associated with mitochondrial dysfunction caused by mitochondrial DNA mutations, mitochondrial enzyme defects, or altered oncogenes/tumor suppressors. In this review, we summarize the current understanding about the role of mitochondrial dysfunction in cancer progression. Point mutations and copy number changes are the two most common mitochondrial DNA alterations in cancers, and mitochondrial dysfunction induced by chemical depletion of mitochondrial DNA or impairment of mitochondrial respiratory chain in cancer cells promotes cancer progression to a chemoresistance or invasive phenotype. Moreover, defects in mitochondrial enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, are associated with both familial and sporadic forms of cancer. Deregulated mitochondrial deacetylase sirtuin 3 might modulate cancer progression by regulating cellular metabolism and oxidative stress. These mitochondrial defects during oncogenesis and tumor progression activate cytosolic signaling pathways that ultimately alter nuclear gene expression, a process called retrograde signaling. Changes in the intracellular level of reactive oxygen species, Ca(2+), or oncometabolites are important in the mitochondrial retrograde signaling for neoplastic transformation and cancer progression. In addition, altered oncogenes/tumor suppressors including hypoxia-inducible factor 1 and tumor suppressor p53 regulate mitochondrial respiration and cellular metabolism by modulating the expression of their target genes. We thus suggest that mitochondrial dysfunction plays a critical role in cancer progression and that targeting mitochondrial alterations and mitochondrial retrograde signaling might be a promising strategy for the development of selective anticancer therapy.

We tested the efficacy of lapatinib, a dual tyrosine kinase inhibitor which interrupts the HER2 and epidermal growth factor receptor (EGFR) pathways, in a panel of triple-negative breast cancer (TNBC) cells, and examined the drug mechanism. Lapatinib showed an anti-proliferative effect in HCC 1937, MDA-MB-468, and MDA-MB-231 cell lines. Lapatinib induced significant apoptosis and inhibited CIP2A and p-Akt in a dose and time-dependent manner in the three TNBC cell lines. Overexpression of CIP2A reduced lapatinib-induced apoptosis in MDA-MB-468 cells. In addition, lapatinib increased PP2A activity (in relation to CIP2A inhibition). Moreover, lapatinib-induced apoptosis and p-Akt downregulation was attenuated by PP2A antagonist okadaic acid. Furthermore, lapatinib indirectly decreased CIP2A transcription by disturbing the binding of Elk1 to the CIP2A promoter. Importantly, lapatinib showed anti-tumor activity in mice bearing MDA-MB-468 xenograft tumors, and suppressed CIP2A as well as p-Akt in these xenografted tumors. In summary, inhibition of CIP2A determines the effects of lapatinib-induced apoptosis in TNBC cells. In addition to being a dual tyrosine kinase inhibitor of HER2 and EGFR, lapatinib also inhibits CIP2A/PP2A/p-Akt signaling in TNBC cells.

Human hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide particularly in Asia. Deregulation of cellular energetics was recently included as one of the cancer hallmarks. Compounds that target the mitochondria in cancer cells were proposed to have therapeutic potential. Biguanide drugs which inhibit mitochondrial complex I and repress mTOR signaling are clinically used to treat type 2 diabetes mellitus patients (T2DM) and were recently found to reduce the risk of HCC in T2DM patients. However, whether alteration of energy metabolism is involved in regulating the sensitivity of HCC to biguanide drugs is still unclear. In the present study, we treated four HCC cell lines with mitochondrial inhibitors (rotenone and oligomycin) and biguanide drugs (metformin and phenformin), and found that the HCC cells which had a higher mitochondrial respiration rate were more sensitive to these treatments; whereas the HCC cells which exhibited higher glycolysis were more resistant. When glucose was replaced by galactose in the medium, the altered energy metabolism from glycolysis to mitochondrial respiration in the HCC cells enhanced the cellular sensitivity to mitochondrial inhibitors and biguanides. The energy metabolism change enhanced AMP-activated protein kinase (AMPK) activation, mTOR repression and downregulation of cyclin D1 and Mcl-1 in response to the mitochondrial inhibitors and biguanides. In conclusion, our results suggest that increased mitochondrial oxidative metabolism upregulates the sensitivity of HCC to biguanide drugs. Enhancing the mitochondrial oxidative metabolism in combination with biguanide drugs may be a therapeutic strategy for HCC.

BACKGROUND:The peroxisome is a single membrane-bound organelle in eukaryotic cells involved in lipid metabolism, including β-oxidation of fatty acids. The human genetic disorder X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene (encoding ALDP, a peroxisomal half ATP-binding cassette [ABC] transporter). This disease is characterized by defective peroxisomal β-oxidation and a large accumulation of very long-chain fatty acids in brain white matter, adrenal cortex, and testis. ALDP forms a homodimer proposed to be the functional transporter, whereas the peroxisomal transporter in yeast is a heterodimer comprising two half ABC transporters, Pxa1p and Pxa2p, both orthologs of human ALDP. While the carboxyl-terminal domain of ALDP is engaged in dimerization, it remains unknown whether the same region is involved in the interaction between Pxa1p and Pxa2p.METHODS/PRINCIPAL FINDINGS:Using a yeast two-hybrid assay, we found that the carboxyl-terminal region (CT) of Pxa2p, but not of Pxa1p, is required for their interaction. Further analysis indicated that the central part of the CT (designated CT2) of Pxa2p was indispensable for its interaction with the carboxyl terminally truncated Pxa1_NBD. An interaction between the CT of Pxa2p and Pxa1_NBD was not detected, but could be identified in the presence of Pxa2_NBD-CT1. A single mutation of two conserved residues (aligned with X-ALD-associated mutations at the same positions in ALDP) in the CT2 of the Pxa2_NBD-CT protein impaired its interaction with Pxa1_NBD or Pxa1_NBD-CT, resulting in a mutant protein that exhibited a proteinase K digestion profile different from that of the wild-type protein. Functional analysis of these mutant proteins on oleate plates indicated that they were defective in transporter function.CONCLUSIONS/SIGNIFICANCE:The CT of Pxa2p is involved in its interaction with Pxa1p and in transporter function. This concept may be applied to human ALDP studies, helping to establish the pathological mechanism for CT-related X-ALD disease.

Abstract Background: Triple-negative breast cancer (TNBC) is a subtype with aggressive behaviors and poor prognosis. Our previous study has shown that CIP2A, cancerous inhibitor of PP2A, may be a novel target in breast cancer cells (Breast Cancer Research 2012). Here, we tested efficacy of lapatinib, a dual tyrosine kinase inhibitor which interrupts the HER2/neu and epidermal growth factor receptor (EGFR) pathways, in a panel of TNBC cell lines and examined the drug mechanism. Methods: TNBC cell lines (HCC-1937, MDA-MB-468, MDA-MB-231) were used for in vitro studies. Apoptosis was examined by both flow cytometry and Western blot. Signal transduction pathways in cells were assessed by Western Blot. Quantitative RT-PCR was used for assessing gene transcription. In vivo efficacy of lapatinib was tested in nude mice with breast cancer xenografts. Results: Lapatinib showed anti-proliferative effect in HCC 1937, MDA-MB-468, and MDA-MB-231 cell lines. Lapatinib induced significant apoptosis in dose-dependent and time-dependent manners in the three tested TNBC cell lines. Importantly, lapatinib inhibited CIP2A and p-Akt in a dose-dependent manner in all sensitive TNBC cells. Overexpression of CIP2A protected MDA-MB-468 cells from lapatinib-induced apoptosis. In addition, lapatinib increased PP2A activity (in relation to CIP2A inhibition) in sensitive cells. Moreover, lapatinib-induced apoptosis as well as lapatinib-induced p-Akt downregulation, was attenuated by PP2A antagonist okadaic acid in sensitive cells. Lapatinib downregulated CIP2A mRNA. Importantly, lapatinib showed anti-tumor activity in mice bearing MDA-MB-468 xenograft tumors, and downregulated CIP2A as well as p-Akt in these xenografted tumors. Conclusions: Inhibition of CIP2A determines the effects of lapatinib-induced apoptosis in TNBC cells. Our data suggest that in addition to a dual tyrosine kinase inhibitor of HER2/neu and EGFR, lapatinib can be a novel CIP2A inhibitor and that CIP2A can be a potential target for TNBC. (Supported by Yen Tjing Ling Medical Foundation; NSC 101-2325-B-075-006, NSC-102-2325-B-075-006 and NSC 100-2325-B-010-007; and V100-D-005-4) Citation Format: Ling-Min Tseng, Chun-Yu Liu, Chia-Jung Hsu, Duen-Shian Wang, Jung-Chen Su, Chung-Wai Shiau, Kuen-Feng Chen. Lapatinib inhibits CIP2A/PP2A/p-Akt signaling and induces apoptosis in triple negative breast cancer cells. [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 2778. doi:10.1158/1538-7445.AM2014-2778

Background SIRT3—mitochondrial nicotinamide adenine dinucleotide-dependent deacetylase sirtuin-3—plays an important role in regulating cell metabolism and carcinogenesis. The role of SIRT3 in gastric cancer has not yet been investigated. Methods A total of 221 gastric cancer patients who underwent curative surgery were enrolled at the Department of Surgery, Taipei Veterans General Hospital. SIRT3 expression in gastric tissues and tumors were examined in these patients using immunohistochemical staining. Clinicopathologic characteristics and survival were analyzed and compared in gastric cancer patients with or without SIRT3 expression. Results The 5-year survival rates of patients with or without SIRT3 expression were 51.2 and 39.1 %, respectively ( p = 0.005). The 5-year disease-free survival rates of patients with or without SIRT3 expression were 49.6 and 38.0 %, respectively ( p = 0.010). Microscopic features showed that there are more poor cell differentiation ( p = 0.001), more diffuse-type Lauren’s histology ( p = 0.018), and more scirrhous-type stromal reactions ( p = 0.027) in gastric cancer without SIRT expression. Multivariate analysis with overall survival as an endpoint showed that age ( p < 0.001), Lauren’s histology ( p = 0.007), stromal reaction ( p = 0.035), TNM pathologic N category ( p < 0.001), and SIRT3 expression ( p < 0.001) were significantly correlated with gastric cancer. Conclusions Gastric cancer patients with SIRT3 expression have a better prognosis than those without. SIRT3 expression is an independent prognostic marker for overall survival and may act as a tumor suppressor in gastric cancer.