Tumor- and circulating-free DNA methylation identifies clinically relevant small cell lung cancer subtypes.

Small cell lung cancer (SCLC) is an aggressive malignancy composed of distinct transcriptional subtypes, but implementing subtyping in the clinic has remained challenging, particularly due to limited tissue availability. Given the known epigenetic regulation of critical SCLC transcriptional programs, we hypothesized that subtype-specific patterns of DNA methylation could be detected in tumor or blood from SCLC patients. Using genomic-wide reduced-representation bisulfite sequencing (RRBS) in two cohorts totaling 179 SCLC patients and using machine learning approaches, we report a highly accurate DNA methylation-based classifier (SCLC-DMC) that can distinguish SCLC subtypes. We further adjust the classifier for circulating-free DNA (cfDNA) to subtype SCLC from plasma. Using the cfDNA classifier (cfDMC), we demonstrate that SCLC phenotypes can evolve during disease progression, highlighting the need for longitudinal tracking of SCLC during clinical treatment. These data establish that tumor and cfDNA methylation can be used to identify SCLC subtypes and might guide precision SCLC therapy.

Targeting BCL2 Overcomes Resistance and Augments Response to Aurora Kinase B Inhibition by AZD2811 in Small Cell Lung Cancer.

PURPOSE: Therapeutic resistance to frontline therapy develops rapidly in small cell lung cancer (SCLC). Treatment options are also limited by the lack of targetable driver mutations. Therefore, there is an unmet need for developing better therapeutic strategies and biomarkers of response. Aurora kinase B (AURKB) inhibition exploits an inherent genomic vulnerability in SCLC and is a promising therapeutic approach. Here, we identify biomarkers of response and develop rational combinations with AURKB inhibition to improve treatment efficacy. EXPERIMENTAL DESIGN: Selective AURKB inhibitor AZD2811 was profiled in a large panel of SCLC cell lines (n = 57) and patient-derived xenograft (PDX) models. Proteomic and transcriptomic profiles were analyzed to identify candidate biomarkers of response and resistance. Effects on polyploidy, DNA damage, and apoptosis were measured by flow cytometry and Western blotting. Rational drug combinations were validated in SCLC cell lines and PDX models. RESULTS: AZD2811 showed potent growth inhibitory activity in a subset of SCLC, often characterized by, but not limited to, high cMYC expression. Importantly, high BCL2 expression predicted resistance to AURKB inhibitor response in SCLC, independent of cMYC status. AZD2811-induced DNA damage and apoptosis were suppressed by high BCL2 levels, while combining AZD2811 with a BCL2 inhibitor significantly sensitized resistant models. In vivo, sustained tumor growth reduction and regression was achieved even with intermittent dosing of AZD2811 and venetoclax, an FDA-approved BCL2 inhibitor. CONCLUSIONS: BCL2 inhibition overcomes intrinsic resistance and enhances sensitivity to AURKB inhibition in SCLC preclinical models.

Methylation of Tumor Suppressive miRNAs in Plasma from Patients With Pancreaticobiliary Diseases.

BACKGROUND/AIM: We previously reported the usefulness of aberrant methylation of tumor suppressive miRNAs in bile to discriminate pancreaticobiliary cancers (PBCs) from benign pancreaticobiliary diseases (BD). Here we performed a methylation analysis of plasma miRNAs to identify miRNAs specific for PBCs. PATIENTS AND METHODS: Plasma was collected from 80 patients with pancreatic cancer (PC); 18 with biliary tract cancer (BTC) and 28 with BD. Sequences encoding 3 tumor suppressive miRNAs (miR-200a, -200b, and -1247) were PCR amplified and sequenced, and their methylation rates were determined. RESULTS: The methylation rate of miR-1247 was significantly higher in patients with BTC than in those with BD, and tended to be higher in patients with PC than in those with BD. Furthermore, it was significantly higher in three patients with stages I/II BTC than in those with BD. CONCLUSION: Methylation of miR-1247 in plasma may be useful to distinguish BTC from BD.

Inhibition of EGFR and MEK surmounts entrectinib resistance in a brain metastasis model of NTRK1-rearranged tumor cells.

Tropomyosin receptor kinase (TRK) inhibitors have demonstrated histology-agnostic efficacy in patients with neurotrophic receptor tyrosine kinase (NTRK) gene fusion. Although responses to TRK inhibitors can be dramatic and durable, duration of response may eventually be limited by acquired resistance via several mechanisms, including resistance mutations such as NTRK1-G595R. Repotrectinib is a second-generation TRK inhibitor, which is active against NTRK1-G595R. However, its efficacy against entrectinib-resistant tumors has not been fully elucidated. In the present study, we established entrectinib-resistant tumor cells (M3B) in a brain metastasis model inoculated with NTRK1-rearranged KM12SM cells and examined the sensitivity of M3B cells to repotrectinib. While M3B cells harbored the NTRK1-G595R mutation, they were unexpectedly resistant to repotrectinib. The resistance was due to extracellular signal-regulated kinase (ERK) reactivation partially mediated by epidermal growth factor receptor (EGFR) activation. We further demonstrate that the triplet combination of repotrectinib, EGFR inhibitor, and MEK inhibitor could sensitize M3B cells in vitro as well as in a brain metastasis model. These results indicate that resistant mutations, such as NTRK1-G595R, and alternative pathway activation, such as ERK activation, could simultaneously occur in entrectinib-resistant tumors, thereby causing resistance to second-generation inhibitor repotrectinib. These findings highlight the importance of intensive examinations to identify resistance mechanisms and application of the appropriate combination treatment to circumvent the resistance.

Clinical efficacy of dacomitinib in rechallenge setting for patients with epidermal growth factor receptor mutant non-small cell lung cancer: A multicenter retrospective analysis (TOPGAN2020-02).

BACKGROUND: Dacomitinib is the second-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) for mutant non-small cell lung cancer (NSCLC). EGFR-TKIs are often re-administered in Japan after the disease progression prior EGFR-TKI. There is little evidence of dacomitinib in rechallenge setting. This study evaluated clinical outcomes of dacomitinib in rechallenge setting. METHODS: Patients who received dacomitinib for advanced EGFR-mutant NSCLC who had progressed after EGFR-TKI in nine institutions in Japan were included in the analyses. RESULTS: In total, 43 patients were analyzed. The median progression-free survival (PFS) was 4.3 months (95% confidence interval [CI], 2.5-5.6). The overall survival (OS) was 10.5 months (95% CI, 7.4-not reached). The overall response rate was 25.5% (95% CI, 13.1-33.7). Subset analysis indicated that patients with EGFR exon 21 L858R showed longer PFS than those with EGFR exon 19 deletion (5.8 vs. 4.1 months) (p = 0.018). The most common adverse events leading to dose modification were diarrhea, paronychia, rash, and oral mucositis. CONCLUSION: In the real practice in Japan, dacomitinib showed a worthwhile treatment option for NSCLC patients with EGFR mutation after failure of previous EGFR-TKI. The benefit was especially pronounced in patients with the exon 21 mutation.

STAT3 inhibition suppresses adaptive survival of ALK-rearranged lung cancer cells through transcriptional modulation of apoptosis.

Patients with advanced anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer who are prescribed ALK-tyrosine kinase inhibitors (ALK-TKIs) rarely have complete responses, with residual tumors relapsing as heterogeneous resistant phenotypes. Herein, we investigated new therapeutic strategies to reduce and eliminate residual tumors in the early treatment phase. Functional genomic screening using small guide RNA libraries showed that treatment-induced adaptive survival of ALK-rearranged lung cancer cells was predominantly dependent on STAT3 activity upon ALK inhibition. STAT3 inhibition effectively suppressed the adaptive survival of ALK-rearranged lung cancer cells by enhancing ALK inhibition-induced apoptosis. The combined effects were characterized by treatment-induced STAT3 dependence and transcriptional regulation of anti-apoptotic factor BCL-XL. In xenograft study, the combination of YHO-1701 (STAT3 inhibitor) and alectinib significantly suppressed tumor regrowth after treatment cessation with near tumor remission compared with alectinib alone. Hence, this study provides new insights into combined therapeutic strategies for patients with ALK-rearranged lung cancer.

Multi-institutional survey of thymic carcinoma patients in Hokushin region.

BACKGROUND: Thymic carcinoma is a rare neoplasm, and its prognosis is very poor. The purpose of this study was to validate the clinical and epidemiological factors, diagnosis and initial treatment of thymic carcinoma among all patients diagnosed in the registered hospital group. METHODS: We surveyed retrospective data from 152,921 cancer patients in 22 principal hospitals. RESULTS: A total of 88 thymic carcinoma cases were newly diagnosed. These patients were 50 men and 38 women, with a median age of 66 years old. Eight patients were discovered in cancer screening, 9 in a voluntary setting, 14 at health checkups, 25 at follow-up of other diseases, and 32 cases by introduction from another hospital. Only 14 cases had been diagnosed with localized disease, but 5 cases were accompanied by regional lymph node metastasis. Furthermore, 12 cases showed infiltration into adjacent organs, and 24 cases had distant metastasis. Eighty-three cases were diagnosed by a pathological diagnosis. A surgical approach, chemotherapy, and radiotherapy were performed for 29, 35 patients, and 31 patients, respectively, while 17 patients received best supportive care. CONCLUSION: The diagnosis of thymic carcinoma is still difficult, and this disease has a tragically rapid progression if when discovered during follow-up of other diseases. An innovative modality for the early detection of thymic carcinoma is needed in modern medical society.

Mediastinal Malignant Melanoma Markedly Shrinking in Response to Nivolumab.

Primary malignant melanoma (MM) of the mediastinum is rare, and there is a lack of consensus regarding the preferred treatment because non-cutaneous MM demonstrates an inferior response to systemic therapy. Herein, we describe the case of a 73-year-old man with MM of the anterior mediastinum with multiple liver metastases. Even though the size of lesions increased rapidly following diagnosis, nivolumab monotherapy caused remarkable tumor shrinkage. This is the first report of mediastinal MM showing a significant response to nivolumab. We, therefore, suggest that immunotherapy may be one of the treatment options for primary mediastinal MM.

Multi-institutional survey of malignant pleural mesothelioma patients in the Hokushin region.

BACKGROUND: Malignant pleural mesothelioma (MPM) is a major occupational and environmental neoplasm. The purpose of this study was to validate the clinical and epidemiological factors, diagnosis, and initial treatment among MPM patients in the Hokushin region. METHODS: We surveyed retrospective data from 152,921 cancer patients in 22 principal hospitals. RESULTS: A total of 166 MPM cases were newly diagnosed. These patients consisted of 136 men and 30 women, with a median age of 69 years. We estimated the incidence rate for MPM to be 0.55 cases per 100,000 person-years in this study. The ratio per 100,000 population-years was 0.39 in Fukui, 0.60 in Ishikawa, 1.02 in Toyama and 0.35 in Nagano. Forty-five patients were discovered when diagnosed incidentally in patients under observations for other diseases. Forty-six cases were diagnosed as localized disease, while 13 had accompanying regional lymph node metastasis. Furthermore, 44 cases showed infiltration into adjacent organs. A histo-cytological diagnosis was made in 164 cases (98.8%). A surgical approach, chemotherapy, and radiotherapy were performed for 33, 88, and 6 patients, respectively, while 44 patients (26.5%) received best supportive care. Multimodality therapy was conducted in just 3.0% of the MPM patients CONCLUSION: MPM has a tragically rapid progression if discovered under observations for other diseases. Workers in health-related fields should be on high alert for aggressive MPM. Better evaluation and multi-disciplinary approaches to MPM in these regions are needed to optimize multimodality therapy.

Cancer among children, adolescents and young adults in the Hokushin region, Japan, between 2010 and 2015.

Adolescents and young adults with cancer encounter age-related challenges. Cancer treatment and support are not always tailored to the needs of each patient due to difficulty in the collection of accurate data. The present study aimed to investigate cancer among children and adolescents and young adults in the four adjacent prefectures of Japan (Toyama, Ishikawa, Fukui and Nagano) by analyzing data from a unique regional cancer database. We retrieved and analyzed the data of pediatric and adolescent and young adult patients aged between 0 and 39 years at cancer diagnosis (including carcinoma in situ), which was registered in the Hokushin Ganpro database between 2010 and 2015. A total of 5718 cases (1571 males and 4147 females) were identified during this period. The overall male-to-female ratio was 1:2.6. There was no distinct difference in the number of cancer cases per 100 000 population between males and females until 19 years of age. The difference became more pronounced after 20 years of age. The number of cancer cases (per 100 000 population) in the 0-14-, 15-19-, 20-29- and 30-39-year age groups was estimated to be 13.4, 14.5, 44.0 and 101.5, respectively. Carcinomas were the most common type of cancer in the adolescents and young adults (15-39 years) population (74%), whereas they were not the predominant cancer type in the pediatric (0-14 years) population. Although further research is needed to understand the needs of adolescents and young adults with cancer, we believe that our findings will help guide efforts to improve the management strategy for adolescents and young adults with cancer.

Severe Skin Toxicity Caused by Sequential Anti-PD-1 Antibody and Alectinib in Non-small-cell Lung Cancer: A Report of Two Cases and a Literature Review.

Immune checkpoint inhibitors (ICIs) have demonstrated marked efficacy in some cancer patients, but they may cause various severe immune-related adverse events. Alectinib is a second-generation anaplastic lymphoma kinase (ALK)-tyrosine kinase inhibitor (TKI) approved for ALK-rearranged non-small-cell lung cancer (NSCLC). Alectinib is said to be safer than other TKIs. We conducted an investigator-initiated trial of alectinib, which also has RET kinase-inhibitory activity, against RET-rearranged NSCLC. Two RET-rearranged NSCLC patients experienced severe skin toxicity with alectinib after first undergoing anti-PD-1 antibody treatment with an ICI. These findings suggest that we should carefully follow patients for adverse effects of targeted drugs following ICI treatment.

A phase I/II study of osimertinib in EGFR exon 20 insertion mutation-positive non-small cell lung cancer.

OBJECTIVES: Several preclinical data proposed a potential efficacy of osimertinib, a third-generation EGFR tyrosine kinase inhibitor, for EGFR exon 20 insertion (EGFR ex20ins)-positive non-small cell lung cancer (NSCLC). However, reported case series and a retrospective study proposed controversial efficacy. The efficacy of osimertinib in EGFR ex20ins-positive NSCLC have not been well evaluated in prospective clinical trials. In this study, we performed a prospective, single-arm, multi-center, open-label, non-randomized phase I/II study to evaluate efficacy of osimertinib for EGFR ex20ins-positive NSCLC. MATERIALS AND METHODS: From August 2018 to January 2020, 14 NSCLC patients with EGFR ex20ins were enrolled, of whom 2 were excluded because they did not meet the inclusion criteria. Efficacy and safety of 80 mg osimertinib were evaluated. In addition, we performed a translational exploratory study to clarify the association of mutation type-specific drug sensitivity, osimertinib pharmacokinetic data, and clinical efficacy. RESULTS: Of the evaluated patients, none experienced objective response, 7 experienced stable disease (58.3%), and 5 experienced disease progression (41.7%). The median progression free survival (PFS) was 3.8 months, and the median overall survival was 15.8 months. Interestingly, the exploratory study demonstrated statistically significant positive correlation between plasma osimertinib concentration/in vitro IC50 ratio and PFS (R = 0.9912, P = 0.0001), highlighting the mutation type-specific concentration-dependent efficacy of osimertinib for EGFR ex20ins-positive NSCLC. CONCLUSIONS: Regular dose, 80 mg/day, of osimertinib has limited clinical activity in NSCLC patients with EGFR ex20ins. The translational study proposed the potential efficacy of higher dose osimertinib in a subgroup of EGFR ex20ins-positive NSCLC.

Trametinib overcomes KRAS-G12V-induced osimertinib resistance in a leptomeningeal carcinomatosis model of EGFR-mutant lung cancer.

Leptomeningeal carcinomatosis (LMC) occurs frequently in non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations and is associated with acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). However, the mechanism by which LMC acquires resistance to osimertinib, a third-generation EGFR-TKI, is unclear. In this study, we elucidated the resistance mechanism and searched for a novel therapeutic strategy. We induced osimertinib resistance in a mouse model of LMC using an EGFR-mutant NSCLC cell line (PC9) via continuous oral osimertinib treatment and administration of established resistant cells and examined the resistance mechanism using next-generation sequencing. We detected the Kirsten rat sarcoma (KRAS)-G12V mutation in resistant cells, which retained the EGFR exon 19 deletion. Experiments involving KRAS knockdown in resistant cells and KRAS-G12V overexpression in parental cells revealed the involvement of KRAS-G12V in osimertinib resistance. Cotreatment with trametinib (a MEK inhibitor) and osimertinib resensitized the cells to osimertinib. Furthermore, in the mouse model of LMC with resistant cells, combined osimertinib and trametinib treatment successfully controlled LMC progression. These findings suggest a potential novel therapy against KRAS-G12V-harboring osimertinib-resistant LMC in EGFR-mutant NSCLC.

Multi-institutional survey of cancer disparities in disabled patients in the region of northwestern Japan.

BACKGROUND: Potential disparities between cancer patients with and without disabilities remained to be validate in Japan. METHODS: We surveyed retrospective data on hospital cancer registration as well as information on disability certificates obtained through the Hokushin Ganpro database. In total, 93,545 cancer patients in 10 principal hospitals covering the region of northwestern Japan were registered with the Hokushin Ganpro database between 2010 and 2015. The database included the following data: diagnosis date, cancer type, staging, treatment, cancer detection process, and possession of a disability certificate. RESULTS: We found that 2983 patients, which accounted for 3.2% of the total patients, had disabilities. No significant differences in gender, age at diagnosis, cancer stage distribution, and cancer incidence rates were observed between the disabled and non-disabled patients. Even though the proportion of early-stage cancer among disabled patients differed only slightly from that in non-disabled patients, early-stage cancer was more frequently diagnosed in patients with disabilities during their regular hospital visits than in those without disabilities, who had more opportunity for early cancer detection during cancer screening. According to in-house data reflecting treatment period and process from a single hospital, all 16 disabled patients treated with chemotherapy completed the treatment until disease progression or end of predetermined cycles. CONCLUSION: These results indicate that deep disparities between cancer patients with and without disabilities are not apparent and that the disabled patients in the region of northwestern Japan receive appropriate hospital follow-up.

Phase 1/2 study of alectinib in RET-rearranged previously-treated non-small cell lung cancer (ALL-RET).

BACKGROUND: Rearranged during transfection (RET) rearrangements occur in 1-2% of non-small cell lung cancers (NSCLCs). Alectinib administered at doses of 300 mg and 600 mg twice daily (BID) is approved for. ALK: rearranged NSCLC in Japan and other countries, respectively. Since alectinib has activity against RET, we conducted a phase (P) 1/2 study of alectinib to determine its activity in Japanese patients with. RET: rearranged NSCLC. METHODS: This study was a single-arm, open-label, multi-institutional P1/2 trial. Previously treated patients with RET-rearranged NSCLC, screened by nation-wide network (LC-SCRUM-Japan), were recruited. In P1, alectinib (600 or 450 mg BID) was administered following a 3+3 design and its safety was assessed. During P2, alectinib was administered at the recommended dose (RD) determined in P1. The primary endpoint was the objective response rate (ORR) in RET inhibitor-naïve patients treated with the RD of alectinib. RESULTS: Thirty-four patients were administered alectinib. In cohort 1 (600 mg BID) of P1, we observed 5 dose-limiting toxicities (DLTs), including grade 3 rash and thromboembolic event, in 3 of 6 patients. In cohort 2 (450 mg BID), we observed no DLTs in 3 patients. Pharmacokinetic analysis revealed that AUC0-10 to 600 mg BID was higher than that previously reported in global trials. We determined 450 mg BID as the RD for P2. In 25 RET inhibitor-naïve patients, one achieved an objective response (4%) and 13 achieved disease control at 8 weeks (52%). The median progression-free survival (PFS) was 3.4 months (95% CI, 2.0-5.4), while the median overall survival was 19.0 months (5.4-NE). We observed grade 3 adverse events (AEs) (4%) including pneumonitis in P2. CONCLUSIONS: Alectinib exerts limited activity against RET-rearranged NSCLC. Further investigation to elucidate the mechanisms underlying sensitivity and resistance of RET inhibitors is required to improve outcomes for these patients.

Sarcopenia may Influence the Prognosis in Advanced Thyroid Cancer Patients Treated With Molecular Targeted Therapy.

BACKGROUND/AIM: Reportedly, sarcopenia and nutritional status are associated with prognosis in cancer patients. However, data regarding the relationship of these factors with advanced thyroid cancer patients receiving molecular targeted therapy remains scarce. Therefore, we investigated the relationship between nutritional assessment, as well as sarcopenia, and prognosis in patients with advanced thyroid cancer undergoing molecular targeted therapy. PATIENTS AND METHODS: In this retrospective study, sarcopenia and several markers of nutritional status were assessed in advanced thyroid cancer patients at the Kanazawa University Hospital, before the introduction of molecular targeted therapy. RESULTS: Advanced thyroid cancer patients with sarcopenia presented a worse prognosis than those without sarcopenia. Additionally, sarcopenia strongly correlated with several markers of nutritional status, such as albumin, prognostic nutrition index, and Glasgow prognostic score. CONCLUSION: Sarcopenia could be a prognostic factor in patients with advanced thyroid cancer receiving molecular targeted therapy.

Proteasome Inhibition Overcomes ALK-TKI Resistance in ALK-Rearranged/TP53-Mutant NSCLC via Noxa Expression.

PURPOSE: In ALK-rearranged non-small cell lung cancer (NSCLC), impacts of concomitant genetic alterations on targeted therapies with ALK-tyrosine kinase inhibitors (ALK-TKI) are not yet well understood. Here, we investigated genetic alterations related to ALK-TKI resistance using clinico-genomic data and explored effective therapies to overcome the resistance in preclinical models through the identification of underlying molecular mechanisms. EXPERIMENTAL DESIGN: We used integrated clinical and next-generation sequencing data generated in a nationwide lung cancer genome screening project (LC-SCRUM-Japan). ALK-rearranged NSCLC cell lines expressing wild-type or mutant TP53 were used to evaluate cellular apoptosis induced by ALK-TKIs. RESULTS: In 90 patients with ALK-rearranged NSCLC who were treated with a selective ALK-TKI, alectinib, TP53 comutated patients showed significantly worse progression-free survival (PFS) than TP53 wild-type patients [median PFS, 11.7 months (95% confidence interval, CI, 6.3-not reached, NR) vs. NR (23.6-NR); P = 0.0008; HR, 0.33 (95% CI, 0.17-0.65)]. ALK-rearranged NSCLC cell lines that lost p53 function were resistant to alectinib-induced apoptosis, but a proteasome inhibitior, ixazomib, markedly induced apoptosis in the alectinib-treated cells by increasing the expression of a proapoptotic protein, Noxa, which bound to an antiapoptotic protein, Mcl-1. In subcutaneous tumor models, combination of ixazomib and alectinib prominently induced tumor regression and apoptosis even though the tumors were generated from ALK-rearranged NSCLC cells with nonfunctional p53. CONCLUSIONS: These clinical and preclinical results indicate concomitant TP53 mutations reduce the efficacy of alectinib for ALK-rearranged NSCLC and the combined use of a proteasome inhibitor with alectinib is a promising therapy for ALK-rearranged/TP53-mutated NSCLC.

Multiple Malignant Lymphomas of the Bile Duct Developing after Spontaneous Regression of an Autoimmune Pancreatitis-like Mass.

We herein report a 67-year-old woman with malignant lymphomas of the bile duct that developed after regression of a pancreatic head mass. Computed tomography suggested the mass was pancreatic head cancer. Endoscopic ultrasonography showed a low-echoic mass with hyperechoic strands resembling autoimmune pancreatitis. Her serum IgG4 concentration was elevated to 674 mg/dL. After the pancreatic head mass spontaneously diminished, three masses were detected in the common bile duct. A biopsy of the major papilla revealed high-grade B-cell lymphoma with MYC, BCL2 and/or BCL6 rearrangement. Systemic chemotherapy with rituximab plus etoposide, prednisolone, vincristine, cyclophosphamide and doxorubicin resulted in complete remission.

Resminostat, a histone deacetylase inhibitor, circumvents tolerance to EGFR inhibitors in EGFR-mutated lung cancer cells with BIM deletion polymorphism.

Drug-tolerant cells are mediators of acquired resistance. BIM-intron2 deletion polymorphism (BIM-del) is one of the mechanisms underlying the resistance to epidermal growth factor tyrosine kinase inhibitor (EGFR-TKI)-mediated apoptosis that induces drug tolerance. Here, we investigated whether resminostat, a histone deacetylase inhibitor, circumvents BIM-del-associated apoptosis resistance. The human EGFR-mutated non-small cell lung cancer (NSCLC) cell line PC-9 and its homozygous BIM-del-positive variant (PC-9 BIMi2- / -), established by editing with zinc finger nuclease, were used. In comparison with PC-9 cells, PC-9 BIMi2- / - cells were less sensitive to apoptosis mediated by EGFR-TKIs such as gefitinib and osimertinib. The combined use of resminostat and an EGFR-TKI preferentially induced the expression of the pro-apoptotic BIM transcript containing exon 4 rather than that containing exon 3, increased the level of pro-apoptotic BIM protein (BIMEL), and stimulated apoptosis in vitro. In a subcutaneous tumor model derived from PC-9 BIMi2- / - cells, gefitinib monotherapy decreased tumor size but retained residual lesions, indicative of the presence of tolerant cells in tumors. The combined use of resminostat and gefitinib increased BIMEL protein level and induced apoptosis, subsequently leading to the remarkable shrinkage of tumor. These findings suggest the potential of resminostat to circumvent tolerance to EGFR-TKIs associated with BIM deletion polymorphism. J. Med. Invest. 67 : 343-350, August, 2020.

Transient IGF-1R inhibition combined with osimertinib eradicates AXL-low expressing EGFR mutated lung cancer.

Drug tolerance is the basis for acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) including osimertinib, through mechanisms that still remain unclear. Here, we show that while AXL-low expressing EGFR mutated lung cancer (EGFRmut-LC) cells are more sensitive to osimertinib than AXL-high expressing EGFRmut-LC cells, a small population emerge osimertinib tolerance. The tolerance is mediated by the increased expression and phosphorylation of insulin-like growth factor-1 receptor (IGF-1R), caused by the induction of its transcription factor FOXA1. IGF-1R maintains association with EGFR and adaptor proteins, including Gab1 and IRS1, in the presence of osimertinib and restores the survival signal. In AXL-low-expressing EGFRmut-LC cell-derived xenograft and patient-derived xenograft models, transient IGF-1R inhibition combined with continuous osimertinib treatment could eradicate tumors and prevent regrowth even after the cessation of osimertinib. These results indicate that optimal inhibition of tolerant signals combined with osimertinib may dramatically improve the outcome of EGFRmut-LC.