A synthetic lethal strategy using PARP and ATM inhibition for overcoming trastuzumab resistance in HER2-positive cancers.

Despite its clinical efficacy in HER2-positive cancers, resistance to trastuzumab inevitably occurs. The DNA damage response (DDR) pathway is essential for maintaining genomic stability and cell survival. However, the role of the DDR pathway in HER2-positive tumors and trastuzumab resistance remains elusive. In this study, we verified that increased PARP1 expression in trastuzumab-resistant (TR) cells, owing to its augmented stability by escape from proteasomal degradation, confers tolerability to trastuzumab-induced DNA damage. Interruption of PARP1 in TR cells restrains its cellular growth, while simultaneously activating ATM to retain its genome stability. Dual inhibition of PARP and ATM induces synthetic lethality in TR cells by favoring the toxic NHEJ pathway instead of the HRR pathway. Our results highlight the potential of clinical development of DDR-targeting strategies for trastuzumab-resistant HER2-positive cancer patients.

Gemcitabine and cisplatin plus durvalumab with or without tremelimumab in chemotherapy-naive patients with advanced biliary tract cancer: an open-label, single-centre, phase 2 study.

BACKGROUND: Immunotherapies have shown clinical activity in patients with advanced biliary tract cancer, for which outcomes remain poor despite standard of care treatment with gemcitabine and cisplatin. We aimed to evaluate gemcitabine and cisplatin plus durvalumab with or without tremelimumab as first-line treatment in patients with advanced biliary tract cancer. METHODS: This open-label, single-centre, phase 2 study was conducted at Seoul National University Hospital. Eligible patients were treatment-naïve adults aged 18 years or older with histologically proven unresectable or recurrent biliary tract cancer, at least one measurable lesion based on the Response Evaluation Criteria in Solid Tumors (version 1.1), an Eastern Cooperative Oncology Group performance status of 0 or 1, life expectancy of 12 weeks or longer, and adequate healthy organ and bone marrow function. Initially, all patients received one 3-week cycle of gemcitabine (1000 mg/m2) and cisplatin (25 mg/m2) on day 1 and 8 followed by gemcitabine and cisplatin plus durvalumab (1120 mg) and tremelimumab (75 mg) on day 1 of each cycle, starting with the second cycle (chemotherapy followed by chemotherapy plus durvalumab and tremelimumab group). Following protocol amendment, patients were recruited to receive gemcitabine and cisplatin plus durvalumab, starting on day 1 of the first cycle (chemotherapy plus durvalumab group) or gemcitabine and cisplatin plus durvalumab and tremelimumab also from day 1 of the first cycle (chemotherapy plus durvalumab and tremelimumab group) in parallel and allocated using a random block method. Assessors and patients were not masked to the treatment group. The primary endpoint was objective response rate, assessed in the efficacy population (ie, patients who were treated at least until the first tumour response assessment). This study is registered with ClinicalTrials.gov, NCT03046862 (active). FINDINGS: Between March 2, 2017, and Feb 13, 2020, 128 patients were enrolled (32 in the chemotherapy followed by chemotherapy plus durvalumab and tremelimumab group, 49 in the chemotherapy plus durvalumab group, and 47 in the chemotherapy plus durvalumab and tremelimumab group). Four patients (two in the chemotherapy followed by chemotherapy plus durvalumab and tremelimumab group and two in the chemotherapy plus durvalumab group) were excluded and 124 were evaluable for tumour response. The median duration of follow-up was 48·2 months (IQR 41·5-49·4) for the chemotherapy followed by chemotherapy plus durvalumab and tremelimumab group, 26·6 months (19·0-27·9) for the chemotherapy plus durvalumab group, and 24·2 months (20·7-31·7) for the chemotherapy plus durvalumab and tremelimumab group. 82 (66%) of 124 patients achieved an objective response (15 [50%] of 30 in the chemotherapy followed by chemotherapy plus durvalumab and tremelimumab group, 34 [72%] of 47 in the chemotherapy plus durvalumab group, and 33 [70%] of 47 in the chemotherapy plus durvalumab and tremelimumab group). The most common grade 3 and 4 adverse events were decreased neutrophil count (67 [53%] of 126), anaemia (50 [40%]), and decreased platelet count (24 [19%]), with no unexpected safety events. No adverse events leading to discontinuation or death occurred. INTERPRETATION: Gemcitabine and cisplatin plus immunotherapy showed promising efficacy and acceptable safety in patients with biliary tract cancer. Gemcitabine and cisplatin plus durvalumab are being evaluated in the phase 3, TOPAZ-1 study (NCT03875235) as first-line treatment in patients with advanced biliary tract cancer. FUNDING: AstraZeneca; National Research Foundation of Korea (Grant No. 2021R1A2C2007430).

Inhibition of WEE1 Potentiates Sensitivity to PARP Inhibitor in Biliary Tract Cancer.

PURPOSE: Up to 20% of patients with biliary tract cancer (BTC) have alterations in DNA damage response (DDR) genes, including homologous recombination (HR) genes. Therefore, the DDR pathway could be a promising target for new drug development in BTC. We aim to investigate the anti-tumor effects using poly(ADP-ribose) polymerase (PARP) and WEE1 inhibitors in BTC. MATERIALS AND METHODS: We used 10 BTC cell lines to evaluate an anti-tumor effect of olaparib (a PARP inhibitor) and AZD1775 (a WEE1 inhibitor) in in vitro. Additionally, we established SNU869 xenograft model for in vivo experiments. RESULTS: In this study, we observed a modest anti-proliferative effect of olaparib. DNA double-strand break (DSB) and apoptosis were increased by olaparib in BTC cells. However, olaparib-induced DNA DSB was repaired through the HR pathway, and G2 arrest was induced to secure the time for repair. As AZD1775 typically regulates the G2/M checkpoint, we combined olaparib with AZD1775 to abrogate G2 arrest. We observed that AZD1775 downregulated p-CDK1, a G2/M cell cycle checkpoint protein, and induced early mitotic entry. AZD1775 also decreased CtIP and RAD51 expression and disrupted HR repair. In xenograft model, olaparib plus AZD1775 treatment reduced tumor growth more potently than did monotherapy with either drug. CONCLUSION: This is the first study to suggest that olaparib combined with AZD1775 can induce synergistic anti-tumor effects against BTC. Combination therapy that blocks dual PARP and WEE1 has the potential to be further clinically developed for BTC patients.

ATR inhibition amplifies antitumor effects of olaparib in biliary tract cancer.

Olaparib, a potent PARP inhibitor, has been shown to have great anti-tumor effects in some tumor types. Although biliary tract cancer (BTC) is a good candidate for DNA damage response (DDR)-targeted agents, targeted DDR inhibitors, including olaparib, are currently rarely evaluated in BTC. In our project, a total of ten BTC cell lines were used to assess the efficacy of olaparib. Olaparib alone showed moderate anti-proliferative effects in BTC cells and increased p-ATR and PD-L1 expression levels. In combination with an ATR inhibitor (AZD6738, ceralasertib) showed synergistic anti-proliferative effects and increased DNA strand breaks in vitro. PD-L1 induced by olaparib was also downregulated by ceralasertib through p-STAT-3 and YAP reduction with or without human primary peripheral blood mononuclear cells. In SNU478-xenograft models, the combination treatment significantly suppressed tumor growth. PD-L1 and YAP were strongly downregulated, similar to in vitro conditions, and expression of CXCR2 and CXCR4 was further reduced. In the current ongoing clinical trial (NCT04298021), BTC patients treated with olaparib and ceralasertib combination have shown tumor response. In conclusion, co-targeting of PARP and ATR might be a potential therapeutic approach for patients with BTC.

WEE1 inhibition reverses trastuzumab resistance in HER2-positive cancers.

BACKGROUND: To date, many efforts have been made to understand the resistance mechanism of trastuzumab in human epidermal growth factor receptor 2 (HER2)-positive breast and gastric cancer. However, there is still a huge unmet medical need for patients with trastuzumab resistance. METHODS: In our study, we generated four trastuzumab-resistant (HR) cancer cell lines from ERBB2-amplified gastric and biliary tract cancer cell lines (SNU-216, NCI-N87, SNU-2670, and SNU-2773). RESULTS: Here, we found higher PD-L1 expression in trastuzumab-resistant (HR) HER2-positive cancer cells than in parental cells, and blocking PD-L1 reversed the resistance to trastuzumab in HR cells. Trastuzumab upregulated PD-L1 expression via NF-κB activation in both parental and HR cells, however, led to DNA damage only in parental cells. The WEE1 inhibitor adavosertib, which downregulates PD-L1 expression, enhanced trastuzumab efficacy by blocking BRCA1-CMTM6-PD-L1 signals and the HER2-CDCP-1-SRC axis. Additionally, the levels of galectin-9, CD163, FoxP3, and CTLA-4 were diminished by blocking WEE1 in the presence of human PBMCs in vitro. CONCLUSION: Taken together, the strategy of co-targeting HER2 and WEE1 could overcome resistance to trastuzumab in HER2-positive cancers, supporting further clinical development in HER2-positive cancer patients.

Prognostic Value of Serum Soluble Programmed Death-Ligand 1 and Dynamics During Chemotherapy in Advanced Gastric Cancer Patients.

PURPOSE: The soluble form programmed death-ligand 1 (sPDL1) has immunosuppressive properties and is being studied as a candidate biomarker for immuno-oncology drug development. We measured the serum sPDL1 at pre-and post-chemotherapy and evaluated its prognostic implication and dynamics during chemotherapy in advanced gastric cancer (GC). MATERIALS AND METHODS: We prospectively enrolled 68 GC patients who were candidates for palliative standard first-line chemotherapy, and serially collected blood at baseline and after one cycle of chemotherapy, at the best response and after disease progression. sPDL1 was measured using an enzyme-linked immunosorbent assay. Response to chemotherapy, overall survival (OS), progressionfree survival (PFS) and other prognostic factors including neutrophil-lymphocyte ratio (NLR) were obtained. The cut-off value of sPDL1 levels for survival analysis was found using C-statistics. RESULTS: The median baseline sPDL1 was 0.8 ng/mL (range, 0.06 to 6.06 ng/mL). The median OS and PFS were 14.9 months and 8.0 months, respectively. sPDL1 and NLR showed a weak positive correlation (Spearman's rho=0.301, p=0.013). Patients with low levels of sPDL1 at diagnosis (< 1.92 ng/mL) showed a better OS and PFS than patients with a high sPDL1. The baseline sPDL1 before treatment was higher in the progressive disease group than in the stable disease and partial response groups. Patients whose sPDL1 increased after the first cycle of chemotherapy showed worse PFS and OS. Following disease progression, sPDL1 increased compared with the baseline. CONCLUSION: sPDL1 at prechemotherapy confers a prognostic value for PFS and OS in GC patients under palliative first-line chemotherapy. Dynamics of sPDL1 during chemotherapy correlates with disease progression.

The prognostic role of soluble transforming growth factor-ß and its correlation with soluble programmed death-ligand 1 in biliary tract cancer.

BACKGROUND: This study aimed to evaluate the association between soluble TGF-ß (sTGF-ß) and soluble PD-L1 (sPDL1), the dynamics of sTGF-ß during treatment and its prognostic role in biliary tract cancer (BTC). METHODS: The study population consisted of 90 BTC patients with first-line chemotherapy (cohort 1) and 35 BTC patients with second- or third-line chemotherapy (cohort 2). Plasma sTGF-ß and sPDL1 levels were measured using an enzyme-linked immunosorbent assay. RESULTS: In both groups, sTGF-ß was positive correlated with sPDL1 for baseline and change values after treatment. sTGF-ß was elevated at disease progression compared to baseline in cohort 1 (P < .001). Increased sTGF-ß after treatment revealed worse DFS and OS (P = .024, P = .028, respectively) in cohort 1 and significantly shorter OS (P = .020) in cohort 2. In multivariable analysis, this prognostic value of increased sTGF-ß for OS retained its significance in both cohorts (Hazard ratio (HR) = 1.8, 95% CI, 1.1-3.0, P = .028, in cohort 1; HR = 4.7, 95% CI, 1.5-14.6, P = .007, in cohort 2). CONCLUSIONS: In BTC, sTGF-ß was positively correlated with sPDL1 for baseline and changes after chemotherapy, and increased as tumour burden. sTGF-ß could be associated with survival; particularly, an elevated value after treatment suggests worse prognosis.

Inhibition of ATR Increases the Sensitivity to WEE1 Inhibitor in Biliary Tract Cancer.

PURPOSE: Currently, the DNA damage response (DDR) pathway represents a key target for new cancer drug development. Advanced biliary tract cancer (BTC) has a poor prognosis because of the lack of efficacious treatment options. Although DNA repair pathway alterations have been reported in many patients with BTC, little is known regarding the effects of DDR-targeted agents against BTC. MATERIALS AND METHODS: In this study, nine BTC cell lines were exposed to the WEE1 inhibitor (AZD1775). In vitro, MTT assay, colony-forming assay, cell cycle analysis, phospho-histone H3 staining assay, Transwell migration assay, and western blot were performed. Then, to enhance the antitumor effect of AZD1775, the combination treatment of WEE1 inhibitor and ataxia telangiectasia mutated and Rad3 related (ATR) inhibitor (AZD6738) was conducted using MTT assay and comet assay. Finally, HuCCT-1 and SNU2670 xenograft models were established to confirm the anti-tumor effect of AZD1775 alone. Furthermore, the combination treatment was also evaluated in SNU2670 xenograft models. RESULTS: AZD1775 blocked the phosphorylation of CDC2 and CDC25C in all cell lines, but significantly increased apoptosis and S phase arrest in sensitive cells. However, increased p-ATR and phosphorylated ataxia telangiectasia mutated levels were observed in less sensitive cells. In addition, in vitro and in vivo data illustrated that AZD1775 combined with AZD6738 exerted more potent anti-tumor effects than either drug alone. Although WEE1 inhibition has promising anti-tumor effects in some BTC cells, the addition of ATR inhibitors could enhance its efficacy. CONCLUSION: Taken together, this study supports further clinical development of DDR-targeted strategies as monotherapy or combination regimens for BTC.