Anti-apoptotic protein BCL-XL as a therapeutic vulnerability in gastric cancer

Background: New therapeutic targets are needed to improve the outcomes for gastric cancer(GC) patients with advanced disease. Evasion of programmed cell death(apoptosis) is a hallmark of cancer cells and direct induction of apoptosis by targeting the pro-survival BCL2 family proteins represents a promising therapeutic strategy for cancer treatment. Therefore, understanding the molecular mechanisms underpinning cancer cell survival could provide a molecular basis for potential therapeutic interventions. Method: Here we explored the role of BCL2L1 and the encoded anti-apoptotic BCL-XL in GC. Using Droplet Digital PCR(ddPCR) technology to investigate the DNA amplification of BCL2L1 in GC samples and GC cell lines, the sensitivity of GC cell lines to selective BCL-XL inhibitors A1155463 and A1331852, pan-inhibitor ABT-263, and VHL-based PROTAC-BCL-XL was analyzed using(CellTiter-Glo) CTG assay in vitro. Western Blot(WB) was used to detect the protein expression of BCL2 family members in GC cell lines and the manner in which PROTAC-BCL-XL kills GC cells. Coimmunoprecipitation(Co-IP) was used to investigate the mechanism of A1331852 and ABT-263 kills GC cell lines. DDPCR, WB, and real-time PCR(RTPCR) were used to investigate the correlation between DNA, RNA, protein levels, and drug activity. Results: The functional assay showed that a subset of GC cell lines relies on BCL-XL for survival. In gastric cancer cell lines, BCL-XL inhibitors A1155463 and A1331852 are more sensitive than the pan BCL2 family inhibitor ABT-263, indicating that ABT-263 is not an optimal inhibitor of BCL-XL. VHL-based PROTAC-BCL-XL DT2216 appears to be active in GC cells. DT2216 induces apoptosis of gastric cancer cells in a time-and dose-dependent manner through the proteasome pathway. Statistical analysis showed that the BCL-XL protein level predicts the response of GC cells to BCL-XL targeting therapy and BCL2L1 gene CNVs do not reliably predict BCL-XL expression.Conclusion: We identified BCL-XL as a promising therapeutic target in a subset of GC cases with high levels of BCL-XL protein expression. Functionally, we demonstrated that both selective BCL-XL inhibitors and VHL-based PROTAC BCL-XL can potently kill GC cells that are reliant on BCL-XL for survival. However, we found that BCL2L1 copy number variations(CNVs) cannot reliably predict BCL-XL expression, but the BCL-XL protein level serves as a useful biomarker for predicting the sensitivity of GC cells to BCL-XL-targeting compounds. Taken together, our study pinpointed BCL-XL as potential druggable target for specific subsets of GC.

Bexarotene combined with lapatinib for the treatment of Cushing’s disease:evidence based on drug repositioning and experimental confirmation

Dear Editor,Cushing’s disease(CD)is a rare disease manifested as Cushing’s syndrome caused by adrenocorticotropic hormone(ACTH)consistently over-secreted by adrenocorticotropic adenomas,followed by stimulation of the adrenal gland to secrete considerable cortisol,triggering metabolic dysfunction,and leading to death from complications.However,pituitary adrenocorticotropic adenoma-directed drugs can only inhibit ACTH secretion or hamper tumour growth,which limits their clinical applications.Recently,Nur77(also known as NR4A1 and NGFI-Ba,a kind of nuclear receptor),an important positive transcription regulator of pro-opiomelanocortin(POMC),the precursor of ACTH,has been regarded as a promising CD target.1 Hence,it would be promising to identify a combination treatment that targets Nur77 and another CD target to cover hormone normalisation in the short term and tumour suppression or even elimination in the long term.