LSD1 inhibition suppresses ASCL1 and de-represses YAP1 to drive potent activity against neuroendocrine prostate cancer.

Lysine-specific demethylase 1 (LSD1 or KDM1A ) has emerged as a critical mediator of tumor progression in metastatic castration-resistant prostate cancer (mCRPC). Among mCRPC subtypes, neuroendocrine prostate cancer (NEPC) is an exceptionally aggressive variant driven by lineage plasticity, an adaptive resistance mechanism to androgen receptor axis-targeted therapies. Our study shows that LSD1 expression is elevated in NEPC and associated with unfavorable clinical outcomes. Using genetic approaches, we validated the on-target effects of LSD1 inhibition across various models. We investigated the therapeutic potential of bomedemstat, an orally bioavailable, irreversible LSD1 inhibitor with low nanomolar potency. Our findings demonstrate potent antitumor activity against CRPC models, including tumor regressions in NEPC patient-derived xenografts. Mechanistically, our study uncovers that LSD1 inhibition suppresses the neuronal transcriptional program by downregulating ASCL1 through disrupting LSD1:INSM1 interactions and de-repressing YAP1 silencing. Our data support the clinical development of LSD1 inhibitors for treating CRPC - especially the aggressive NE phenotype. Statement of Significance: Neuroendocrine prostate cancer presents a clinical challenge due to the lack of effective treatments. Our research demonstrates that bomedemstat, a potent and selective LSD1 inhibitor, effectively combats neuroendocrine prostate cancer by downregulating the ASCL1- dependent NE transcriptional program and re-expressing YAP1.

Implication of BRCA1 gene in breast cancer.

Breast cancer susceptibility gene (BRCA1) is known to be responsible for hereditary breast and ovarian cancer. This gene is highly penetrant conferring a risk for 0.92 by the age of 70. Germline mutation in this gene leads to susceptibility to breast and ovarian cancer, with a genotype phenotype correlation. Frequency of mutations of this gene in normal population of breast cancer is low suggesting that the effort of primary screening for BRCA1 gene should be restricted to only familial cases with a strong history of breast and ovarian cancer. Recent studies indicate that BRCA1 is a tumor suppressor gene responsible for both normal development and carcinogenesis of the breast. Normal function elucidated so far, reveal BRCA1 to be a multifunctional protein involved in DNA repair, cell cycle regulation and transcription. There is circumstantial evidence that gene interacts with p53, a protein involved in cell cycle control, DNA repair and apoptosis.

Effect of omega-3 fatty acid (docosahexanoic acid) on BRCA1 gene expression and growth in MCF-7 cell line.

Recently, we have demonstrated that omega-6 fatty acid linoleic acid (LA) in presence of estradiol (E2) enhances proliferation and anchorage independent growth with down regulation of BRCA1 mRNA expression in MCF-7 cell line. Since omega-3 fatty acid (docosahexanoic acid, DHA) is known to block the promoting effect of omega-6 polyunsaturated fatty acid (LA), we wanted to see whether addition of DHA can inhibit the growth of MCF-7 cells which are exposed to LA + E2 and any alteration of BRCA1 mRNA expression could be seen in DHA treated culture. Experiments on MCF-7 cells with DHA revealed both decrease in proliferation and anchorage independency as compared to controls; while no change of BRCA1 mRNA expression was observed. Further, when DHA was administered to cells along with LA + E2, no change in BRCA1 expression was observed, however, a marked decrease in proliferation and soft agar colony formation was evident, indicating inhibition of MCF-7 cells following DHA treatment. Flow cytometric analysis showed that DHA treated cells either alone or in combination with LA + E2 induced marked G1/S and G2/M arrest of the cells, suggesting the inhibitory effect of DHA at this phase of cell cycle. However, neither typical DNA ladder nor fragmented nuclei or apoptotic bodies were observed, ruling out presence of apoptosis following DHA treatment.

Reduced expression of the BRCA1 gene and increased chromosomal instability in MCF-7 cell line.

Using clonal cell cultures, a significant increase in chromosomal aberrations (aneuplolidy, dicentrics and chromatid breaks) were observed in MCF-7 cells compared with HeLa. BRCA1 expression was lower in MCF-7 cells than in HeLa cells. Since BRCA1 is known to play a role in the maintenance of chromosomal integrity, the increase in chromosomal aberrations in MCF-7 clones suggests that downregulation of BRCA1 expression could be one of the possible mechanisms for increased chromosomal instability in this cell line.

Effect of omega-6 polyunsaturated fatty acid (linoleic acid) on BRCA1 gene expression in MCF-7 cell line.

Dietary unsaturated fatty acids have been implicated in breast cancer. Since mutations in BRCA1 gene are known to predispose to breast cancers, and BRCA1 gene is known to be regulated by estradiol, the effect of linoleic acid, an omega-6-polyunsaturated fatty acid, with and without estradiol was studied for the expression of BRCA1 gene, in MCF-7 cell line, which has only one wild type allele. MCF-7 cells exposed to either linoleic acid or estradiol showed relatively greater number of colonies on soft agar, extent of proliferation and BRCA1 mRNA expression compared with controls. However, cells treated with both linoleic acid and estradiol showed significantly higher number of colonies, proliferation index and appreciably decreased expression of BRCA1 mRNA compared with controls or cells treated with linoleic acid or estradiol alone. The synergistic effects of these two agents were abrogated when indomethacin, an inhibitor of prostaglandin pathway, was added to the culture. From these observations it appears that diet rich in omega-6-polyunsaturated fatty acid like linoleic acid and endogenous estrogen may modulate BRCA1 gene expression thereby promoting breast cancer.