Functional interplay between LSD1 and HDAC6 supports malignant phenotypes in breast cancer models and is associated...

LSD1/KDM1A and HDAC6 have each been linked to breast cancer progression, but whether they are functionally connected and whether depletion of either enzyme alters Notch-related proteins remain unclear.

LSD1 and HDAC6 expression was examined in TCGA and GEO datasets, a tissue microarray of 145 breast cancers and 15 peritumoral tissues, and breast cancer cell lines. We altered LSD1 and HDAC6 expression by knockdown or overexpression and assessed molecular readouts, cell phenotypes, reciprocal migration rescue, and xenograft growth. ChIP-qPCR assessed LSD1 occupancy and H3K4me2/H3K9ac enrichment at two HDAC6 promoter regions. Migration rescue was evaluated in MDA-MB-231 cells using Matrigel-free Transwells. NOTCH1, NICD, HES1, and HEY1 were measured after each perturbation.

LSD1 mRNA was higher in tumors in all four public cohorts, whereas HDAC6 mRNA showed no consistent tumor-normal difference. Neither gene was significantly associated with survival, and clinicopathological associations were limited or inconsistent. Immunohistochemistry showed a clearer tumor-peritumoral difference for HDAC6 than for LSD1; several cancer cell lines also expressed more LSD1 or HDAC6 than MCF-10 A. LSD1 knockdown reduced HDAC6 mRNA and protein. ChIP-qPCR detected LSD1 enrichment at two HDAC6 promoter regions; LSD1 knockdown reduced this enrichment and increased H3K4me2 and H3K9ac at both regions. LSD1 or HDAC6 depletion reduced proliferation, migration, invasion, and colony formation and slowed xenograft growth. In Matrigel-free MDA-MB-231 Transwell assays, reciprocal overexpression partially rescued migration after either knockdown, although migration remained below the control level. Depletion of either enzyme also reduced full-length NOTCH1, NICD, HES1, and HEY1.

The data support a functional relationship between LSD1 and HDAC6 in the models examined. ChIP-qPCR detected LSD1 enrichment at the two HDAC6 promoter regions tested. Depletion of either enzyme also reduced several Notch-related proteins.