CoAsy knockdown in TNBC cell lines resulted in no overt effect on cell proliferation in vitro

Triple-negative breast cancer (TNBC) remains the most challenging breast cancer subtype to treat. CoA synthase (CoAsy) is a bifunctional enzyme, encoded by the COASY gene, which catalyzes the last two steps of CoA biosynthesis. COASY has been reported as a hit in several large RNAi library screens for cancer. Therefore, we sought to investigate the dependency of TNBC cell line proliferation on CoAsy expression. Initially, knockdown of CoAsy expression was achieved by RNAi and reduced proliferation was observed in two TNBC cell lines, HCC1806 and MDA-MB-231. To further investigate the role of CoAsy, we established stable inducible shRNA cell lines from the same TNBC cell lines as well as the normal-like breast cell line MCF10A. Three separate cell lines, each expressing one of three different shRNA constructs targeting COASY, and a non-targeted shRNA control cell line were generated from each parent cell line. The induction of COASY shRNA for 4 days resulted in >99% knockdown of CoAsy for all three COASY shRNA constructs. However, this robust knockdown of CoAsy protein expression had no detectable impact on cell growth with 4-day induction times. Even 8-day induction times resulted in no apparent impact on cell growth. There was also no effect of CoAsy knockdown on the rate of cell migration. Measurement of CoA levels in cell lysates indicated that CoAsy knockdown reduced CoA to approximately half the normal level. Thus, CoAsy knockdown showed no detectable effect on the in vitro proliferation and migration of these cell lines possibly due to the cell's ability to maintain adequate levels of CoA through some unknown mechanism.