Moreover, we observed a marginal decrease in the proliferation of non-TNBC cell lines upon the downregulation of TBC1D9. However, an increase in migratory and tumorigenic potential was observed upon knockdown (KD) of TBC1D9 in both non-TNBC and TNBC cell lines by regulating the expression of ARL8A, PLK1, HIF1α, STAT3, and SPP1. The present study sheds light on the role of TBC1D9 as a modulator of BC aggressiveness and underlines the fact that the aggressiveness of TNBC could be due to the lack of expression of TBC1D9. The gene discussed is ARL8A; the disease is breast cancer.