STX17 and breast cancer: In contrast, a recent study investigating the role of TPC2 in the autophagy of cancer cells reported that overexpression of TPC2 in the Hela human cervical cancer cell line and in a 4T1 mouse breast cancer cell line diminished autophagosomal–lysosomal fusion, resulting in the accumulation of microtubule-associated protein light chain 3 (LC3)-II and syntaxin 17 (STX17)-positive autophagosomes (Sun and Yue, 2018).