ABCG2 and triple-negative breast carcinoma: In 2017, Xing et al. found that ALDH1 and ABCG2 were enhanced in primary foci and metastatic lymph node from patients with triple-negative breast cancer with qRT-PCR, western blotting and MTT assay of mRNA expression, protein expression and proliferation of MDA-MB-231 cells, respectively; and the authors proposed that ALDH1 and ABCG2 may affect the drug resistance [13].