Indentification of breast cancer subtypes sensitive to HCQ-induced autophagy inhibition

Background: Breast cancer is the most frequent carcinoma in females, which could be classified to 4 subtypes and the current treatment is still far from satisfactory. In this study, we explored the effects of autophagy inhibition on certain subtypes of breast cancer and the molecular mechanism underlying the different response for breast cancer subtypes initially. Methods: Autophagy inhibitor hydroxychloroquine (HCQ) was used to identify the sensitivity of breast cancer subtypes to autophagy inhibition in the present study. Cell proliferation and cell invasion were assessed by Cell Counting Kit-8 assay (CCK-8) and transwell assay, respectively. Immunofluorescence staining and western blotting were applied to evaluate cell autophagy. In addition, levels of Ras/Raf/ERK signaling pathway were evaluated by western blotting. Results: Our results showed that HCQ treatment suppressed breast cancer cell proliferation and migration in especially SUM 190 cells, which was most sensitive. Furthermore, HCQ inhibited cell autophagy in breast cancer cells by regulating levels of p62, LC3-I and LC3-II. Moreover, the expression of Ras was significant lower than other breast cancer cells. HCQ treatment markedly inhibited the activation of Ras/Raf/ERK signaling in SUM190 cells. Conclusion: To conclude, basal-like breast cancer represented by SUM-190 cells may be most sensitive to HCQ induced autophagy inhibition and the mechanism might be relative to Ras/Raf/ERK signaling pathway.