PGR and breast cancer: To further explore the relationship between ATM and ATG4C genes we calculated the correlations between ATM and ATG4 genes in all four subtypes of breast cancer based on published classifications [30]: two estrogen receptor (ER)-positive subtypes separated mainly by relatively low (luminal A) and high (luminal B) expression of proliferation-related genes, a subtype enriched for HER2-amplified tumors [human epidermal growth factor receptor 2 (HER2)-enriched], a subtype associated with triple-negative [lacking expression of ER, progesterone receptor (PR), and HER2] tumors (basal-like).