ESR1 and breast cancer: Additionally, a significant increase in CACNG4 mRNA expression was observed in ER-positive breast cancer patients compared to ER-negative cases, as illustrated in Fig. 4A. PKMYT1 mRNA expression was up-regulated in patients aged 50 years and older, as well as in patients with HER2-positive status, as displayed in Fig. 4B. Analysis revealed a significant increase in EPYC mRNA expression levels in hormone receptor-positive (HR+) breast cancer patients compared to HR-negative (HR-) individuals.