CLOCK and breast carcinoma: More recently, a number of in vitro studies have investigated clock gene expression profiles in a time-dependent manner in various breast cancer cell lines, including: MCF7 and T47D (luminal A subtype); HCC-1954 (HER2 positive subtype); MCF10A and MDA-MB-231 (basal-like subtype), and others (67, 80–83).