ESR1 and ovarian serous adenocarcinoma: OLFM4 and ERα expression in SKOV3 cells, a moderately-differentiated ovarian serous adenocarcinoma cell line, was higher than the expression in HO8910-pm, a poorly-differentiated ovarian serous adenocarcinoma cell line (Figure 4), further suggesting the correlation of OLFM4 expression with ERα expression and degree of tumor differentiation.