Finally, using primary cultures of human breast tumors, and given that Pit-1 protein levels seem to be a better marker for 1, 25D-sensitivity than Pit-1 mRNA levels, we evaluated cell proliferation after 3-Epi, cisplatin, and 3-Epi+cisplatin treatment, and correlated the effect on cell proliferation with Pit-1 protein expression. The gene discussed is POU1F1; the disease is breast neoplasm.