The sodium-dependent phosphate transporter NaPi2b encoded by SLC34A2 gene is expressed in 80-90% of epithelial ovarian cancers and used as a target for therapeutic antibodies XMT-1536, and XMT-1592, which are derived from MX35 antibodies and used in clinical trials for the treatment of ovarian and lung cancers. In this work, we demonstrated that the expression of the human NaPi2b (hNaPi2b) transporter is downregulated in the tumors of patients receiving neoadjuvant therapy and during the development of disease. The data suggest that the level of expression of the SLC34A2 gene can serve as a potential marker for the monitoring and predicting responses to neoadjuvant and targeted therapy in patients with ovarian cancer.