Combined therapeutic effects of conventional agents and an immunomodulator, PSK, on rat prostatic adenocarcinoma

Growth alteration effects of an immunomodulator, PSK, were investigated individually and in association with conventional chemotherapeutic agents cyclophosphamide, cisplatin and fluorouracil in an experimental prostatic cancer model. Copenhagen rats had subcutaneous tumors induced by injections of cells cultured in vitro from a highly metastatic hormonally unresponsive subline of the Dunning rat prostatic tumor, MAT-LyLu. Treatment with conventional agents and the immunomodulator agent individually and in combination began three days after tumor cell inoculation. PSK used alone was not able to significantly influence tumor growth. In appropriate doses, each conventional agent significantly retarded tumor growth. Used in combination, PSK and conventional agents retarded tumor growth locally and decreased metastatic spread of the tumor. Animals receiving combination therapy had increased life spans over those animals receiving single standard chemotherapeutic agents. Immunomodulation with PSK may enhance the antineoplastic effects of chemotherapeutic agents and offer a treatment option for hormone resistant prostatic cancer.