Long-term tumor resistance induced by laser photo-immunotherapy

An ideal treatment modality for metastasizing tumors should eradicate the p rimary tumor and elicit a systemic, tumor-selective response leading to eli mination of metastases and long-term tumor resistance. Also, it should be i nduced by local treatment at the primary site, to limit adverse systemic ef fects. A new method for treating metastatic tumors which utilizes a combina tion of a near-infrared laser, a photosensitizer and an immunoadjuvant has been developed. It involves intra-tumor injection of the sensitizer/adjuvan t solution, followed by local non-invasive laser irradiation. it-has produc ed regression and total eradication of treated primary tumors and untreated metastases at remote sites against mammary tumors in rats. Successfully tr eated tumor-bearing vats showed total tumor resistance to subsequent tumor rechallenge. Our histochemical results showed that: sera from cured tumor-b earing rats contained antibodies that bound strongly to the plasma membrane of both living and preserved tumor cells. Western blot analysis of tumor c ell proteins using sera from successfully treated rats as the source of pri mary antibodies also showed distinct bands, indicating induction of tumor-s elective antibodies. Our findings indicate that a systemic, long-term effec t on metastatic tumors can be induced by local application of laser photo-i mmunotherapy, Int. j. Cancer 81:808-812, 1999, (C) 1999 Wiley-liss, Inc.