[Characteristics in antitumor effects of organic silicon related compounds]

To investigate the characteristics in antitumor effects of 2-trimethylsilylethylthioethylamine(KAS-010) and its conjugate with 5-FU (KAS-011), the antitumor and immunomodulating activities of these silicon compounds were examined with various systems. Both KAS-010 and KAS-011 administered orally was found to be effective to B 16 melanoma, Meth A sarcoma and MM 46 mammary carcinoma in vivo. On the other hand, KAS-011 administered orally exhibited a marked antitumor activity against L 1210 leukemia bearing mice. Furthermore, these silicon compounds inhibited significantly metastases to the lymph nodes and lung of Lewis lung carcinoma implanted id into the right ear of BDF1 mice. Especially, KAS-011 in combination with tumor amputation resulted in a remarkable prolongation of the survival time (% ILS: 93.8%) in this antimetastatic model. The cell killing effect was mainly dependent on the exposure time of these silicon compounds in cultured KB and human lung cancer (OAT) cells. Moreover, a significant increase of delayed type hypersensitivity reaction (DTHR) to sheep red blood cell (SRBC) induced by KAS-010 was seen in old aged mice. The DTHR in B 16 melanoma and Ehrlich carcinoma bearing mice treated with KAS-010 was significantly higher than those of non-treated tumor bearing mice, indicating an enhanced cellular immunity to KAS-010 possibly resulting in a remarked antitumor effect. We also found that tumor free mice treated these silicon compounds were acquired specific tumor immunity to Meth A sarcoma and MM 46 mammary carcinoma.