Association of SIBA treatment and a Met-depleted diet inhibits in vitro growth and in vivo metastatic spread of experimental tumor cell lines.

We have used 5'-deoxy-5'-S isobutyl-thioadenosine (SIBA), an analog of S-adenosylhomocysteine, alone or in association with a methionine-depleted diet in order to obtain an antitumoral effect in two different tumor models: a transplantable rat rhabdomyosarcoma (RMS-J1) induced by i.m. injection of nickel and the well-known Lewis lung carcinoma (3LL) of C57BL/6 mice.

Decreased rat rhabdomyosarcoma pulmonary metastases in response to a low methionine diet.

Many Experimental and human tumor cell lines have been previously described as being dependent upon exogenous methionine for their in vitro proliferation. The rationale of the experiments described herein was to decrease the in vivo growth of malignant tumors by reducing the exogenous methionine available in diets fed to Wistar AG rats bearing the highly metastatic rhabdomyosarcoma, RMS-J1. The methionine content in the diet was reduced either by replacing casein (diet 1) with soybean protein (diet 4), or by lowering the amount of soybean protein in the diet (from 23 g/100 g to 12 g/100g) (diet 5), or by using a crystalline amino acid-defined mixture as the source of protein (diet 7).