[Preliminary study on skeletal muscle derived tumor suppressor].

OBJECTIVE

To investigate the effect of new born rat skeletal muscle conditioned medium (MCM) on proliferation of tumor cells, and its physicochemical characteristics and mechanisms of action.

METHODS

The effects of MCM were tested on a variety of cells by MTT assay. MCM was also tested following ultrafiltration, boiling at 100 degrees C and treatment with trypsin. Morphology and apoptosis of the MCM-treated cells were examined.

RESULTS

Proliferation of mouse myeloma SP2/0, rat carcino-sarcoma Walker 256, and tumor cell lines of human origin, including leukemia K562 and HL-60, colon adenocarcinoma LS-174-T, prostatic carcinoma PC3-M, and lung adenocarcinoma with low(PLA801-C) and high(PLA801-D) metastatic potential were significantly decreased when cultured with MCM(P < 0.01-0.05) in a dose-dependent manner. The proliferation of normal cells(RGP-2 rabbit joint epiphysial disk cells) was not affected by MCM. Proliferation of the lung adenocarcinoma with high metastatic potential was more susceptible to the growth inhibitory effect of MCM as compared to that with low metastatic potential. On ultrafiltration, the inhibitory activity of MCM existed in the fraction with a molecular weight < or = 10,000. It was trypsin resistant but thermolabile. Apoptosis was not seen but the cytoplasmic membrane of tumor cells was destroyed after cultured in MCM.

CONCLUSION

Rat skeletal muscle cells produce low molecular weight tumor suppressor(s) capable of selectively inhibiting tumor cell proliferation in vitro. Its activity is neither species- nor tumor-specific. The skeletal muscle derived tumor suppressor(s) may play a key role in the rarity of tumor metastases in skeletal muscles.