Adenosine and other low molecular weight factors released by muscle cells inhibit tumor cell growth
Fishman, P.; Bar-Yehuda, S.; Vagman, L.
Cancer Research 58(14): 3181-3187
1998
ISSN/ISBN: 0008-5472 PMID: 9679987 Document Number: 488070
In this study, we investigated the basis of the resistance of muscles to tumor metastases. We found that a low molecular weight fraction (Mr <3000) of skeletal muscle cell-conditioned medium (MCM) markedly inhibits the proliferation of carcinoma, sarcoma, or melanoma cell lines in vitro. The MCM exerts a cytostatic effect on tumor cell growth and arrests the cells in G0/G1 of the cell cycle. However, normal cell proliferation of cells such as bone marrow cells or fibroblasts was found to be refractory to the influence of the MCM. A reduction in melanoma growth was observed in mice treated with the MCM. Adenosine was identified as one of the active components in the MCM by using high-performance liquid chromatography separations, mass spectra, and nuclear magnetic resonance analyses. At a concentration of 4 microM, equal to that found in the MCM, adenosine inhibits the proliferation of tumor cell lines (Nb2 lymphoma, K-562 leukemia, and LNCaP prostate carcinoma cells) while stimulating the proliferation of normal murine bone marrow cells. By similar methods, additional inhibitory components were detected in the MCM in a molecular mass range of 600-800 Da. The ability of adenosine and other low molecular weight components to specifically inhibit tumor cell growth in vitro and in vivo may account for the resistance of muscle to tumor metastases.