Mononuclear cells release low molecular weight factors with anti-cancer activity: A lower level of production by cell of cancer patients

Following the clinical observations that tumor metastases are extremely rare in striated muscles we defined recently a low molecular weight factor which is released by muscle cells (muscle factor, MF) and possesses specific antiproliferative activity against tumor cells. We demonstrate that peripheral blood mononuclcar cells constitutively release low molecular, weight factor (LMF) similar to the MF which is capable of inhibiting in vitro the proliferation of carcinoma, melanoma, leukemia and lymphoma cell lines. The proliferation of normal cells such as bone marrow or fibroblasts was not inhibited but slightly stimulated following incubation with the LMF. Biochemical purification of this factor by several HPLC steps revealed that the inhibitory activity against tumor cells was concentrated within two definitive peaks. The LMF affects tumor cell growth by arresting them in the G ₀/G ₁ of the cell cycle and its activity is species and tumor non-specific. In vivo studies in melanomabearing mice revealed that the LMF inhibited melanoma growth when given either intraperitoneally or orally. Mononuclear cells from cancer patients with different malignancies (non-Hodgkin lymphoma, malignant melanoma, colon carcinoma and carcinoma of the rectum) secreted lower level of LMF in comparison to healthy subjects. The capability of the LMF to inhibit tumor cell growth and promote normal cell proliferation combined with its bioavailability in vivo may lead to its potential therapeutic and diagnostic use.