Mononuclear cells release low molecular weight factors with anti-cancer activity: A lower level of production by cells 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 anti-proliferative activity against tumor cells. we demonstrate that peripheral blood mononuclear 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 G0/G1 of the cell cycle and its activity is species and tumor non-specific. In vivo studies in melanoma- bearing 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.

Anti-tyrosinase antibodies in malignant melanoma.

Anti-tyrosinase antibodies were measured by enzyme-linked immunosorbent assay in sera of patients with malignant melanoma with either metastatic disease or no evidence of disease, in patients with melanoma and associated hypopigmentation (MAH), in patients with vitiligo and in healthy volunteers. The mean relative absorbance (Arel) was calculated by dividing the absorbance of each sample by the mean value for the control group. Using this method, the Arel of the control group was 1.000(SE 0.083). Arel of patients with metastatic disease (1.516; SE 0.225) was significantly higher (P = 0.03) than the value for the controls, but insignificantly higher than that for patients with no evidence of disease (1.216; SE 0.148). Patients with no evidence of disease, in whom the primary lesion originated in the lower limb, had a significantly higher (P = 0.01) Arel than the healthy volunteers. Patients with metastatic disease showed higher Arel if their primary lesions were confined to the area of the head and neck or to the lower limb. Patients with vitiligo had higher Arel values for their anti-tyrosinase antibody than any of the other groups. However, those with melanoma and MAH (vitiligo-like) had the same Arel of anti-tyrosinase antibodies as the controls or the patients with metastatic melanoma. This observation reflected the possible absorption of anti-tyrosinase antibodies to melanoma antigens, and pointed to the participation of anti-tyrosinase antibodies in the destruction of normal melanocytes in patients with melanoma, as part of the immune reaction towards this disease.