Reduction in the formation of carcinogen-induced transformed foci by pencillin G sodium in the C3H/10T1/2 CL8 cell lines.

The C3H/10T1/2 CL8 cell line is being widely used to study mechanisms of malignant transformation in vitro. As currently employed, the standard assay system uses a combination of penicillin (100 I.U./ml) and streptomycin (50 micrograms/ml) to reduce the occurrence of bacterial contamination. The penicillin component of this mixture has been discovered to cause a reduction in the number of transformed foci which develop after exposure of cells to MCA, DMBA and X-rays. This reduction is dose dependent; 500 I.U./ml virtually eliminates transformation, while 100 I.U./ml causes an approximate 50% decrease in the number of foci. This effect does not appear to be due to overt toxicity and is largely reversible on removal of the antibiotic. Gentamicin (25 micrograms/ml) causes no reduction in the formation of transformed foci when compared to cultures maintained in antibiotic-free medium and offers the advantages of chemical stability, a wider spectrum of antibacterial activity in comparison with penicillin/streptomycin and, in addition, is active against many mycoplasma. It is suggested that future studies with this cell line should ideally be performed without antibiotics or should employ Gentamicin for antibacterial protection.     

Evaluation of the potential genotoxicity of chromium picolinate in mammalian cells in vivo and in vitro.

Chromium picolinate (CrPic) is a synthetic nutritional supplement primarily used for weight loss and muscle building. Recent studies have indicated that CrPic might be genotoxic and these findings together with the wide-spread consumer use, have increased the concern about its safety. In the present study we investigated the potential genotoxicity of CrPic in mice given a single intraperitoneal injection (up to 3 mg/kgb.wt.) by evaluating the frequency of micronucleated polychromatic erythrocytes (fMNPCE) in peripheral blood, and DNA damage in lymphocytes and hepatocytes. The fMNPCE was evaluated after 42 h and DNA damage after 16 h. Using the Comet assay DNA damage was also monitored in extended-term cultures of human lymphocytes and in L5178Y mouse lymphoma cells that had been exposed for 3h to 500 microM CrPic under different exposure conditions. A slight, but significant CrPic-induced increase in DNA damage (P<0.001) was observed in the human lymphocytes, but only when these cells were exposed in the absence of serum. In all other experiments CrPic was found to be without genotoxic effects, both in vivo and in vitro. Taken together, our results suggest that a high concentration of CrPic might be DNA damaging, but only under non-physiological conditions.     

Establishment of a cloned line of Lewis lung carcinoma cells adapted to cell culture

A cloned line of cells adapted to culture has been isolated from the Lewis Lung Carcinoma and has been designated the Lewis lung carcinoma line 1 (LLC1). It grows as a monolayer culture in RPMI 1640 medium supplemented with 2% fetal calf serum with a plating efficiency of about 94% and a doubling time of 21 h. LLC1 cells remain highly tumorigenic in C57B1 mice and produce primary tumors and lung metastases histologically indistinguishable from the original tumor line. The doubling time for a subcutaneous tumor derived from LLC1 cells was 23 h for a tumor mass of about 0.1 g and 40 h for a tumor mass of about 1 g. The cell line forms discrete colonies on a plastic substrate and can be used in a focus assay to determine drug induced cytotoxicity. Results with a number of chemotherapeutic agents are reported; in general, sensitivity measured in vitro does not correspond with published reports of sensitivity of the Lewis Lung carcinoma in vivo.