L-arginine supplementation does not affect chemically induced carcinogenesis and tumor growth in BALB-c mice.

UNLABELLED: T-cell zeta-chain downregulation is common in various types of cancer and it is proposed as a mechanism of cancer immunosubversion. L-arginine consumption by arginase rich suppressor myeloid cells has been incriminated. The effect of L-arginine supplementation on chemically induced carcinogenesis and tumor growth in mice was evaluated.
METHODS: Eight-week old female BALB-c mice were used. Ten mice were injected i.m. with 0.6 mg methylcholanthrene (MCA) once. Ten mice were injected with MCA once and were receiving L-arginine supplementation (5% in animal drinking water) continuously during the study. Mice with cancer were sacrificed 12 weeks after.
RESULTS: From the 10 MCA injected mice 6 developed sarcoma. From the 10 MCA injected mice that were receiving L-arginine supplementation 7 developed sarcoma. L-arginine supplementation did not affect MCA induced carcinogenesis (p=1.0, Fisher's exact test). The weight of tumors was not different between the tumors derived from mice that were or were not receiving L-arginine supplementation (1088.3+/-590.2 mg vs. 969.6+/-608.1 mg respectively, p=0.729, unpaired t-test).
CONCLUSION: L-arginine supplementation does not affect chemically induced carcinogenesis and tumor growth in BALB-c mice. Although zeta-chain downregulation could be a mechanism of cancer immunosubversion there are enough other cancer immunosubversion mechanisms that were not overwhelmed by L-arginine supplementation. Additionally, except cancer immunosubversion, cancer immunoselection is another, possibly more significant, mechanism of tumor escape from immunosurveillance.