Role of arginine and its methylated derivatives in cancer biology and treatment

**Background** L-arginine is an essential amino acid required for normal cell growth and metabolism. Both deprivation and excessive supplementation of arginine can influence cell function, including proliferation and death. This narrative review synthesises evidence on the role of arginine and its methylated derivatives in tumour biology and therapy, with a focus on the mechanisms underlying their effects on cancer cells.

**Methods** The authors review experimental studies, including in vitro cell culture experiments and in vivo animal tumour models. Key studies examined include: arginine deprivation in various tumour cell lines; supplementation with L-arginine, D-arginine, and DL-arginine in Wistar rats bearing Yoshida's sarcoma and Swiss mice bearing Ehrlich carcinoma; treatment with NG-hydroxymethyl arginine in Ehrlich ascites tumour and Lewis lung tumour models; and studies on methylated arginine derivatives in human cancer cell lines (HT-29 colon carcinoma, P-388 lymphoma, PC-3 prostate carcinoma, K-562 erythroleukaemia).

**Key Results** Arginine deprivation caused selective death of malignant cells while normal cells survived. In co-cultures, normal cells survived arginine deprivation whereas tumour cells died. D-arginine (500 mg/kg orally) inhibited Yoshida's sarcoma growth by 50% (p < 0.05) but only 20% inhibition (not statistically significant) in Ehrlich carcinoma. L-arginine enhanced tumour growth: 40% enhancement (p < 0.05) in Yoshida's sarcoma (400 mg/kg i.p.) and 40% enhancement (p < 0.05) in Ehrlich carcinoma (500 mg/kg i.p.). DL-arginine showed neither inhibitory nor enhancing effects.

NG-hydroxymethyl arginine (400 mg/kg i.p. daily for 10 days) caused complete inhibition of Ehrlich ascites tumour growth in Swiss mice. In C57B1 mice with Lewis lung tumour, NG-hydroxymethyl arginine treatment reduced average lung metastasis number from 54 to 27 and average nodule volume from 50 mm³ to 34 mm³. In cell cultures, NG-hydroxymethyl arginine dose-dependently inhibited proliferation of HT-29, P-388, PC-3, and K-562 cells and induced morphological signs of apoptosis. Formaldehyde at concentrations of 1–10 μg/ml induced apoptosis in cell cultures, while 0.1–0.01 μg/ml stimulated DNA synthesis and cell proliferation.

**Clinical Implications** The review suggests that arginine deprivation or administration of D-arginine may retard tumour growth in humans. Methylated and hydroxymethylated arginine derivatives, which act as formaldehyde generators, represent a potential therapeutic approach for inducing tumour cell death or preventing proliferation. The authors note that arginine functions as a formaldehyde capturer, carrier, and generator molecule in biological systems, and this mechanism may underlie the biological activity of arginine derivatives. The clinical significance of the Arg 72-p53 genotype remains uncertain, with conflicting reports on its association with cervical cancer risk. The authors call for further studies on the possible application of arginine and its methylated derivatives in chemoprevention and cancer therapy.