Pentoxifylline promotes development of murine colon adenocarcinoma-derived metastatic tumors in liver.

Pentoxifylline is commonly used in the treatment of peripheral vascular diseases. It improves microcirculatory flow and tissue perfusion. Moreover, pentoxifylline displays some immunomodulatory properties that presumably might affect the anticancer response. Therefore, the aim of the present study was to evaluate the influence of pentoxifylline on tumor development. Balb/c mice were injected with murine colon adenocarcinoma C-26 cells intravenously, into the vena portae, and divided into two groups. Mice from the experimental groups received daily intraperitoneal injections of pentoxifylline (30 mg/kg) while the controls were injected with 0.9% NaCl. Two weeks after C-26 cell inoculation mice were sacrificed and autopsy was performed. It was found that the livers of control animals revealed only several small tumor foci, whereas the livers of pentoxifylline-treated mice displayed numerous cancerous outgrowths. The mean liver weight in pentoxifylline group was 2.21+/-0.62 g as compared to 1.36+/-0.15 g in controls (P=0.004). Moreover, the influence of pentoxifylline on murine and human cell line proliferation in vitro was evaluated. It has been observed that pentoxifylline, at pharmacologically achievable concentrations, stimulated the proliferation of murine (C-26) and human (CaSki, U-937) cell lines. However, it did not stimulate human melanoma (WM-35) cell proliferation. Since there has been no evidence so far that pentoxifylline may promote tumor progression, it is still considered to be a safe drug. Moreover, some beneficial properties of pentoxifylline, which could be useful in cancer treatment, have been reported and a few clinical trials with oncological patients have been performed. Surprisingly, our study revealed that pentoxifylline significantly promoted C-26-derived metastatic tumor growth in liver. Although this model might be unique in its sensitivity to tumor-promoting effects of pentoxifylline, it cannot be excluded that similar effects might occur in some cases of tumors developing in humans. Such effects could be relevant, since the stimulatory influence of pentoxifylline on proliferation does not appear to be species- or tissue-specific.