Imatinib mesylate inhibits proliferation and modulates cytokine expression of human cancer-associated stromal fibroblasts from colorectal metastases.

Recent data have expanded the concept that cancer-associated stromal fibroblasts (CAFs) play an important role in tumor invasion and angiogenesis. Here, we show that platelet-derived growth factor (PDGF) is a mitogen for human CAFs isolated from hepatic metastases of colorectal cancer. The tyrosine kinase inhibitor imatinib mesylate (1 microM) abrogated the PDGF-induced DNA synthesis, and furthermore counteracted an inhibitory effect of PDGF on the expression of alpha-smooth muscle actin (alpha-SMA). High-dose imatinib mesylate (10 microM) decreased the viability of CAFs in vitro independent from co-stimulation with PDGF. Interestingly, imatinib mesylate (10 microM) strikingly induced the expression of the pro-inflammatory and pro-angiogenic cytokines interleukin (IL)-6 and IL-8, and mildly stimulated the release of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Our results suggest that imatinib mesylate, due to its anti-proliferative activity, may be effective in combination with other substances for the treatment of colorectal metastasis progression.

Intragraft iNOS induction during human liver allograft rejection depresses cytochrome p450 activity.

Allograft function may become impaired during rejection after human liver transplantation. Cytokines induce nitric oxide (NO) production in hepatocytes, Kupffer cells and infiltrating mononuclear cells. NO inhibits cytoplasmatic cytochrome p450 (CYP) enzyme activity in vitro. It is not known whether this mechanism plays a role in vivo. In order to characterize the role of locally produced cytokines in the pathogenesis of liver dysfunction, we analysed human liver transplant biopsy material for the expression of proinflammatory cytokines as well as for NO synthase and we compared these results to the microsomal liver function in vivo [aminopyrine breath test (ABT)] and in vitro (enzymatic analysis of CYP). Microsomal liver function decreased in vivo during rejection while ABT levels decreased by 40% and increased again by 59% after the acute rejection episode. Similarly, CYP 1A2 and 2E1 activity dropped 42% and 24% in rejecting samples, respectively. Competitive reverse transcriptase polymerase chain reaction (RT-PCR) showed a fivefold upregulation of interferon gamma (IFN-gamma) gene expression. Inducible, but not constitutive NO-synthase gene expression was upregulated fivefold in samples from rejecting patients suggesting a local induction of NO in response to immune events. Our data show a marked impairment of CYP enzyme activity during allograft rejection which is presumably secondary to an increased intragraft production of proinflammatory cytokines and NO.