Inhibition of endothelial cell proliferation and tumor-induced angiogenesis by pentoxifylline.

PURPOSE: In this study we investigated the effect of pentoxifylline (PTX) on tumor-induced neovascularization as well as on different steps involved in the angiogenic process. METHODS: To assess angiogenesis inhibition. we injected intradermally (i.d.) 10 B16-F10 melanoma cells into C57BL/6J mice which were subsequently intraperitoneally (i.p.) inoculated with PTX or saline. On day 7 the number of blood vessels converging to the remnant of injected material was counted and the volumes of incipient tumors were calculated in each case. In vitro growth inhibition by PTX was evaluated in two different cell lines of endothelial origin and in human umbilical vein endothelial cells. Motility assays, as well as zymographic assays carried out to analyze gelatinolytic metalloproteinases and urokinase-type plasminogen activator, were performed in one of the endothelial cell lines. RESULTS: A significant inhibition of tumor-induced angiogenesis was observed in C57B1/6 mice i.p. inoculated with PTX, that paralleled reduced incipient tumor volumes. The endothelial cells derived from different sources were inhibited in a dose-response manner by PTX in vitro. Non-cytotoxic PTX concentrations assayed in one of the endothelial cell lines did not inhibit its in vitro cell motility nor its gelatinase secretion, but its low molecular weight urokinase-type plasminogen activator expression. CONCLUSIONS: Our findings suggest that the inhibitory effect of PTX on tumor angiogenesis is related to antiproliferative action on endothelial cells, as well as to down regulation of u-PA secreted by them.

Differential anthracycline sensitivity in two related human colon carcinoma cell lines expressing similar levels of P-glycoprotein.

Chemosensitivity of the human colon carcinoma HCT-15 cell line to 4'-epidoxorubicin proved to be 100-fold higher than that of its variant HCT-15 EDR. Confocal scanning microscopy showed significant less drug accumulation in HCT-15 EDR. A 2-fold increase in hsp27 expression was found in HCT-15 EDR, with no alteration in hsp70. The expression of the drug exporter Pgp was similar in both cell lines, despite the lower drug accumulation shown by HCT-15 EDR in respect to HCT-15. Other molecules implicated in the acquisition of enhanced chemoresistance or a more active Pgp variant present in HCT-15 EDR, could explain the phenomenon.

[Molecular characteristics of RB1 tumor suppressor gene]. / Características moleculares del gen supresor tumoral RB1.

RB1 tumor suppressor gene is implicated in the development of some malignancies, among which retinoblastoma is the most common; in this tumor RB1 gene is generally deleted. This gene is closely associated to the cell cycle regulation and it constitutes a molecular binding target of viral oncoproteins, which inhibits its protein product, thus interrupting cell cycle progression. This paper describes its molecular features, in order to identify its mutations.