Abstract
BackgroundChemotherapeutic drugs like Adriamycin (ADR) induces apoptosis or senescence in cancer cells but these cells often develop resistance and generate responses of short duration or complete failure. The methylxantine drug Pentoxifylline (PTX) used routinely in the clinics setting for circulatory diseases has been recently described to have antitumor properties. We evaluated whether pretreatment with PTX modifies apoptosis and senescence induced by ADR in cervix cancer cells.MethodsHeLa (HPV 18+), SiHa (HPV 16+) cervix cancer cells and non-tumorigenic immortalized HaCaT cells (control) were treated with PTX, ADR or PTX + ADR. The cellular toxicity of PTX and survival fraction were determinated by WST-1 and clonogenic assay respectively. Apoptosis, caspase activation and ADR efflux rate were measured by flow cytometry, senescence by microscopy. IκBα and DNA fragmentation were determinated by ELISA. Proapoptotic, antiapoptotic and senescence genes, as well as HPV-E6/E7 mRNA expression, were detected by time real RT-PCR. p53 protein levels were assayed by Western blot.ResultsPTX is toxic (WST-1), affects survival (clonogenic assay) and induces apoptosis in cervix cancer cells. Additionally, the combination of this drug with ADR diminished the survival fraction and significantly increased apoptosis of HeLa and SiHa cervix cancer cells. Treatments were less effective in HaCaT cells. We found caspase participation in the induction of apoptosis by PTX, ADR or its combination. Surprisingly, in spite of the antitumor activity displayed by PTX, our results indicate that methylxantine, per se does not induce senescence; however it inhibits senescence induced by ADR and at the same time increases apoptosis. PTX elevates IκBα levels. Such sensitization is achieved through the up-regulation of proapoptotic factors such as caspase and bcl family gene expression. PTX and PTX + ADR also decrease E6 and E7 expression in SiHa cells, but not in HeLa cells. p53 was detected only in SiHa cells treated with ADR.ConclusionPTX is a good inducer of apoptosis but does not induce senescence. Furthermore, PTX reduced the ADR-induced senescence and increased apoptosis in cervix cancer cells.
Highlights
Chemotherapeutic drugs like Adriamycin (ADR) induces apoptosis or senescence in cancer cells but these cells often develop resistance and generate responses of short duration or complete failure
Cell viability of human cervix cancer cells after in vitro treatment with PTX or ADR either alone or in combination We first evaluated cell sensitivity of HeLa, SiHa and HaCaT cells to in vitro treatment with either PTX alone or in combination with ADR, cell viability was determined in function of its metabolic activity by WST-1 assay
Cells treated with PTX, had viability of 63.6 ± 2.1% in HeLa cells, 57.8 ± 1.0% in SiHa cells and 74.1 ± 1.0% in HaCaT cells
Summary
Chemotherapeutic drugs like Adriamycin (ADR) induces apoptosis or senescence in cancer cells but these cells often develop resistance and generate responses of short duration or complete failure. The first one occurs during normal or physiological conditions or by stimuli such as chemotherapy and constitutes a common pathway for cell replacement, tissue remodeling, damaged cell removal and elimination of cancer cells [4,5,6] It is a complex process which involves caspases participation, activation of proapoptotic genes, among other molecules. Now is considered a general biological program of terminal growth arrest, and can be induced by the shortening of telomeres (growing old) or by injuries to DNA which do not involve telomere shortening (accelerated senescence) [9,10] In this state, while they may remain metabolically active, cells can not divide even if they are stimulated by mitogens. Recent data suggest that it facilitates cancer progression [9,10,11]
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