MRE11A and SKP2 genes are associated with the increased cytotoxicity induced by the synergistic effects of cisplatin and gemcitabine in bladder cancer cells.

The combination of gemcitabine and cisplatin has been shown previously to elicit a synergistic therapeutic effect on bladder cancer cell lines and result in reduced cell survival. However, the precise mechanism by which cells die has not been elucidated. Cell cycle-related genes are the predominant targets of chemotherapeutic protocols. Therefore, molecular biomarkers that are predictive of therapeutic outcomes associated with tumor sensitivity might be important for optimal treatment protocol selection. The aim of this study was to investigate the changes in gene expression in cell cycle-related genes that were induced by cisplatin, gemcitabine or a combined treatment using both agents in a low-grade urinary bladder transitional carcinoma cell line (RT4). The following three treatment protocols were used: 1.0 µM cisplatin, 1.56 µM gemcitabine and a combination of 1.0 µM cisplatin and 1.56 µM gemcitabine. Cytometry and morphology analysis (by phase-contrast photomicrography) were performed in addition to pathway-specific gene expression analysis using quantitative RT-PCR gene arrays. The following results were observed after 1.0 µM cisplatin treatment: (1) a decrease in cell number, (2) an increased percentage of scattered cells and (3) downregulated expression of genes related to cell cycle arrest, G1/S-to-mitotic cell cycle transition, DNA repair, apoptosis, transcription and mitosis. Treatment with 1.56 µM gemcitabine, or with both drugs simultaneously, induced the following effects: (1) a decrease in cell number, (2) an increased percentage of scattered and elongated cells, (3) the modulation of genes that are predominantly involved in DNA repair and (4) a significant upregulation of genes related to cell cycle arrest. Reduced cell density was observed after the combined treatment compared to the two other single-agent protocols. The downregulation of MRE11A and SKP2 was observed only in cells subjected to the combined treatment. In conclusion, cisplatin, gemcitabine and the combination of both drugs elicited distinct toxicogenomic effects in the RT4 bladder transitional carcinoma cell line, although disruptions in the expression of cell cycle control-related genes and other pathways responsible for cell survival were observed for all of the protocols. MRE11A and SKP2 downregulation appeared to be responsible for the synergistic therapeutic effects elicited by cisplatin and gemcitabine.

Cell cycle kinetics, apoptosis rates, DNA damage and TP53 gene expression in bladder cancer cells treated with allyl isothiocyanate (mustard essential oil).

Allyl isothiocyanate (AITC) is present in plants of the cruciferous family and is abundant in mustard seed. Due to its high bioavailability in urine after ingestion, AITC has been considered a promising antineoplastic agent against bladder cancer. Because TP53 mutations are the most common alterations in bladder cancer cells and are frequently detected in in situ carcinomas, in this study, we investigated whether the AITC effects in bladder cancer cells are dependent on the TP53 status. Two bladder transitional carcinoma cell lines were used: RT4, with wild-type TP53; and T24, mutated TP53 gene. AITC was tested at concentrations of 0.005, 0.0625, 0.0725, 0.0825, 0.0925, 0.125 and 0.25 µM in cytotoxicity, cell and clonogenic survival assays, comet and micronucleus assays and for its effects on cell cycle and apoptosis by flow cytometry and on TP53 gene expression. The data showed increased primary DNA damage in both cell lines; however, lower concentrations of AITC were able to induce genotoxicity in the mutant cells for the TP53 gene. Furthermore, the results demonstrated increased apoptosis and necrosis rates in the wild-type cells, but not in mutated TP53 cells, and cell cycle arrest in the G2 phase for mutated cells after AITC treatment. No significant differences were detected in TP53 gene expression in the two cell lines. In conclusion, AITC caused cell cycle arrest, increased apoptosis rates and varying genotoxicity dependent on the TP53 status. However, we cannot rule out the possibility that those differences could reflect other intrinsic genetic alterations in the examined cell lines, which may also carry mutations in genes other than TP53. Therefore, further studies using other molecular targets need to be performed to better understand the mechanisms by which AITC may exert its antineoplastic properties against tumor cells.

Toxicogenomic activity of gemcitabine in two TP53-mutated bladder cancer cell lines: special focus on cell cycle-related genes.

Because of its lower toxicity and good tolerability and response, gemcitabine has been described as one of the most highly promising drugs for urinary bladder cancer therapy. Its phosphorylated active-dFdCTP metabolite can incorporate into DNA, causing replication blockage. Additionally, it is known that mutations in the TP53 gene are related to the high recurrence rate of these neoplasias. Based on these premises, we investigated the effects of gemcitabine on the expression of the cell cycle-related genes in two different TP53-mutated bladder transitional carcinoma cell lines-5637 (from a moderate-grade tumor with a TP53 allele carrying two mutations) and T24 (from an invasive tumor with a TP53 allele encoding an in-frame deletion). Cell viability and morphology analyses (phase-contrast photomicrographs), Nuclear Division Index and pathway-specific quantitative RT-PCR gene arrays were performed. Treatment with gemcitabine led to the following results: (1) a significant decrease of viable T24 cells after treatment at the highest concentration (3.12 µM) tested; (2) scattered, elongated and vacuolated 5637 and T24 cells; (3) a cytostatic effect in both cell lines; and (4) significant upregulation of the BRCA1, CCNE1, CDK2, CDK6, CDKN1A, CDKN2B, E2F4, GADD45A, MAD2L2, CCNH, SERTAD1, CDC1, and CHEK1 genes. Gemcitabine had distinct toxicogenomic effects in the bladder transitional carcinoma cell lines with two different TP53 mutations. However, independent of the type of mutation and tumor grade, gemcitabine induced cell cycle arrest; upregulation of DNA repair-related genes, G1/S transition, apoptosis and activation of transcription factors, mainly by upregulation of the CCNE1, CDKN1A and GADD45A genes.

In vivo and in vitro analysis of cytogenotoxicity in populations living in abnormal conditions from Santos-Sao Vicente estuary.

The aim of the study was to evaluate cyto- and genotoxic effects in populations living in subnormal clusters in Santos São Vicente estuary. For in vivo study, samples of buccal mucosa and peripheral blood cells were collected. Micronucleus assay and single-cell gel (comet) assay were performed. For in vitro study, Chinese ovary hamster (CHO) cells were exposed to contaminated water. The results showed that people living in the contaminated estuary have increased DNA damage in oral mucosa and peripheral blood cells, as detected in the micronucleus and comet assays respectively. In addition, estuarine water was able to promote cytotoxicity at the highest concentrations, as well as decrease the number of cells in the G1 phase. In summary, our results indicate that water from the Santos-São Vicente estuary is capable of inducing cytogenotoxicity in mammalian cells in vivo and in vitro.

Antiproliferative activity of goniothalamin enantiomers involves DNA damage, cell cycle arrest and apoptosis induction in MCF-7 and HB4a cells.

(R)-goniothalamin (R-GNT) is a styryl lactone that exhibits antiproliferative property against several tumor cell lines. (S)-goniothalamin (S-GNT) is the synthetic enantiomer of R-GNT, and their biological properties are poorly understood. The aim of this study was to evaluate the antiproliferative mechanisms of (R)-goniothalamin and (S)-goniothalamin in MCF-7 breast cancer cells and HB4a epithelial mammary cells. To determine the mechanisms of cell growth inhibition, we analyzed the ability of R-GNT and S-GNT to induce DNA damage, cell cycle arrest and apoptosis. Moreover, the gene expression of cell cycle components, including cyclin, CDKs and CKIs, as well as of genes involved in apoptosis and the DNA damage response were evaluated. The natural enantiomer R-GNT proved more effective in both cell lines than did the synthetic enantiomer S-GNT, inhibiting cell proliferation via cell cycle arrest and apoptosis induction, likely in response to DNA damage. The cell cycle inhibition caused by R-GNT was mediated through the upregulation of CIP/KIP cyclin-kinase inhibitors and through the downregulation of cyclins and CDKs. S-GNT, in turn, was able to cause G0/G1 cell cycle arrest and DNA damage in MCF-7 cells and apoptosis induction only in HB4a cells. Therefore, goniothalamin presents potent antiproliferative activity to breast cancer cells MCF-7. However, exposure to goniothalamin brings some undesirable effects to non-tumor cells HB4a, including genotoxicity and apoptosis induction.

Cell cycle arrest and apoptosis in TP53 subtypes of bladder carcinoma cell lines treated with cisplatin and gemcitabine.

Currently, the combination of cisplatin and gemcitabine is considered a standard chemotherapeutic protocol for bladder cancer. However, the mechanism by which these drugs act on tumor cells is not completely understood. The aim of the present study was to investigate the effects of these two antineoplastic drugs on the apoptotic index and cell cycle kinetics of urinary bladder transitional carcinoma cell lines with wild-type or mutant TP53 (RT4: wild type for TP53; 5637 and T24: mutated TP53). Cytotoxicity, cell survival assays, clonogenic survival assays and flow cytometric analyses for cell cycle kinetics and apoptosis detection were performed with three cell lines treated with different concentrations of cisplatin and gemcitabine. G(1) cell cycle arrest was observed in the three cell lines after treatment with gemcitabine and gemcitabine plus cisplatin. A significant increase in cell death was also detected in all cell lines treated with cisplatin or gemcitabine. Lower survival rates occurred with the combined drug protocol independent of TP53 status. TP53-wild type cells (RT4) were more sensitive to apoptosis than were mutated TP53 cells when treated with cisplatin or gemcitabine. Concurrent treatment with cisplatin and gemcitabine was more effective on transitional carcinoma cell lines than either drug alone; the drug combination led to a decreased cell survival that was independent of TP53 status. Therefore, the synergy between low concentrations of cisplatin and gemcitabine may have clinical relevance, as high concentrations of each individual drug are toxic to whole organisms.