Bulent Karabulut

Docetaxel/zoledronic acid combination triggers apoptosis synergistically through downregulating antiapoptotic Bcl-2 protein level in hormone-refractory prostate cancer cells.

Docetaxel, a semi‐synthetic taxane analogue, is used effectively in the treatment of metastatic prostate cancer. Zoledronic acid, the most potent member of bisphosphonates, has shown pleiotropic anti‐tumoral effects on prostate cancer cells. We have explored the possible additive/synergistic effects and the apoptotic pathways induced by combination treatment of docetaxel and zoledronic acid in hormone and drug refractory, PC‐3 and DU‐145 prostate cancer cells. Combination of docetaxel and zoledronic acid synergistically inhibits cell growth in PC‐3 and DU‐145 cells. Moreover, this effect was due to downregulation of antiapoptotic protein Bcl‐2 in PC‐3 and DU‐145 cells. In conclusion, docetaxel/zoledronic acid combination is potentially a novel and effective approach for the treatment of prostate cancer.

Gemcitabine treatment in patients with inoperable locally advanced/metastatic pancreatic cancer and prognostic factors

Objective. Most patients with pancreatic cancer show an inoperable locally advanced/ metastatic tumour at the time of diagnosis. The present study was aimed at determining the prognostic factors in patients with advanced pancreatic carcinoma treated with gemcitabine. Material and methods. Sixty-seven unresectable or metastatic pancreatic cancer patients treated with gemcitabine were included in the study and a total of 258 cycles of treatment were applied. Results. The overall response rate was 5%. Thirty-one percent of the patients had stable disease, whereas progressive disease was seen in 49%. Clinical benefit response rate was 15%. The median duration of response was 7.3 months. Median progression-free survival was 3 months, while median overall survival was 9 months. Univariate analysis revealed that worse results were found in patients with performance status (PS) = 2, and in patients with primary tumour location in the body or tail of the pancreas (p<0.05). Multivariate analysis of data revealed that the most important factor was PS of the patient, as the patients with PS = 2 had worse results than the patients with PS = 0–1 (p<0.05). Conclusions. Low PS is a negative predictive factor for the survival of patients with advanced pancreatic carcinoma treated with gemcitabine.

Overcoming drug resistance in hormone- and drug-refractory prostate cancer cell line, PC-3 by docetaxel and gossypol combination.

Drug resistance is a significant challenge of daily oncology practice. Docetaxel and gossypol both have antitumoral activity in hormone-refractory prostate cancer (HRPC). Our results revealed that docetaxel and gossypol were synergistically cytotoxic and apoptotic in PC-3 cells in a dose- and time-dependent manner. We further investigated the expression profiles of genes involved in drug resistance and metabolism with a Human Cancer Drug Resistance and Metabolism PCR Array® (SuperArray). Six of the 84 genes that are known to regulate drug resistance, metabolism, cell cycle, DNA repair and oncogenesis were downregulated ≥3-fold change by the combination treatment. These results may be important in devising mechanism-based and targeted therapeutic strategies for prostate cancer, especially in devising combination therapy for drug resistant prostate cancers.

Enhancement of docetaxel-induced cytotoxicity and apoptosis by all-trans retinoic acid (ATRA) through downregulation of survivin (BIRC5), MCL-1 and LTbeta-R in hormone- and drug resistant prostate cancer cell line, DU-145

BackgroundThe management of hormone-refractory prostate cancer (HRPC) still remains as an important challenge of daily oncology practice. Docetaxel has proved to be a first line treatment choice. All-trans retinoic acid (ATRA) could potently inhibit the growth of prostate cancer cells in vitro and its combination with various anticancer agents results in increased cytotoxicity. Based on these data, our aim was to examine the synergistic/additive cytotoxic and apoptotic effects of combination of docetaxel and ATRA, in hormone- and drug refractory human DU-145 prostate cancer cells. Furthermore, we have searched for the underlying mechanisms of apoptosis by demonstrating apoptosis-related genes.MethodsXTT cell proliferation assay was used for showing cytotoxicity. For verifying apoptosis, both DNA Fragmentation by ELISA assay and caspase 3/7 activity measurement were used. For detecting the mechanism of apoptosis induced by docetaxel-ATRA combination, OligoGeArray® which consists of 112 apoptosis related genes was used.ResultsOur results revealed that docetaxel and ATRA were synergistically cytotoxic and apoptotic in DU-145 cells, in a dose- and time dependent manner. It was also shown by our studies that apoptosis was induced in DU-145 prostate carcinoma cells with significant cytotoxicity, no matter which agent applied first. We have found out that docetaxel-ATRA combination significantly downregulates survivin (BIRC5), myeloid cell leukemia-1 (MCL-1) and lymphotoxin β-receptor (LTβR) genes, which all three have pivotal roles in regulation of apoptosis and cell cycle progression.ConclusionIn conclusion, we strongly suggest that docetaxel and ATRA combination is a good candidate for this challenging era of daily oncologic practice. Also, the combination of docetaxel and ATRA might allow a reduction in docetaxel doses and by this way may diminish docetaxel adverse effects while maintaining the therapeutic effect in patients with HRPC.

Gemcitabine and vinorelbine combination in patients with metastatic breast cancer.

Both gemcitabine and vinorelbine as single agents have significant activity against metastatic breast cancer, with an overall response rate ranging from 14% to 40%. Because each drug has different mechanisms of action and toxicity profile, we have evaluated the activity and tolerability as a combined regimen in metastatic breast cancer patients. Thirty‐two breast cancer patients with prior chemotherapy for metastatic disease received a combination of gemcitabine and vinorelbine at 1,200 and 30 mg/m 2, respectively. The drugs were administered on days 1 and 8 of every 21‐day cycle. The study was designed to evaluate the response rate, the duration of response, the time to progression, and overall survival. Toxicity and tolerability of this combination were also evaluated. Out of 32 patients analyzed, a complete response was achieved in 2 patients (6.3%) and a partial response in 12 patients (37.5%), with an overall response rate of 43.8%. After a median follow‐up of 7 months, the median duration of response was 5.3 months, and the time to progression was 5.0 months. Overall survival was not reached because the majority of the patients were alive at the time of analysis. The gemcitabine and vinorelbine combination was tolerable, with hematologic toxicity being the most common side‐effect. Three patients suffered from grade 4 neutropenia, and none suffered from grade 4 thrombocytopenia. Nonhematologic toxicity was minimal and transient, with nausea and phlebitis being the most common. The gemcitabine and vinorelbine combination at the previously specified doses shows significant activity in metastatic breast cancer patients. The treatment is well tolerated and has an acceptable toxicity profile. In patients previously treated with anthracyclines and taxanes, this combination regimen offers an alternative treatment with preservation of a good quality of life.

Controlled Release of Methotrexate from W/O Microemulsion and Its In Vitro Antitumor Activity

The objective of this study was to prepare the microemulsion of methotrexate (M-MTX) for oral use and to investigate the suppressive effect of MTX-loaded microemulsion on MCF-7 human breast cancer cells. At the same time this effect of M-MTX was compared with those of a solution of the drug (Sol-MTX). Microemulsion was composed of soybean oil as oil phase, a mixture of Cremophore EL and Span 80 as surfactants, and isopropyl alcohol as co-surfactant, and 0.2 N NaOH as the aqueous phase. MTX was added into microemulsion at the last stage. We clearly demonstrated that M-MTX had a significant cytotoxic effect on breast cancer cell lines and the cytotoxic effect of M-MTX was significantly more than that of solutions (p < 0.05) and IC50 value for M-MTX was 40 ng/mL. We also examined M-MTX and Sol-MTX on a model biological environmental model. For this purpose a gastrointestinal cell culture model, the Caco-2 cell line, was used to investigate the cytotoxic effects of the polymeric carrier and its effect on the cell monolayer integrity. The differences between the viability of cells for M-MTX and Sol-MTX were significantly different when applied to ANOVA according to 2 × 8 factorial randomized design (p:0.016; for α: 0.05, power : 0.695). According to the in vitro cytotoxicity studies, we concluded that when MTX was incorporated into the microemulsion (M-MTX), which is a new drug carrier system, it suppresses tumour cell growth on multiple tumor lines. These results indicate that M-MTX may exert a low cytotoxic effect on normal cells and may be effective as an antitumor agent that induces apoptosis.

Regulation of growth factors in hormone- and drug-resistant prostate cancer cells by synergistic combination of docetaxel and octreotide.

To evaluate the effects of combined treatment with docetaxel and octreotide, a somatostatin analogue, on human hormone‐ and drug‐refractory prostate cancer cell lines, PC‐3 and DU‐145, and on some growth factors related to tumour growth and angiogenesis in prostate cancer.

Potential Predictive Factors for Response to Weekly Paclitaxel Treatment in Patients with Metastatic Breast Cancer

Abstract The authors compare results obtained from weekly paclitaxel treatment in advanced breast cancer patients with biological and clinical prognostic factors. Expression of c-erbB-2, Ki-67, p53 and hormone receptors (HR) was examined by immunohistochemistry in samples of breast tissue from 30 patients. Univariate analysis showed that Ki-67 positivity and low performance status (PS) were associated with poor outcome (P <0.05). We observed that expression of p53 and c-erbB-2 did not have any negative effect on response to chemotherapy and survival. HR-negative patients had better response and slightly statistically significant overall survival (OS) rates compared to HR-positive patients (P >0.05). In a multivariate analysis low PS was the only significant predictor of shorter survival (P <0.05). In conclusion, while the expression of p53 and c-erbB-2 did not have any effect on treatment results, negative Ki-67 expression and negative HR status were associated with better OS in this patient population. PS was the only significant predictor for OS.

Combination of AT-101/cisplatin overcomes chemoresistance by inducing apoptosis and modulating epigenetics in human ovarian cancer cells

We investigated the effects of AT-101/cisplatin combination treatment on the expression levels of apoptotic proteins and epigenetic events such as DNA methyltransferase (DNMT) and histone deacetylase (HDAC) enzyme activities in OVCAR-3 and MDAH-2774 ovarian cancer cells. XTT cell viability assay was used to evaluate cytotoxicity. For showing apoptosis, both DNA Fragmentation and caspase 3/7 activity measurements were performed. The expression levels of apoptotic proteins were assessed by human apoptosis antibody array. DNMT and HDAC activities were evaluated by ELISA assay and mRNA levels of DNMT1 and HDAC1 genes were quantified by qRT-PCR. Combination of AT-101/cisplatin resulted in strong synergistic cytotoxicity and apoptosis in human ovarian cancer cells. Combination treatment reduced some pivotal anti-apoptotic proteins such as Bcl-2, HIF-1A, cIAP-1, XIAP in OVCAR-3 cells, whereas p21, Bcl-2, cIAP-1, HSP27, Clusterin and XIAP in MDAH-2774 cells. Among the pro-apoptotic proteins, Bad, Bax, Fas, phospho-p53 (S46), Cleaved caspase-3, SMAC/Diablo, TNFR1 and Cytochrome c were induced in OVCAR-3 cells, whereas, Bax, TRAILR2, FADD, p27, phospho-p53 (S46), Cleaved caspase-3, Cytochrome c, SMAC/Diablo and TNFR1 were induced in MDAH-2774 cells. Combination treatment also inhibited both DNMT and HDAC activities and also mRNA levels in both ovarian cancer cells. AT-101 exhibits great potential in sensitization of human ovarian cancer cells to cisplatin treatment in vitro, suggesting that the combination of AT-101 with cisplatin may hold great promise for development as a novel chemotherapeutic approach to overcome platinum-resistance in human ovarian cancer.

Pretreatment with AT-101 enhances tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis of breast cancer cells by inducing death receptors 4 and 5 protein levels

PurposeTumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily and has been shown to induce extrinsic pathway of apoptosis in many types of cancer cells. AT-101, an (−)-enantiomer of gossypol, is a potent anticancer agent that is shown to be an inhibitor of Bcl-2/Bcl-XL. In this study, we searched whether pretreatment with either of these drugs would result in the enhancement of apoptosis through induction of death receptors and activation of mitochondrial pathways within breast cancer cells.MethodsHuman breast cancer (MCF-7 and MDA-MB-231) and normal breast cells (MCF-10A) were treated with drugs alone/in combination/sequentially. XTT cell viability assay was used to evaluate cytotoxicity. For showing apoptosis, both DNA Fragmentation and caspase 3/7 activity measurements were done. ELISA and Western blot analysis were done to assess DR4 and DR5 protein levels. The expression levels of apoptotic proteins were assessed by human apoptosis antibody array.ResultsThe sequential treatment of AT-101 followed by TRAIL resulted in significant synergistic cytotoxicity and apoptosis. Moreover, pretreatment of breast cancer cells with AT-101 and then with TRAIL caused enhancement of the expression levels of DR4 and DR5 in both cancer cell lines, suggesting that these cells were under strong apoptotic stimuli.ConclusionsThese findings all together, strongly suggest that pretreatment with AT-101 enhances TRAIL-induced death-inducing signaling complex resulting in the engagement of the mitochondrial pathway to apoptosis in breast cancer cells. These promising, preliminary results make AT-101 and TRAIL a novel combination treatment candidate for breast cancer.