Browsing by Author "Pljesa, Igor (57194182186)"

Chemotherapy resistance of ovarian cancer, regarded as the most lethal malignant gynecological disease, can be explained by several mechanisms, including increased activity of efflux transporters leading to decreased intracellular drug accumulation, increased efflux of the therapeutic agents from the cell by multidrug-resistance-associated protein (MRP1), enhanced DNA repair, altered apoptotic pathways, silencing of a number of genes, as well as drug inactivation, especially by glutathione transferase P1 (GSTP1). Indeed, GSTP1 has been recognized as the major enzyme responsible for the conversion of drugs most commonly used to treat metastatic ovarian cancer into less effective forms. Furthermore, GSTP1 may even be responsible for chemoresistance of non-GST substrate drugs by mechanisms such as interaction with efflux transporters or different signaling molecules involved in regulation of apoptosis. Recently, microRNAs (miRNAs) have been identified as important gene regulators in ovarian cancer, which are able to target GST-mediated drug metabolism in order to regulate drug resistance. So far, miR-186 and miR-133b have been associated with reduced ovarian cancer drug resistance by silencing the expression of the drug-resistance-related proteins, GSTP1 and MDR1. Unfortunately, sometimes miRNAs might even enhance the drug resistance in ovarian cancer, as shown for miR-130b. Therefore, chemoresistance in ovarian cancer treatment represents a very complex process, but strategies that influence GSTP1 expression in ovarian cancer as a therapeutic target, as well as miRNAs affecting GSTP1 expression, seem to represent promising predictors of chemotherapeutic response in ovarian cancer, while at the same time represent potential targets to overcome chemoresistance in the future.

Purpose: Since several studies have proposed that epithelial ovarian cancer should not be considered as a single disease entity and that it results from an accumulation of genetic changes, we aimed to assess the polymorphic expression of major cytosolic glutathione S-transferases (GSTM1, T1, A1 and P1) with respect to ovarian cancer susceptibility and aggressiveness. Methods: This case-control study was conducted on 93 newly diagnosed epithelial ovarian cancer patients and 178 healthy matched controls. The multiplex polymerase chain reaction (PCR) was used to detect homozygous deletions ofGSTMl and GSTT1 genes. Analysis of the single nucleotide polymorphism (SNP) GSTA1 C69T was performed using PCR-restrictionfragment length polymorphism (RFLP), while for SNP GSTP1 Ile105Val real-time PCR was used. Results: No significant association to ovarian cancer risk was found for individual GSTM1, GSTA1 and GSTP1 genotypes (p>0.05). However, the carriers of GSTT1-active genotype were at 2-fold higher risk of ovarian cancer development (95%C1: 1.00-4.01, p=0.049), which was even more elevated in the subgroup of patients with positive family history of cancer. Moreover, the frequency of all three GST genotypes that might be associated to ovarian cancer risk (GSTT1-active, GSTA1-active and GSTPl-referent) was significantly higher in patients than in the control group (p=0.042). Even more, patients who were carriers of combination of these three genotypes represented over 64% of the total number of patients within any of the International Federation of Gynecology and Obstetrics (FIGO) stages of ovarian cancer. Conclusions: This study provides supportive evidence that GSTs might affect both susceptibility and progression of ovarian cancer.

Purpose: Since several studies have proposed that epithelial ovarian cancer should not be considered as a single disease entity and that it results from an accumulation of genetic changes, we aimed to assess the polymorphic expression of major cytosolic glutathione S-transferases (GSTM1, T1, A1 and P1) with respect to ovarian cancer susceptibility and aggressiveness. Methods: This case-control study was conducted on 93 newly diagnosed epithelial ovarian cancer patients and 178 healthy matched controls. The multiplex polymerase chain reaction (PCR) was used to detect homozygous deletions ofGSTMl and GSTT1 genes. Analysis of the single nucleotide polymorphism (SNP) GSTA1 C69T was performed using PCR-restrictionfragment length polymorphism (RFLP), while for SNP GSTP1 Ile105Val real-time PCR was used. Results: No significant association to ovarian cancer risk was found for individual GSTM1, GSTA1 and GSTP1 genotypes (p>0.05). However, the carriers of GSTT1-active genotype were at 2-fold higher risk of ovarian cancer development (95%C1: 1.00-4.01, p=0.049), which was even more elevated in the subgroup of patients with positive family history of cancer. Moreover, the frequency of all three GST genotypes that might be associated to ovarian cancer risk (GSTT1-active, GSTA1-active and GSTPl-referent) was significantly higher in patients than in the control group (p=0.042). Even more, patients who were carriers of combination of these three genotypes represented over 64% of the total number of patients within any of the International Federation of Gynecology and Obstetrics (FIGO) stages of ovarian cancer. Conclusions: This study provides supportive evidence that GSTs might affect both susceptibility and progression of ovarian cancer.