Hellinida Thomadaki

BCL2 Family of Apoptosis-Related Genes: Functions and Clinical Implications in Cancer

One of the most effective ways to combat different types of cancer is through early diagnosis and administration of effective treatment, followed by efficient monitoring that will allow physicians to detect relapsing disease and treat it at the earliest possible time. Apoptosis, a normal physiological form of cell death, is critically involved in the regulation of cellular homeostasis. Dysregulation of programmed cell death mechanisms plays an important role in the pathogenesis and progression of cancer as well as in the responses of tumours to therapeutic interventions. Many members of the BCL2 (B-cell CLL/lymphoma 2; Bcl-2) family of apoptosis-related genes have been found to be differentially expressed in various malignancies, and some are useful prognostic cancer biomarkers. We have recently cloned a new member of this family, BCL2L12, which was found to be differentially expressed in many tumours. Most of the BCL2 family genes have been found to play a central regulatory role in apoptosis induction. Results have made it clear that a number of coordinating alterations in the BCL2 family of genes must occur to inhibit apoptosis and provoke carcinogenesis in a wide variety of cancers. However, more research is required to increase our understanding of the extent to which and the mechanisms by which they are involved in cancer development, providing the basis for earlier and more accurate cancer diagnosis, prognosis and therapeutic intervention that targets the apoptosis pathways. In the present review, we describe current knowledge of the function and molecular characteristics of a series of classic but also newly discovered genes of the BCL2 family as well as their implications in cancer development, prognosis and treatment.

Cisplatin‐Induced Apoptosis in HL‐60 Human Promyelocytic Leukemia Cells

Abstract: The anti‐apoptotic molecule BCL2 delays cell‐cycle entry from quiescence. We have recently cloned a new member of the BCL2 family of apoptosis‐related genes, BCL2L12. In the present study, the expression of BCL2 and BCL2L12 genes during cisplatin‐induced apoptosis in HL‐60 leukemic cells was investigated. The kinetics of apoptosis induction and cell toxicity were evaluated by DNA laddering and the MTT method, respectively. BCL2 and BCL2L12 expression was analyzed by RT‐PCR using gene‐specific primers. The ratio of apoptotic cells increased with increasing concentrations of cisplatin and exposure time of cell culture to the drug. Gradual, time‐dependent downregulation of BCL2 gene was observed during cisplatin treatment. Up‐regulation of BCL2L12 was observed 3 h (no DNA fragmentation) and 6 h (initiation of the DNA fragmentation) after treatment with cisplatin, followed by a decrease of its expression after 12‐h continuous treatment with the drug. It is known that the main anti‐carcinogenic effect of cisplatin is due to the induction of cell apoptosis. Present results indicate that downregulation of the BCL2 and upregulation of the BCL2L12 gene may be the underlying mechanisms.

The role of cordycepin in cancer treatment via induction or inhibition of apoptosis: implication of polyadenylation in a cell type specific manner

PurposeMost anticancer drugs show their antiproliferative and cytotoxic activity via induction of apoptosis. In the present study we assessed the implication and role of cordycepin, a polyadenylation-specific inhibitor and a well-known chemotherapeutic drug, in apoptosis, induced by the anticancer drug etoposide.MethodsFor this purpose, a variety of leukemia and lymphoma cell lines (U937, K562, HL-60, Daudi, Molt-4) were treated with the anticancer drugs etoposide and/or cordycepin and assessed for poly(A) polymerase (PAP) activity and isoforms by the highly sensitive PAP activity assay and western blotting, respectively. Induction of apoptosis was determined by endonucleosomal DNA cleavage, DAPI staining, caspase-6 activity assay and ΔΨm reduction, whereas cytotoxicity and cell cycle status were assessed by Trypan blue staining, MTT assay and flow cytometry.Results and conclusionsThe results showed that PAP changes in all cell lines, in response to apoptosis induced by etoposide, in many cases even prior to hallmarks of apoptosis (endonucleosomal cleavage of DNA, ΔΨm reduction). A further elucidation to this apoptosis–polyadenylation correlation was added, by cell treatment with cordycepin, resulting in either suppression (U937, K562) or induction (HL-60) of the apoptotic process, according to the cell type. However, inhibition of polyadenylation did not influence the cell lines Daudi and Molt-4 used, where alternative apoptotic pathways are induced through cleavage of DNA into high molecular weight fragments.

Polyadenylate polymerase modulations in human epithelioid cervix and breast cancer cell lines, treated with etoposide or cordycepin, follow cell cycle rather than apoptosis induction.

Abstract Cancer results from an imbalance between cell cycle progression and apoptosis. Therefore, most anticancer drugs exert their antiproliferative and cytotoxic activity via cell cycle arrest and induction of apoptosis, a controlled form of cell death that is dysregulated in cancer. Many polyadenylation trans-acting factors, including polyadenylate polymerase (PAP), are increasingly found to be involved in cell cycle, apoptosis and cancer prognosis. The objective of the present study was to identify PAP modulations in the response of two epithelial cancer cell lines (HeLa and MCF-7) to apoptosis induction by the anticancer drugs etoposide and cordycepin. Cells were assessed for PAP activity and isoforms by the highly sensitive PAP activity assay and Western blotting, respectively. Induction of apoptosis was determined by endonucleosomal DNA cleavage, 4′6-diamidino-2-phenylindol (DAPI) staining and caspase-6 activity assay, whereas cytotoxicity and cell cycle status were assessed by trypan blue staining, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. Our results indicate that PAP changes very early in response to either etoposide or cordycepin treatment, even prior to the hallmarks of apoptosis (chromatin condensation and cleavage), in both cell lines tested, but in a different mode. Our results suggest, for the first time, that in the epithelial cancer cell lines used, PAP modulations follow cell cycle progression rather than the course of apoptosis.

Alterations in mRNA expression of apoptosis-related genes BCL2, BAX, FAS, caspase-3, and the novel member BCL2L12 after treatment of human leukemic cell line HL60 with the antineoplastic agent etoposide.

Abstract:  Apoptotic cell death is a highly regulated process, which plays a crucial role in many biological events. Etoposide is an antineoplastic drug, which targets the DNA unwinding enzyme, topoisomerase II. The aim of the present research approach to investigate the expression of the apoptosis‐related genes BCL2 (Bcl‐2), FAS, Caspase‐3, BAX and the new member BCL2L12, cloned by our group, along with treatment of HL‐60 leukemia cells with etoposide. The kinetics of apoptosis induction and cell toxicity was evaluated by DNA laddering and MTT method, respectively. The mRNA expression levels of the genes were analyzed by RT‐PCR using gene‐specific primers. β‐Actin was used as a control gene. An important downregulation of BCL2L12 was observed at 4 h of drug treatment, whereas BAX was upregulated at the same time point. No alteration in the expression pattern of the other apoptosis‐related genes was detected. Since, the main anticarcinogenic effect of etoposide is due to the induction of apoptosis, these changes observed in the mRNA expression levels of the genes may be an underlying mechanism.

Breast cancer cells response to the antineoplastic agents cisplatin, carboplatin, and doxorubicin at the mRNA expression levels of distinct apoptosis-related genes, including the new member, BCL2L12.

Abstract:  Most apoptosis‐related genes regulate cellular fate as a response to anticancer drugs. Modulations at the mRNA levels of such genes often correlate with the sensitivity of various types of cancer cells to chemotherapeutic reagents. The drugs cisplatin, carboplatin, and doxorubicin exhibit anticancer activity, the mechanism of which is not yet completely clarified, although they are known to modulate the expression of several genes including apoptosis‐related genes, such as members of the BCL2 (Bcl‐2) family. In order to define the significance of the expression patterns of such genes as a response to anticancer drug cytotoxic activity, we studied the possible alterations in the mRNA expression levels of various apoptosis‐related genes, including the new member, BCL2L12, after cell treatment with distinct anticancer drugs (cisplatin, carboplatin, and doxorubicin), in the breast cancer cell line, MCF‐7. The kinetics of cell toxicity was evaluated by the MTT method, whereas the expression levels of distinct apoptosis‐related genes were analyzed by reverse transcriptase polymerase chain reaction (RT‐PCR), using gene‐specific primers. The percentage of nonviable cells was upregulated with increasing concentrations and cell exposure time to the different anticancer drugs. Distinct modulations of apoptosis‐related genes, at the mRNA level, were also observed. However, further work is required in order to ascertain whether the mRNA expression profile of such genes may provide evidence for their contribution to more specific and sensitive prediction of breast cancer response to treatment and therefore the rationale for individualized, more appropriate, and successful treatment.

mRNA expression analysis of a variety of apoptosis-related genes, including the novel gene of the BCL2-family, BCL2L12, in HL-60 leukemia cells after treatment with carboplatin and doxorubicin

Abstract Apoptosis is a type of programmed cell death involved in many crucial biological processes. It represents the basic mechanism for the action of chemotherapeutic agents, such as doxorubicin and carboplatin. Both are able to cause cell death through the induction of apoptosis in the human leukemic cell line HL-60. We investigated the possible alterations in the expression of apoptosis-related genes, including the novel BCL2L12 gene, which was recently cloned in our group. The kinetics of apoptosis induction and cell toxicity was investigated by DNA laddering and by the MTT method, respectively. Total RNA was extracted and cDNA was prepared by reverse transcription. BCL2, BAX, FAS, caspase-9, caspase-3 and BCL2L12 were amplified by PCR. Overexpression of FAS, BCL2L12 and caspase-3 was observed after treatment of HL-60 cells for 3 or 6 h with carboplatin, while their expression was decreased after a 12-h treatment, demonstrating that these genes may take part in the early stages of apoptosis. Overexpression of the same genes was also observed after 6 h of treatment with doxorubicin (concomitantly with DNA laddering). In the case of carboplatin-induced apoptosis we detected down-regulation of BAX, BCL2 and caspase-9, whereas in the case of doxorubicin, BAX and BCL2 remained at control levels and caspase-9 was increased.

Molecular profile of the BCL2 family of the apoptosis related genes in breast cancer cells after treatment with cytotoxic/cytostatic drugs.

BCL2 (bcl-2) gene family members are important regulators of apoptosis. Increasing evidence supports their modulated expression in breast cancer cells and in many cases their relation to chemotherapy response, outcome, and overall prognosis, as well as their value as important potent therapeutic targets. Investigation and increased understanding of their transcriptional regulation and their specific roles in cancer progression and therapy response will be useful for focusing research on the development of novel therapies targeted against this gene family members’ expression status. In the present review, we describe current knowledge of the molecular profile of the classical and novel members of the BCL2 family of genes as a response of breast cancer cells to cytotoxic/cytostatic drugs.

Treatment of MCF-7 cells with taxol and etoposide induces distinct alterations in the expression of apoptosis-related genes BCL2, BCL2L12, BAX, CASPASE-9 and FAS

Abstract We studied alterations in the mRNA expression levels of BCL2 (Bcl-2), BCL2L12, BAX, FAS and CASPASE-9 genes in the MCF-7 breast cancer cell line in response to treatment with two anticancer drugs. Cell toxicity was evaluated by the MTT method, trypan blue staining and DNA laddering, whereas the expression levels of the apoptosis-related genes were analysed by RT-PCR using gene-specific primers. In the case of etoposide, down-regulation of the BCL2L12-A gene variant and of CASPASE-9, as well as upregulation of BAX, was observed, whereas treatment of MCF-7 cells with taxol led to down-regulation of the mRNA levels of all genes examined. Our results support the idea that after long-term clinical studies, mRNA expression analysis of BCL2L12 and other members of the BCL2 gene family may serve as useful molecular markers predicting chemotherapy response in breast cancer.

The Novel Member of the BCL2 Gene Family, BCL2L12, Is Substantially Elevated in Chronic Lymphocytic Leukemia Patients, Supporting Its Value As a Significant Biomarker

BCL2L12 is a recently identified gene belonging to the BCL2 family, members of which are implicated in hematologic malignancies, including chronic lymphocytic leukemia (CLL). The aim of this study was to analyze the mRNA expression of the novel apoptosis-related gene BCL2L12 in patients with CLL and to examine its prognostic and predictive value and potential clinical application as a novel molecular biomarker for CLL. For this purpose, total RNA was isolated from peripheral blood of 65 CLL patients and 23 healthy donors. An ultrasensitive quantitative real-time polymerase chain reaction methodology for BCL2L12 and BCL2 mRNA quantification was developed using SYBR Green chemistry. After preparing cDNA by reverse transcription, relative quantification analysis was performed using the comparative C(T) (2(-ΔΔCT)) method. Furthermore, analysis of IGHV mutational status, CD38 expression, and detection of early apoptosis by double staining with Annexin V-FITC and propidium iodide were performed. According to our findings, BCL2L12 mRNA expression is significantly higher in CLL patients than in healthy donors. Receiver operating characteristic analysis demonstrated that BCL2L12 expression had significant discriminatory value, distinguishing very efficiently CLL patients from the non-leukemic population. Moreover, BCL2L12 expression predicts the presence of CLL, as demonstrated by both univariate and multivariate logistic regression analyses. Finally, high BCL2L12 mRNA levels are associated with advanced clinical stage and predict shorter overall survival in CLL patients.