J. Mahajna - Academia.edu (original) (raw)

Papers by J. Mahajna

Cancer Gene Therapy, 2004

Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subseque... more Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent treatment with the prodrug ganciclovir (GCV) is the most common system utilized to date for ''suicide'' gene therapy of cancer. In the current report, we show that HSV-tk gene transduction enhances tumor growth rate of murine colon cancer cells, that are implanted subcutaneously in syngeneic mice, and enhances cyclooxygenase-2 (COX-2) protein expression and prostaglandin E 2 (PGE 2) release in vitro and in vivo. It is further shown that the observed phenomenon is related to the presence of the HSV-tk sequence insert in the retroviral vector used for HSV-tk gene delivery. Transduction of murine colon cancer cells with control vector, carrying the neomycinresistance gene alone, failed to increase tumor growth rate and COX-2 protein expression or PGE 2 production. On the contrary, it even decreased tumor growth, COX-2 protein expression and PGE 2. The growth rate of HSV-tk-transduced murine tumors was significantly reduced by treatment with the selective COX-2 inhibitor nimesulide. Additionally, we demonstrate herein that both enhanced growth rate of HSV-tk-transduced murine tumors and increased levels of PGE 2 in HSV-tk-transduced cells persist upon the development of GCV resistance. Taken together, these results provide a better understanding of the direct effect of HSV-tk gene transduction on tumor cell biology and target tumor development.

Cancer Gene Therapy, 2006

We have previously reported that transduction of murine colon cancer cells (MC38) with herpes sim... more We have previously reported that transduction of murine colon cancer cells (MC38) with herpes simplex virus thymidine kinase (HSV-tk) gene results in a significant enhancement of tumor growth rate in vivo and overexpression of cyclooxygenase-2 (COX-2). Our current study aimed to investigate the involvement of nuclear factor-kappa B (NF-kB), a pivotal transcriptional regulator of COX-2, in the upregulation of COX-2 expression by HSV-tk. It was found that HSV-tk gene transduction of MC38 cells results in significantly enhanced NF-kB activity, increased phosphorylation and degradation of inhibitor-kappa Ba (IkBa) and enhanced translocation of NF-kB to the nucleus. Treatment of HSV-tk-transduced MC38 cells with sulfasalazine, a potent NF-kB inhibitor, led to dose-dependent inhibition of NF-kB activity, IkB phosphorylation and nuclear translocation of NF-kB, accompanied by significantly decreased COX-2 expression and reduced release of prostaglandin E 2. Transient transfection experiments with COX-2 promoter constructs fused to luciferase reporter gene revealed that mutation in NF-kB-responsive element of COX-2 promoter significantly reduced promoter activity in HSV-tk-transduced MC38 and COS-7 cells, whereas it had no effect on promoter activity in the respective wild-type cells. At last, it was found that HSV-tk gene transduction causes significant enhancement of NF-kB activity and COX-2 expression in two additional tumor cell lines, 9L and T24. These findings suggest that HSV-tk gene transduction results in NF-kB pathway activation, which is essential for COX-2 overexpression by HSV-tk.

Biochemical Pharmacology, 2019

Different types of chemotherapeutics are used for cancer treatment. These drugs act on several si... more Different types of chemotherapeutics are used for cancer treatment. These drugs act on several signal pathways, lead to programmed cell death, and damage cancer cells. Although many specific mechanisms of action have been suggested for chemotherapeutics, there are still gaps in understanding their effects. They may affect different components of the cell, particularly proteins with specific functions, such as enzymes. Recently, targeted and immuno therapies were introduced for treatment of different cancers. However, many cancer patients still depend on traditional and well-known drugs. Doxorubicin and platinum-based drugs are among the most frequently used chemotherapeutics. They are highly cytotoxic for cancer cells, but they also act on healthy cells. Hence, it is crucial to understand the mechanisms involved in order to decrease their side effects. Natural products, many of which are also available over-the-counter, may be considered to decrease various cancer drug-induced side effects. This review focuses on the use of these compounds to overcome side effects of chemotherapeutics, primarily doxorubicin and cisplatin, in the liver, kidney, and neuronal systems.

Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholi... more Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholipase C activation and diacylglycerol production. Human gene sequences from the beta and gamma isoforms were cloned and sequenced, and transcriptional regulation was studied. The major PKC beta transcription initiation site was identified by primer extension and S1 nuclease protection. Additional transcription initiation sites were located within a CpG-rich region proximal to the ATG. The transcription initiation site of the PKC gamma gene was identified by primed cDNA synthesis. In transfection experiments, the PKC gamma promoter was expressed at high level in U937 and HL60 cells but not in COS-1 cells. A sequence motif (AnAGATTCanAGAGnCa), reiterated over at least 1 kb, was located approximately 1.5 kb 5' of the PKC gamma translation initiation codon. This repetitive motif is abundant in run-on RNA in the hematopoietic and epithelial cell lines tested. Analysis of promoter deletion ...

The Bax gene is a member of the Bcl2 family that functions to regulate the programmed cell death ... more The Bax gene is a member of the Bcl2 family that functions to regulate the programmed cell death process. A number of Bax isoforms have been previously identified: alpha, beta, gamma, delta, and omega. Here we report the identification and characterization of an additional Bax variant, termed Baxepsilon. The newly identified Bax variant contains a 97-base insertion generated by alternative splicing which includes a previously unidentified exon between exons 4 and 5. The insertion causes the production of a truncated Bax protein, termed Baxepsilon, which encodes a protein of 164 residues with a calculated molecular weight of 18 kDa. The last 69 amino acids of Baxalpha that encompass the BH2 and the TM domains are missing in Baxepsilon. The Baxepsilon protein, when expressed as a GST fusion protein, associated efficiently with Baxalpha, Baxepsilon, Bcl2, and Bcl-xL. In addition, Baxepsilon was active in inducing apoptosis when tested in a transient transfection assay. Furthermore, the...

European Journal of Cancer, 2016

European Journal of Cancer

Molecular Biology …, 2007

MCF7 breast cancer cell line, carrying a luciferase reporter gene under the control of nuclear fa... more MCF7 breast cancer cell line, carrying a luciferase reporter gene under the control of nuclear factor kappa B (NF-jB)-responsive promoter, was established and used for the screening of fungal organic extracts for their ability to interfere with the NF-jB activation pathway. Twenty-eight crude fungal extracts, out of 242, were found to inhibit NF-jB reporter activity by more than 40%. Furthermore, positive extracts were used to evaluate their antiproliferative activity as well as their ability to influence the phosphorylation and degradation levels of IjBa. Fungal extracts prepared from Marasmius oreades and Cyathus striatus showed significant inhibitory effects on the NF-jB activation pathway. Taken together, our results support the notion of the presence of novel activities that might be utilized as cancer therapeutics.

Acta Histochemica, 2012

Chronic inflammation increases the risk of development of several types of malignancies including... more Chronic inflammation increases the risk of development of several types of malignancies including colon cancer. It also represents a paradigm for the connection between inflammation and cancer in terms of epidemiology and mechanistic studies in preclinical models. A key component of inflammation promoting cancer is the transcription factor NF-κB, which is known to play a critical role in the regulation of the inducible nitric oxide synthase (iNOS) gene. iNOS is an enzyme dominantly expressed during inflammatory reactions. Although synthesis of high amounts of nitric oxide (NO) by iNOS has been demonstrated in pathophysiological processes, such as acute or chronic inflammation and tumorigenesis, the role of iNOS activity in these diseases is still not well understood. Analysis of human biopsies of colitis and colon cancer using immunohistochemistry revealed elevated iNOS protein expression levels, which were strongly paralleled by increased expression of nitrotyrosine suggesting that iNOS has been highly activated in these tissues. These results were corroborated in an in vitro study showing the presence of high iNOS levels in a colon cancer cell line (HT-29) following inflammatory stimuli (TNF-α, peroxynitrite). In addition, the involvement of metastatic processes in the colon biopsies was assessed by means of in situ zymography of MMP activation. MMP 2 (gelatinase A) activation was higher in histopathological sections of colitis and cancer compared to controls. Overall, these data strengthen the findings that in inflammation and colon cancer in humans, iNOS expression and tyrosine nitration may be an indicator of cancer development and progression.

Haematologica, 2012

The inhibitory effects of GNF-2 differed constantly between p185 BCR/ABL and p210 BCR/ABL express... more The inhibitory effects of GNF-2 differed constantly between p185 BCR/ABL and p210 BCR/ABL expressing cells. In all three Philadelphia chromosome-positive acute lymphatic leukemia models, p210 BCR/ABL-transformed cells were more sensitive to GNF-2 than were p185BCR/ABL-positive cells. Similar results were obtained for p185 BCR/ABL and the p210 BCR/ABL harboring resistance mutations. Conclusions Our data provide the first evidence of a differential response of p185 BCR/ABL-and p210 BCR/ABL-transformed cells to allosteric inhibition by GNF-2, which is of importance for the treatment of patients with Philadelphia chromosome-positive acute lymphatic leukemia.

Biochemical and biophysical research communications, Jan 27, 1999

Journal of bacteriology, 1986

Escherichia coli integration host factor (IHF), a DNA-binding protein, positively regulates expre... more Escherichia coli integration host factor (IHF), a DNA-binding protein, positively regulates expression of the lambda cII gene. Purified IHF stimulates cII protein synthesis in vitro, suggesting a direct role for host factor in cII expression. Further evidence for a direct role for IHF was obtained with operon and gene fusions between cII and lacZ or cII and galE. Analysis of these fusions in vivo demonstrated that IHF is essential for the initiation of cII translation. Replacement of the entire cII coding sequence with lacZ yielded a gene fusion which was still IHF dependent. However, a cII-galE fusion carrying a hybrid ribosome binding region expressed galE in IHF mutants. These results indicate that sequences which make cII translation IHF dependent lie between the ribosome binding region and the initiating codon of cII. Failure to translate cII activates a transcription terminator located within cII and results in polar effects on downstream transcription. This polarity is suppre...

Prostate cancer (PCa) is the most common male malignancy in many Western countries. Primary PCa i... more Prostate cancer (PCa) is the most common male malignancy in many Western countries. Primary PCa is hormone dependent and is manageable by hormonal therapy. However, it rapidly develops to hormone-refractory tumors due to the accumulation of mutations in the androgen receptor and/or the acquisition of alternative cellular pathways that support proliferation and inhibit apoptosis of prostate cancer. To date, no effective therapy is available for clinically hormone-insensitive or hormone-refractory stages of prostate cancer.

Journal of Ethnopharmacology, 2000

An ethnobotanical survey was carried out in the West Bank to evaluate the relative efficacy of th... more An ethnobotanical survey was carried out in the West Bank to evaluate the relative efficacy of the plants used to treat skin diseases and prostate cancer. A total number of 102 informants, 30 years and older and either native born or had been living in the West Bank for more than 30 years, were interviewed using a previously prepared questionnaire. Of about 165 plant species mentioned by the informants, 63 (38.1%) were mentioned by three or more informants. On the basis of their primary uses, 21 of these plants were reported to relieve skin disorders, 17 for urinary system disorders, 16 for gastric disorders, nine for cancer and prostate disorders, eight for arthritis, five for respiratory problems, and five for other ailments. Indices on fidelity levels (FLs), relative popularity level (RPL), and rank-order priority (ROP) were calculated. Plants were classified in two groups: 'popular' (RPL = 1) or 'unpopular' (RPLB 1). The following plant species were classified as popular in this study: Teucrium polium, Matricaria aurea, Urtica pilulifera, Paronychia argentea, Petroselinum sati6um, and Sal6ia fruticosa. The remaining 57 species were classified as 'unpopular'. Fifty-nine plants were claimed to be effective against cancer and prostate disorders, which include Arum dioscorides, U. pilulifera, Allium sati6um, Viscum cruciatum, and Allium cepa.

Integrative Cancer Therapies, 2011

Prostate cancer is the most common cancer diagnosed in men. Chemotherapy, androgen ablation, and ... more Prostate cancer is the most common cancer diagnosed in men. Chemotherapy, androgen ablation, and androgen antagonist treatments have proven to have significant effects in the early stages of prostate cancer, whereas advanced prostate cancer is resilient to such treatments. The androgen receptor (AR), a ligand-dependent transcription factor, is the major drug target of prostate cancer therapy. Transition to the androgen-independent stage involves the activation of signaling pathways, AR gene mutations, and other mechanisms. Higher basidiomycetes mushrooms have been used since ancient times in folk medicine to treat a diversity of diseases, including cancer. The present study evaluates the antiandrogenic activity of different Coprinus comatus strains in their ability to interfere with AR function. The authors found that the most active extract was C comatus strain 734 extracted with hexane (CC734-H). This extract was able to (1) inhibit AR-mediated reporter activity, (2) inhibit the proliferation and viability of the LNCaP cell line, and (3) inhibit the colony formation of the LNCaP cell line, in comparison to the DU-145, PC-3, and MDA-Kb2 cells. In addition, CC734-H was able to reduce AR levels and prostate-specific antigen gene expression in the LNCaP-treated cell line. This study illustrates the potential of the C comatus mushroom as a natural antiandrogenic modulator that could serve in the treatment of prostatic diseases.

Gene, 1985

We have constructed synthetic operons in which two genes (cat and lacZ or cat and galK) were plac... more We have constructed synthetic operons in which two genes (cat and lacZ or cat and galK) were placed in tandem under the control of the bacteriophage lambda oLpL operator and promoter. Restriction sites were introduced between the promoter and the proximal cat gene or between the cat and lacZ or galK genes. In the latter case, introduction of a transcriptional terminator between the two structural genes should affect only the distal gene. Thus, following induction, the expression of the cat gene serves as an internal control, compensating for changes due to plasmid copy number or possible decrease in transcription initiation. We used these plasmids to select a lambda DNA fragment which includes the N-unresponsive tJ transcriptional terminator. This DNA fragment was inserted between the cat and galK genes. Enzymatic assays of these two gene activities following induction indicate that transcripts initiated at the pL promoter under N+ conditions terminate at tJ between the two genes. S1-nuclease analysis showed that these transcripts terminate at several sites in the tJ region. Similar results were obtained whether the host cells were RNaseIII+ or RNaseIII-. As a control, we showed a complete antitermination of the lambda t'I terminator under similar conditions, indicating that a sufficient amount of the N gene product is made from one N gene copy to suppress terminators carried on multicopy plasmids.

DNA and Cell Biology, 1997

Retinoid X receptors (RXRs) are members of the steroid and thyroid hormone receptor superfamily o... more Retinoid X receptors (RXRs) are members of the steroid and thyroid hormone receptor superfamily of hormone-dependent transcription factors that mediate the pleiotropic effect of retinoids. Here, we report the initial characterization of an isoform of hRXR beta, termed hRXR beta3, which was previously identified as an H-2RIIBP isoform (Epplen and Epplen, 1992). The hRXR beta3 isoform cotains an in-frame insertion of four amino acids (SLSR) in the ligand binding domain at codon 419. The isoform is generated by alternate use of a 3' splice acceptor site and was detectable by reverse transcription polymerase chain reaction (RT-PCR) in all human tumor cell lines and mouse tissues examined. Chimeric receptors, in which the ligand-binding domain of hRXR alpha was substituted by the corresponding domain from hRXR beta3, were used to investigate the consequences of the SLSR insertion on the transactivation and DNA-binding functions of the chimeric receptor. Co-transfection assays revealed that a chimera RXR alpha/beta3 receptor failed to transactivate the RXR-specific CRBPII promoter, whereas the identical chimera lacking the SLSR insertion was active. The RXR alpha/beta3 receptor exhibited dominant negative activity against active retinoid X and retinoic acid receptors on retinoid-responsive promoters. Moreover, the RXR alpha/beta3 protein failed to interact physically with the retinoic acid receptor (RAR) to form heterodimers as detected by physical association assays, and failed to bind DNA containing an RAR-responsive element. Therefore, this suggests that the SLSR insertion in the ligand-binding domain of the RXR alpha/beta3 receptor is responsible for the altered behavior of the chimera. Our findings raise the possibility that RXR alpha/beta3, and perhaps hRXR beta3 isoform, function by titrating a limiting adaptor molecule that is involved in mediating retinoid function.

DNA and Cell Biology, 1995

Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholi... more Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholipase C activation and diacylglycerol production. Human gene sequences from the beta and gamma isoforms were cloned and sequenced, and transcriptional regulation was studied. The major PKC beta transcription initiation site was identified by primer extension and S1 nuclease protection. Additional transcription initiation sites were located within a CpG-rich region proximal to the ATG. The transcription initiation site of the PKC gamma gene was identified by primed cDNA synthesis. In transfection experiments, the PKC gamma promoter was expressed at high level in U937 and HL60 cells but not in COS-1 cells. A sequence motif (AnAGATTCanAGAGnCa), reiterated over at least 1 kb, was located approximately 1.5 kb 5&amp;#39; of the PKC gamma translation initiation codon. This repetitive motif is abundant in run-on RNA in the hematopoietic and epithelial cell lines tested. Analysis of promoter deletion constructs by transient transcription assays in U937, IM9, and COS-1 cells showed negative regulation of the PKC beta promoter by sequences located between -3,000 and -690. although no homology between PKC beta and PKC-gamma 5&amp;#39;-flanking sequences was observed, both PKC beta and PKC gamma promoters were potently induced by 12-phorbol 13-myristate in transfected U937 cells.

Cancer Gene Therapy, 2004

Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subseque... more Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent treatment with the prodrug ganciclovir (GCV) is the most common system utilized to date for ''suicide'' gene therapy of cancer. In the current report, we show that HSV-tk gene transduction enhances tumor growth rate of murine colon cancer cells, that are implanted subcutaneously in syngeneic mice, and enhances cyclooxygenase-2 (COX-2) protein expression and prostaglandin E 2 (PGE 2 ) release in vitro and in vivo. It is further shown that the observed phenomenon is related to the presence of the HSV-tk sequence insert in the retroviral vector used for HSV-tk gene delivery. Transduction of murine colon cancer cells with control vector, carrying the neomycinresistance gene alone, failed to increase tumor growth rate and COX-2 protein expression or PGE 2 production. On the contrary, it even decreased tumor growth, COX-2 protein expression and PGE 2. The growth rate of HSV-tk-transduced murine tumors was significantly reduced by treatment with the selective COX-2 inhibitor nimesulide. Additionally, we demonstrate herein that both enhanced growth rate of HSV-tk-transduced murine tumors and increased levels of PGE 2 in HSV-tk-transduced cells persist upon the development of GCV resistance. Taken together, these results provide a better understanding of the direct effect of HSV-tk gene transduction on tumor cell biology and target tumor development.

Cancer Gene Therapy, 2004

Cancer Gene Therapy, 2006

Biochemical Pharmacology, 2019

European Journal of Cancer, 2016

European Journal of Cancer

Molecular Biology …, 2007

Acta Histochemica, 2012

Haematologica, 2012

Biochemical and biophysical research communications, Jan 27, 1999

Journal of bacteriology, 1986

Journal of Ethnopharmacology, 2000

Integrative Cancer Therapies, 2011

Gene, 1985

DNA and Cell Biology, 1997

DNA and Cell Biology, 1995

Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholi... more Protein kinase C (PKC) serine/threonine kinases transduce cellular signals initiated by phospholipase C activation and diacylglycerol production. Human gene sequences from the beta and gamma isoforms were cloned and sequenced, and transcriptional regulation was studied. The major PKC beta transcription initiation site was identified by primer extension and S1 nuclease protection. Additional transcription initiation sites were located within a CpG-rich region proximal to the ATG. The transcription initiation site of the PKC gamma gene was identified by primed cDNA synthesis. In transfection experiments, the PKC gamma promoter was expressed at high level in U937 and HL60 cells but not in COS-1 cells. A sequence motif (AnAGATTCanAGAGnCa), reiterated over at least 1 kb, was located approximately 1.5 kb 5&amp;#39; of the PKC gamma translation initiation codon. This repetitive motif is abundant in run-on RNA in the hematopoietic and epithelial cell lines tested. Analysis of promoter deletion constructs by transient transcription assays in U937, IM9, and COS-1 cells showed negative regulation of the PKC beta promoter by sequences located between -3,000 and -690. although no homology between PKC beta and PKC-gamma 5&amp;#39;-flanking sequences was observed, both PKC beta and PKC gamma promoters were potently induced by 12-phorbol 13-myristate in transfected U937 cells.

Cancer Gene Therapy, 2004

Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subseque... more Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent treatment with the prodrug ganciclovir (GCV) is the most common system utilized to date for ''suicide'' gene therapy of cancer. In the current report, we show that HSV-tk gene transduction enhances tumor growth rate of murine colon cancer cells, that are implanted subcutaneously in syngeneic mice, and enhances cyclooxygenase-2 (COX-2) protein expression and prostaglandin E 2 (PGE 2 ) release in vitro and in vivo. It is further shown that the observed phenomenon is related to the presence of the HSV-tk sequence insert in the retroviral vector used for HSV-tk gene delivery. Transduction of murine colon cancer cells with control vector, carrying the neomycinresistance gene alone, failed to increase tumor growth rate and COX-2 protein expression or PGE 2 production. On the contrary, it even decreased tumor growth, COX-2 protein expression and PGE 2. The growth rate of HSV-tk-transduced murine tumors was significantly reduced by treatment with the selective COX-2 inhibitor nimesulide. Additionally, we demonstrate herein that both enhanced growth rate of HSV-tk-transduced murine tumors and increased levels of PGE 2 in HSV-tk-transduced cells persist upon the development of GCV resistance. Taken together, these results provide a better understanding of the direct effect of HSV-tk gene transduction on tumor cell biology and target tumor development.