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Biomedical subjects

D Adhikari

Publications and source records attributed to D Adhikari.

9 recordsLinked to original sources
PubMed2001

Generation of dual resistance to 4-hydroperoxycyclophosphamide and methotrexate by retroviral transfer of the human aldehyde dehydrogenase class 1 gene and a mutated dihydrofolate reductase gene.

The genetic transfer of drug resistance to hematopoietic cells is an attractive approach to overcoming myelosuppression caused by high-dose chemotherapy. Because cyclophosphamide (CTX) and methotrexate (MTX) are commonly used non-cross-resistant drugs, generation of dual drug resistance in hematopoietic cells that allows dose intensification may increase anti-tumor effects and circumvent the emergence of drug-resistant tumors. We constructed a retroviral vector containing both a human cytosolic ALDH-1 cDNA and a human doubly mutated DHFR cDNA (Phe22/Ser31; termed F/S in the description of constructs) to generate increased resistance to both CTX and MTX. Infection of NIH3T3 cells resulted in increased resistance to both 4-hydroperoxycyclophosphamide (4HC) (1.9 +/- 0.1-fold) and MTX (73 +/- 2.8-fold). Transduced human CD34(+) enriched hematopoietic progenitor cells were also resistant to both 4HC and MTX by CFU-GM readout. Lethally irradiated mice transplanted with SFG-ALDH-IRES-F/S or mock-transduced bone marrow cells were treated with high-dose pulse CTX or high-dose CTX/MTX. Animals receiving marrow not transduced with ALDH-1 or mutated DHFR cDNA died from CTX or CTX/MTX toxicity, whereas mice transduced with ALDH-1 and mutated DHFR cDNA-containing marrow were able to tolerate the same doses of CTX or CTX/MTX treatment posttransplant. These data taken together indicate that ALDH-1 overexpression and mutant DHFR increased both 4HC and MTX resistance in vitro and in the in vivo mouse model. This construct may be useful for protecting patients from high-dose CTX- and MTX-induced myelosuppression.

3T3 Cells↗
PubMed2000

Gene therapy for endometrial carcinoma with the herpes simplex thymidine kinase gene.

We investigated whether retrovirus-mediated transfer of the herpes simplex thymidine kinase gene into a human endometrial carcinoma (EC4) cell line can sensitize these cells to the prodrug ganciclovir (GCV) and thereby provide a therapeutic option for this cancer. A retrovirus encoding for the herpes simplex virus tip-1 (HSV) thymidine kinase (tk) gene was generated in which expression of tk is under control of the myeloproliferative sarcoma virus (MPSV) promoter/enhancer. We used human mutated dihydrofolate reductase (DHFR) cDNA as a selectable marker. Expression of tk was confirmed by Northern blot analysis and reverse transcription polymerase chain reaction. We demonstrated that the combination of retrovirally mediated tk gene transfer and GCV treatment effectively inhibits proliferation and causes death of EC4 cells in vitro. A bystander killing effect was observed when 90% of uninfected tumor cells were mixed with only 10% of HSVtk-infected cells. We suggest that a gene therapy approach to endometrial carcinoma can be established using retroviral transfer of HSVtk to tumor cells and subsequent administration of GCV.

Antiviral Agents↗
PubMed2000

Comparison of methotrexate resistance conferred by a mutated dihydrofolate reductase (DHFR) cDNA in two different retroviral vectors.

We previously reported the protection of hematopoietic cells from methotrexate (MTX) toxicity using an N2-based double copy vector containing serine 31 (S31)-mutated dihydrofolate reductase (DHFR) (DC/SV6S31). To examine whether the use of SFG-based dicistronic vectors will lead to improvement in gene transfer over the DC/SV6 vector, we compared the protection provided by MTX to NIH3T3 cells and hematopoietic progenitor cells infected with these retroviral constructs containing the S31 variant DHFR cDNA. In NIH3T3 cells, the 50% effective dose values of MTX conferred by the SFG vector were 8-fold higher than those obtained with the DC/SV6 vector. DHFR mRNA levels were 22-fold and 38-fold higher than that seen for the DC/SV6 vector according to Northern blot and real-time polymerase chain reaction analysis, respectively. However, DHFR protein expression and DHFR enzyme activity were only 1.5-fold and 2-fold higher in the SFG vector, respectively, indicating that the mRNA from the SFG vector is translated less efficiently than the mRNA generated from the DC/SV6 vector. Furthermore, the degree of MTX protection conferred by each vector in both mouse and human hematopoietic cells was the same. These results indicate that the in vitro transduction efficiency and transgene expression of human DHFR in hematopoietic progenitor cells is equally conferred by both vectors.

3T3 Cells↗
PubMed1998

Role of E2F-1 in chemosensitivity.

The E2F family of transcription factors, in partnership with DP proteins, is thought to regulate transcription of genes that encode protein products that are required for DNA synthesis, which include important cancer chemotherapeutic targets such as thymidylate synthase and dihydrofolate reductase. This study was conducted to investigate the effects of overexpression of human E2F-1 cDNA on chemosensitivity in a human fibrosarcoma cell line, HT-1080. The E2F-1-overexpressing HT-1080 cells had a shorter doubling time both in vitro and in vivo. Associated with an up-regulation of TS, E2F-1-transfected cells were more resistant to 5-fluorouracil than were untransfected cells. These E2F-1 transfectants, although resistant to fluoropyrimidines and serum deprivation, were more sensitive to etoposide, doxorubicin, and SN38 (the active metabolite of irinotecan) but not to Taxol.

Antimetabolites, Antineoplastic↗
PubMed1995

Efficacy and safety of oral iron chelating agent deferiprone in beta-thalassemia and hemoglobin E-beta thalassemia.

OBJECTIVES: To assess efficacy and safety of oral iron chelating agent deferiprone (DFP) in patients with beta thalassemia and hemoglobin E-beta thalassemia. DESIGN: Non-randomized study. SETTING: Hematology Out-Patient Department. SUBJECTS: Forty-one patients of beta thalassemia and hemoglobin E-beta thalassemia. INTERVENTIONS: DFP was given to 20 patients, 10 patients of beta thalassemia and 10 with hemoglobin E-beta thalassemia; the rest were taken as controls. RESULTS: A significant fall in serum ferritin was observed in the study group along with rise in urinary iron excretion (p < 0.05). Adverse effects of DFP were nausea and vomiting (30%), significant arthropathy requiring stopping of the drug (30%), and reversible neutropenia in one patient. All these complications could be managed easily with medical supervision and no death or permanent disability was seen. CONCLUSIONS: DFP is an effective and fairly well tolerated oral iron chelating agent. The side effects that occur can be tackled easily if monitored properly.

Administration, Oral↗
PubMed1991

Prevalence of hepatitis B virus (HBV) markers and human immunodeficiency virus (HIV) in employees of a blood transfusion centre.

Blood bank staff, 8 out of 25 (32%) have been exposed to hepatitis B virus (HBV) and the prevalence of HBV markers in blood bank employees handling high risk subjects show hepatitis B surface antigen (n = 1), hepatitis B surface antibody (n = 7), hepatitis B core antibody (n = 6) and combined hepatitis B surface antibody and hepatitis B core antibody (n = 6) seropositivity but all are negative to human immunodeficiency virus (HIV). Serum alanine aminotransferase was raised in the employees than normal subjects and it is suggestive of sub-clinical hepatitis. The employees of blood bank should be trained for proper handling of test materials and must be periodically monitored for HBV and HIV. Immunisation for HBV is mandatory only for the employees of transfusion centre which handles high risk subjects.

Biomarkers↗
PubMedDate not supplied

Pretreatment of endometrial carcinoma cell lines with butyrate results in upregulation of Bax and correlates with potentiation of radiation induced cell kill.

BACKGROUND: Endometrial carcinoma is the most common gynecologic malignancy. Surgery has been the standard therapy for stage I and II endometrial carcinoma and radiation therapy either before or after surgery has been used to improve local control especially for high grade lesions. We have used Sodium Butyrate (BA) in order to examine whether endometrial carcinoma cells can be rendered more sensitive to radiation therapy. METHODS: Endometrial carcinoma cells in culture were pretreated with sodium butyrate and then irradiated. Clonogenic survival assay was used to determine percentage of surviving cells. Changes in Bax and Bcl-2 protein levels were determined by Western blot analyses. Effect of Bcl-2 overexpression on induction of Bax in response to butyrate pretreatment was studied in cells transfected with Bcl-2. RESULTS: A 24 h pretreatment of SKUT2 and Hec-1A cells with BA has an additive effect with radiation. Analysis of pro and anti-apoptotic protein levels revealed that the 24 h pretreatment with BA resulted in increased expression of the proapoptotic protein Bax which correlated with potentiation of radiation induced cell kill. Treatment of cells over expressing Bcl-2 with BA did not show induction of Bax suggesting that higher levels of Bcl-2 can block butyrate induced increase in levels of Bax. CONCLUSIONS: Use of BA at lower than toxic doses to upregulate the proapoptotic potential of cancer cells may be useful in an adjuvant or neoadjuvant setting but its success may depend upon the intrinsic Bcl-2 levels in the tumor.

Adenocarcinoma↗
PubMedDate not supplied

Typhoid fever in Dhulikhel hospital, Nepal.

One hundred and twelve cases of typhoid fever presenting in outpatient and emergency department of Dhulikhel Hospital in Nepal were studied. In this study, it was found that 71% typhoid fever cases were less than 30 years of age group with male to female ratio of 3:1. Fever over 5 days followed by headache and chills were major presenting symptoms. Widal test and blood culture for Salmonella typhi were positive in 59% and 49% cases respectively. Two third of our study population had total leucocyte count of normal range. The fever clearance time was significantly better with ofloxacin compared to ciprofloxacin (p < 0.05) and ceftriaxone compared to chloramphenicol (p < 0.05). The release from treatment was significantly shorter with ceftriaxone compared to ofloxacin, ciprofloxacin and chloramphenicol (p < 0.01). Ceftriaxone was found to be 100% sensitive to salmonella typhi. Amoxicillin was only 52.1% sensitive to Salmonella typhi. Early diagnosis and institution of appropriate antibiotic therapy is of paramount importance in the management of typhoid patients.

Adolescent↗