Hakan Akbulut

Lamivudine prophylaxis for prevention of chemotherapy-induced hepatitis B virus reactivation in hepatitis B virus carriers with malignancies.

Summary.  Although hepatitis B virus (HBV) reactivation in HBV carriers undergoing immunosuppressive therapy is clearly documented, the role of antiviral prophylaxis in such individuals is still controversial. The aim of this study was to determine the efficacy of lamivudine prophylaxis in HBV carriers with haemato/oncological malignancies, who receive chemotherapy. Eighteen HBV carriers with malignancy, who were candidates for chemotherapy, were enrolled. Eight subjects (three with leukaemia, four with lymphoma and one with multiple myeloma) were enrolled for prophylactic lamivudine therapy. The remaining 10 patients (six with leukaemia, three with lymphoma and one with breast cancer) were not treated with lamivudine and were used as a control. Lamivudine was administered beginning on the same day as the chemotherapy and was maintained for a year after chemotherapy was discontinued. No HBV‐related mortality was observed in either group. In the lamivudine‐treated group, none of the subjects had clinical, biochemical or serological evidence of HBV reactivation during the time they were receiving chemotherapy and after their chemotherapy was discontinued. In contrast, five of the 10 HBV carriers not receiving lamivudine therapy experienced a reactivation of HBV infection. This reactivation of HBV was observed during the chemotherapy in four with one individual experiencing a HBV activation 12 months after chemotherapy was discontinued. No lamivudine‐related major adverse effects were observed. Hence prophylactic lamivudine treatment in HBV carriers with haemato/oncological malignancy receiving chemotherapy prevents chemotherapy‐induced HBV reactivation.

An adenoviral vector cancer vaccine that delivers a tumor-associated antigen/CD40-ligand fusion protein to dendritic cells

To develop a method to overcome the anergy that exists in tumor hosts to cancer, we have designed an adenoviral vector for the in vivo activation and tumor antigen loading of dendritic cells. This adenoviral vector encodes a fusion protein composed of an amino-terminal tumor-associated antigen fragment fused to the CD40 ligand (CD40L). Subcutaneous injection of an adenoviral vector encoding a fusion protein of the human papillomavirus E7 foreign antigen linked to the CD40L generates CD8+ T cell-dependent immunoresistance to the growth of the E7-positive syngeneic TC-1 cancer cells in C57BL/6 mice for up to 1 year. We also studied the s.c. injection of a vector carrying the gene for the human MUC-1 (hMUC-1) self-antigen fused to the CD40L. When this vector was injected into hMUC-1.Tg mice, which are transgenic for the hMUC-1 antigen, the growth of syngeneic hMUC-1-positive LL1/LL2hMUC-1 mouse cancer cells was suppressed in 100% of the injected animals. The hMUC-1.Tg mice are anergic to the hMUC-1 antigen before the injection of the vector. These experimental results show that it is possible to use vector injection to activate a long-lasting cellular immune response against self-antigens in anergic animals. The vector-mediated in vivo activation, and tumor-associated antigen loading of dendritic cells does not require additional cytokine boosting to induce the immune response against the tumor cells. This vector strategy may therefore be of use in the development of immunotherapy for the many carcinomas in which the hMUC-1 antigen is overexpressed.

Cytotoxic effect of replication-competent adenoviral vectors carrying L-plastin promoter regulated E1A and cytosine deaminase genes in cancers of the breast, ovary and colon

Prodrug activating transcription unit gene therapy is one of several promising approaches to cancer gene therapy. Combining that approach with conditionally replication-competent viral vectors that are truly tumor specific has been an important objective of recent work. In this study, we report the construction of a new conditionally replication-competent bicistronic adenoviral vector in which the cytosine deaminase (CD) gene and the E1a gene are driven by the L-plastin tumor-specific promoter (AdLpCDIRESE1a). A similar vector driven by the CMV promoter has also been constructed (AdCMVCDIRESE1a) as a control. We have carried out in vitro cytotoxicity in carcinomas of the breast, ovary and colon, and in vivo efficacy studies with these vectors in an animal model of colon cancer. While the addition of the AdLpCDIRESE1a vector to established cancer cell lines showed significant cytotoxicity in tumor cells derived from carcinomas of the breast (MCF-7), colon (HTB-38) and ovary (Ovcar 5), no significant toxicity was seen in explant cultures of normal human mammary epithelial cells (HMEC) exposed to this vector. The addition of 5-fluorocytosine (5FC) significantly increased the cytotoxicity in an additive fashion of both the AdLpCDIRESE1a and AdCMVCDIRESE1a vectors as well as that of the AdLpCD replication incompetent vector to established tumor cell lines. However, no significant cytotoxicity was observed with the addition of 5FC to explant cultures of normal human mammary epithelial cells that had been exposed to the L-plastin-driven vectors. Studies with mixtures of infected and uninfected tumor cell lines showed that the established cancer cell lines infected with the AdLpCDIRESE1a vector generated significant toxicity to surrounding uninfected cells (the “bystander effect”) even at a ratio of 0.25 of infected cells to infected + uninfected cells in the presence of 5FC. The injection of the AdLpCDIRESE1a vector into subcutaneous deposits of human tumor nodules in the nude mice was potentiated by administering 5-FC by intraperitoneal injection. This treatment resulted in a decreased tumor size and a decreased tumor cell growth rate. The mice treated with a combination of the AdLpCDIRESE1a vector intratumoral injection and intraperitoneal 5FC injections lived much longer than the other experimental groups exposed to the viral vector alone or to the combination of the intratumoral AdLpCD replication incompetent vector injections plus intraperitoneal 5-FC injections. These encouraging results with our newly constructed AdLpCDIRESE1a vector suggest a need for further study of its utility in a preclinical model of intracavitary therapy of pleural or peritoneal carcinomatosis.

Differential effects of pharmacological doses of melatonin on malondialdehyde and glutathione levels in young and old rats.

Background: The free radical theory of aging suggests the oxygen-derived species as the causative agents and free radical scavengers as the defense systems in aging process. The exact role of the free radical scavenging effects of melatonin in aging remains to be clarified. Objective: In this experimental study, we investigated the age-related changes of malondialdehyde (MDA), a lipid peroxidation product, and glutathione (GSH) and the effects of exogenous melatonin. Methods: Plasma, liver, and lung MDA and GSH levels of 9- and 28-month-old rats were measured. Results: Plasma, lung, and liver MDA levels of old rats were significantly higher than those of the young ones (p = 0.024, p = 0.005, and p = 0.0007, respectively). However, while the lung GSH levels were found to be significantly decreased in the control group of old rats as compared with young ones (p = 0.005), the liver GSH levels were unchanged. Plasma MDA levels were found to be significantly lower in the melatonin group of old rats as compared with the control group (p = 0.020) but lung and liver MDA levels were not significantly different. There were no significant differences in the levels of measured parameters between both groups of young rats. Conclusion: Our results suggest that increased levels of lipid peroxidation products may have a role in aging, and exogenous melatonin may delay the aging process of tissues by means of its free radical scavenging effects.

A Randomized Phase III Trial of Etoposide, Epirubicin, and Cisplatin Versus 5-Fluorouracil, Epirubicin, and Cisplatin in the Treatment of Patients with Advanced Gastric Carcinoma

Gastric carcinoma is a substantial health problem in Turkey, and the majority of patients present with inoperable disease. The aim of this randomized trial was to assess the activity of 5‐fluorouracil versus etoposide when combined with epirubicin plus cisplatin in patients with advanced gastric carcinoma (AGC).

Exogenous melatonin decreases age-induced lipid peroxidation in the brain.

Aging has been proposed as the major risk factor in most neurodegenerative disorders. Oxidative stress is one of the widely accepted hypotheses to explain the pathogenesis of the senescence-related disorders. In this research report we aimed to study the changes in the levels of malondialdehyde as an indicator of lipid peroxidation and glutathione (GSH) of anti-oxidant status during aging. We also studied the effects of exogenous melatonin (MLT) on lipid peroxidation and glutathione levels of different brain regions. A total of forty-seven, 4 (young), 14 (middle-aged) and 20 (aged) months-old male Wistar-albino rats were used in the study. The MDA levels were significantly correlated with increased age (p<0.001). The MDA levels were similar in the different regions of the brain in the younger rats. However, the MDA levels of the cerebellum were significantly lower than that of the frontal and occipital cortex of the aged animals. Exogenous melatonin treatment significantly decreased the MDA levels of all the examined brain regions in the aged groups (p<0.001). The GSH levels of all the examined brain regions were similar in young and middle-aged rats. The GSH levels were inversely correlated with the increasing age. While exogenous melatonin did not have any significant effect on the GSH levels of the different brain regions in the younger rats, it significantly increased in the aged group. Exogenous melatonin can prevent the increased production of age-related lipid peroxidation products and might have a potential role for retardation of age-related oxidative events.

Vector Targeting Makes 5-Fluorouracil Chemotherapy Less Toxic and More Effective in Animal Models of Epithelial Neoplasms

Purpose: 5-Fluorouracil (5-FU) has been combined in the past with other drugs for the combination chemotherapy for cancers of the breast, ovary, and colon. These drug regimens were limited by the fact that 5-FU fails to kill nondividing cancer cells at the doses that are safe to deliver. The goal of the present study is to test the feasibility of replacing 5-FU in established 5-FU combination chemotherapy with the Ad-LpCDIRESE1A/5-fluorocytosine (5-FC) system for the purpose of reducing toxicity and increasing efficacy. Experimental Design: We have replaced 5-FU in the weekly combination of CPT-11, folinic acid (FA) and 5-FU chemotherapy by 5-FC and an adenoviral vector that carries the L-plastin (Lp) tumor-specific promoter-driven transcription unit encoding the cytosine deaminase gene linked to the E1A gene by an internal ribosomal entry site element. This combination is called “genetic combination therapy.” The goal of using the vector was to decrease the toxicity to normal tissue and to increase the efficacy of therapy in the cancer cells by increasing the concentration of 5-FU sufficiently high that even nondividing cancer cells would be killed by 5-FU through its incorporation into mRNA and consequent inhibition of synthesis of functional proteins. We compared the in vivo efficacy of the genetic combination therapy with the conventional combination chemotherapy in a mouse colon cancer model. Results: Both replication-competent and -noncompetent adenoviral vectors carrying an L-plastin–driven cytosine deaminase transcription unit when combined with 5-FC, CPT-11, and FA showed increased in vitro therapeutic activity that was significantly higher than that of the conventional chemotherapy combination. Tumor-bearing mice treated with the genetic combination therapy showed a statistically significant advantage in terms of increased response rate, response duration, survival, and reduced toxicity when compared with tumor-bearing mice treated with the conventional combination chemotherapy. Conclusions: Replacement of 5-FU in 5-FU–based combination chemotherapy with the Ad-LpCDIRESE1A vector and 5-FU reduces toxicity and increases efficacy. This is a concept that could be potentially applied widely for many forms of cancer treatment.

Cisplatin plus oral etoposide (EoP) combination is more effective than paclitaxel in patients with advanced breast cancer pretreated with anthracyclines: a randomised phase III trial of Turkish Oncology Group

Our objective was to determine whether oral etoposide and cisplatin combination (EoP) is superior to paclitaxel in the treatment of advanced breast cancer (ABC) patients pretreated with anthracyclines. From December 1997 to August 2003, 201 patients were randomised, 100 to EoP and 101 to paclitaxel arms. Four patients in each arm were ineligible. The doses of etoposide and cisplatin were 50 mg p.o. twice a day for 7 days and 70 mg m−2 intravenously (i.v.) on day 1, respectively, and it was 175 mg m−2 on day 1 for paclitaxel. Both treatments were repeated every 3 weeks. A median of four cycles of study treatment was given in both arms. The response rate obtained in the EoP arm was significantly higher (36.3 vs 22.2%; P=0.038). Median response duration was longer for the EoP arm (7 vs 4 months) (P=0.132). Also, time to progression was significantly in favour of the EoP arm (5.5 vs 3.9 months; P=0.003). Median overall survival was again significantly longer in the EoP arm (14 vs 9.5 months; P=0.039). Toxicity profile of both groups was similar. Two patients in each arm were lost due to febrile neutropenia. The observed activity and acceptable toxicity of EoP endorses the employment of this combination in the treatment of ABC following anthracyclines.

THE EFFECTS OF MELATONIN ON HUMORAL IMMUNE RESPONSES OF YOUNG AND AGED RATS

The pineal gland with its effects on immune system and free radicals may have a role on aging process. In this study, we investigated the effects of melatonin (10 mg/kg/d, s.c. for 7 days), the main secretion of the pineal gland, on the humoral immune responses of aged and young male Wistar rats. Eighteen aged (28 months old; 6 in control group and 12 in melatonin group) and 25 young (9 months old; 10 in control group and 15 in melatonin group) rats were given 4×108 sheep erythrocytes i.p. in order to evoke humoral immune responses. After a booster injection at the end of a period of three-weeks following the last melatonin injection, IgM and IgG1 levels were measured. Melatonin was found to increase IgG1 and IgM responses of aged rats when compared to controls (p=0.049 and p=0.007), respectively. In the young rats, while the IgG1 levels of control group were significantly higher than that of the melatonin group (p=0.021), IgM levels were not significantly different (p=0.563). It is concluded that exogenous melatonin may augment the depressed humoral immune responses seen aged rats.

The role of granulocyte‐macrophage‐colony stimulating factor, cortisol, and melatonin in the regulation of the circadian rhythms of peripheral blood cells in healthy volunteers and patients with breast cancer

Abstract: The circulating blood cells show highly reproducible circadian rhythms. However, the factors that regulate these rhythms are not well understood. In the current study, we examined the diurnal variations of peripheral blood cells (white blood cells, neutrophils, lymphocytes), granulocyte‐macrophage‐colony stimulating factor (GM‐CSF), and melatonin levels, and considered the role of melatonin on these rhythms in healthy volunteers and in patients with early breast cancer. Fourteen premenopausal patients with early stage breast cancer (T2, N1 tumors) and 10 premenopausal healthy volunteers were included in the study. Blood samples were taken every 4 hr for a period of 24 hr. Peripheral blood cells were counted by automated analyser and also from peripheral blood films. GM‐CSF levels were measured by ELISA and melatonin levels by radioimmunoassay (RIA). Serum melatonin, cortisol, and GM‐CSF levels, and peripheral blood cell counts showed significant circadian rhythms in healthy volunteers. Except for GM‐CSF, these circadian rhythms were found not to be suppressed in early breast cancer patients. While there were significant correlations of serum GM‐CSF and cortisol levels with peripheral blood cell counts in healthy volunteers, only lymphocyte counts were found to be significantly correlated with serum GM‐CSF and cortisol levels in patients with breast cancer. Serum melatonin levels were found to be significantly correlated with lymphocyte counts in both groups. Our results suggest that peripheral blood cells show significant circadian rhythms in both healthy volunteers and in patients with stage II (T2, N1) breast cancer, and GM‐CSF, cortisol, and melatonin may have a role in the regulation of peripheral blood cell counts.