(1/304) Potentiation of anti-cancer drug activity at low intratumoral pH induced by the mitochondrial inhibitor m-iodobenzylguanidine (MIBG) and its analogue benzylguanidine (BG).
Tumour-selective acidification is of potential interest for enhanced therapeutic gain of pH sensitive drugs. In this study, we investigated the feasibility of a tumour-selective reduction of the extracellular and intracellular pH and their effect on the tumour response of selected anti-cancer drugs. In an in vitro L1210 leukaemic cell model, we confirmed enhanced cytotoxicity of chlorambucil at low extracellular pH conditions. In contrast, the alkylating drugs melphalan and cisplatin, and bioreductive agents mitomycin C and its derivative EO9, required low intracellular pH conditions for enhanced activation. Furthermore, a strong and pH-independent synergism was observed between the pH-equilibrating drug nigericin and melphalan, of which the mechanism is unclear. In radiation-induced fibrosarcoma (RIF-1) tumour-bearing mice, the extracellular pH was reduced by the mitochondrial inhibitor m-iodobenzylguanidine (MIBG) or its analogue benzylguanidine (BG) plus glucose. To simultaneously reduce the intracellular pH, MIBG plus glucose were combined with the ionophore nigericin or the Na+/H+ exchanger inhibitor amiloride and the Na+-dependent HCO3-/Cl- exchanger inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS). Biochemical studies confirmed an effective reduction of the extracellular pH to approximately 6.2, and anti-tumour responses to the interventions indicated a simultaneous reduction of the intracellular pH below 6.6 for at least 3 h. Combined reduction of extra- and intracellular tumour pH with melphalan increased the tumour regrowth time to 200% of the pretreatment volume from 5.7 +/- 0.6 days for melphalan alone to 8.1 +/- 0.7 days with pH manipulation (P < 0.05). Mitomycin C related tumour growth delay was enhanced by the combined interventions from 3.8 +/- 0.5 to 5.2 +/- 0.5 days (P < 0.05), but only in tumours of relatively large sizes. The interventions were non-toxic alone or in combination with the anti-cancer drugs and did not affect melphalan biodistribution. In conclusion, we have developed non-toxic interventions for sustained and selective reduction of extra- and intracellular tumour pH which potentiated the tumour responses to selected anti-cancer drugs. (+info)
(2/304) Biosynthesis of DNA, RNA and proteins by mouse embryos cultured in the presence of a teratogenic dose of chlorambucil.
The effect of chlorambucil on the rates of DNA, RNA, and protein synthesis in mouse embryos was investigated using a system of whole embryo culture. Embryos were isolated on the 11th day of gestation (33 +/- 3 somites) and grown in culture media for periods of 4-8 h. Reichert's membrane and most of the placental tissue was removed leaving only the amnion and visceral yolk-sac surrounding the embryo. In the presence of teratogenic doses of chlorabucil (15 mug/ml) the rate of DNA synthesis was significantly decreased at 4 and 8 h. RNA and protein synthesis were not inhibited at either of these times. A trend toward decreasing rates of protein synthesis at some time beyond 8 h was noted, but not tested. (+info)
(3/304) Chemotherapeutic options in chronic lymphocytic leukemia: a meta-analysis of the randomized trials. CLL Trialists' Collaborative Group.
BACKGROUND: The randomized trials that evaluate the timing and intensity of initial chemotherapy for chronic lymphocytic leukemia (CLL) have, in general, been too small to provide separately reliable results. We compared the effects on survival of the following: a) immediate versus deferred chemotherapy for early-stage CLL and b) combination chemotherapy (e.g., cyclophosphamide and vincristine plus prednisone/prednisolone [COP] or COP plus doxorubicin [CHOP]) versus single-agent chlorambucil as first-line treatment for more advanced disease. METHODS: All relevant randomized trials, whether published or not, were sought for a collaborative meta-analysis involving centralized review of the data for each patient. RESULTS: There were 2048 patients with early disease in six trials of immediate versus deferred chemotherapy (chlorambucil or chlorambucil plus prednisone/prednisolone). The 10-year survival was slightly worse (but not statistically significantly so) with immediate chemotherapy (44% versus 47% survival; difference = -3%; 95% confidence interval [CI] = -10% to 4%). There were another 2022 patients in 10 trials of combination chemotherapy versus chlorambucil, with or without prednisone/prednisolone. The 5-year survival was 48 % in both cases (difference = 0%; 95% CI = -6% to 5%). A subgroup of six of these 10 trials involved an anthracycline-containing regimen but again overall survival appeared no better than with chlorambucil (anthracycline-based regimen: 325 deaths among 627 patients; chlorambucil: 306 deaths among 636 patients; death rate ratio = 1.07; 95% CI = 0.91-1.25; not statistically significant). CONCLUSIONS: In terms of survival, these trials support a conservative treatment strategy for CLL, i.e., no chemotherapy for most patients with early-stage disease, and single-agent chlorambucil as the first line of treatment for most patients with advanced disease, with no evidence of benefit from early inclusion of an anthracycline. This strategy will, however, need to be reconsidered as mature results become available from trials of other agents. (+info)
(4/304) Effect of Epstein-Barr virus infection on response to chemotherapy and survival in Hodgkin's disease.
We have analyzed paraffin sections from 190 patients with histologically confirmed Hodgkin's disease (HD) for the presence of Epstein-Barr virus (EBV) using in situ hybridization to detect the EBV-encoded Epstein-Barr virus early RNAs (EBERs) and immunohistochemistry to identify latent membrane protein-1 (LMP1) expression. EBV was present in the tumor cells in 51 HD cases (27%) and was mainly confined to the mixed cellularity and nodular sclerosis subtypes. There was no difference between EBV-positive and EBV-negative HD patients with regard to age, clinical stage, presentation, and the number of alternating chemotherapy cycles of ChIVPP and PABIOE received. The complete remission rate after study chemotherapy was 80% in EBV-positive patients versus 69% in EBV-negative patients (P =.05). The 2-year failure-free survival rate was significantly better for EBV-positive patients when compared with the EBV-negative HD group (P =.02). Although 2-year and 5-year overall survival rates were better for EBV-positive HD patients, the differences were not statistically significant (P =.18 and P =.40, respectively). In conclusion, the results confirm the favorable prognostic value of EBV in the tumor cells of HD patients and suggest important differences in response to chemotherapy between EBV-positive and EBV-negative patients. (+info)
(5/304) Chlorambucil induction of HsRad51 in B-cell chronic lymphocytic leukemia.
Our previous studies with B-cell chronic lymphocytic leukemia (B-CLL) have suggested that one of the mechanisms of nitrogen mustard (NM) drug resistance is increased repair of drug-induced damage. We have postulated that recombination may play a crucial role in this process. The human homologue of Rad51, (HsRad51), has homology to the RecA protein in Escherichia coli, which is implicated in recombination repair and induction of DNA repair enzymes. In this report, we have examined the expression and distribution of HsRad51 protein in lymphocytes from patients with B-CLL to see whether the expression of HsRad51 is associated with NM damage to the malignant B lymphocytes, specifically chlorambucil (CLB), which is the standard alkylating agent used to treat patients with B-CLL. We have analyzed the intracellular distribution of HsRad51 protein in these lymphocytes before and after treatment with CLB by immunofluorescence. In vitro CLB treatment induces Rad51 expression, as measured by increased immunopositive staining in all CLL samples. In the CLB-resistant CLL lymphocytes, there was a linear correlation between induction of Rad51 protein at 5.4 microM CLB and the in vitro LD50 dose of CLB. Surprisingly, although it has been reported that Rad51 is induced in S phase and only 10% of cells from cell lines expressed positive immunostaining for Rad51, our CLL lymphocytes, which were not subjected to in vitro drug exposure, were 90% positive for Rad51, despite their nonproliferative state, which suggests that there is chronic activation of the protein. Our results suggest that CLB activates HsRad51-directed recombination repair and that this process may be important in NM drug-induced cytotoxicity. (+info)
(6/304) High-dose BEAM chemotherapy with autologous haemopoietic stem cell transplantation for Hodgkin's disease is unlikely to be associated with a major increased risk of secondary MDS/AML.
Hodgkin's disease is curable in the majority of patients, although a proportion of patients are resistant to or relapse after initial therapy. High-dose therapy with autologous stem cell support has become the standard salvage therapy for patients failing chemotherapy, but there have been reports of a high incidence of myelodysplasia/acute myeloid leukaemia (MDS/AML) following such treatment. Patients who receive such therapy form a selected group, however, who have already been subjected to other leukaemogenic factors, such as treatment with alkylating agents. In order to ascertain the true risk of MDS/AML, comparison must be made with other patients subjected to the same risks but not undergoing transplantation. We report a retrospective comparative study of 4576 patients with Hodgkin's disease from the BNLI and UCLH Hodgkin's databases, which includes 595 patients who have received a transplant. Statistical analysis including Cox's proportional hazards multivariate regression model with time-dependent covariates was employed. This analysis reveals that the risk of developing MDS/AML was dominated by three factors, namely quantity of prior therapy (relative risk [RR] 2.01, 95% confidence intervals [CI] 1.49-2.71, for each treatment block, P < 0.0001) and whether the patient had been exposed to MOPP (RR 3.61, 95% CI 1.64-7.95, P = 0.0009) or lomustine chemotherapy (RR 4.53, 95% CI 1.96-10.44, P = 0.001). Following adjustment for these factors in the multivariate model the relative risk associated with transplantation was 1.83 (95% CI 0.66-5.11, P = 0.25). This study provides no evidence of a significantly increased risk of MDS/AML associated with BEAM therapy and autologous transplantation in Hodgkin's disease. Concern over MDS/AML should not mitigate against the timely use of this treatment modality. (+info)
(7/304) The role of drug transport in resistance to nitrogen mustard and other alkylating agents in L518Y lymphoblsts.
An investigation was undertaken of the mechanism of resistance to nitrogen mustard (HN2) and other alkylating agents, with particular emphasis on the interaction between cross-resistance and drug transport mechanisms in L5178Y lymphoblasts. Dose-survival curves demonstrated that the D0 for HN2-sensitive cells (L5178Y) treated with HN2 in vitro was 9.79 ng/ml and the D0 for HN2-resistant cells (L5178Y/HN2) was 181.11 ng/ml; thus, sensitive cells were 18.5-fold more responsive than were resistant cells and the difference was highly significant (p less than 0.001). A similar evaluation of 5 additional alkylating agents, including chlorambucil, melphalan, 1,3-bis(2-chloroethyl)-l-nitrosourea, Mitomycin C, and 2,3,5-tris(ethyleneimino)-1,4-benzoquinone, revealed that L5178Y/HN2 cells were also cross-resistant, in part, to each of these compounds. Furthermore, the degree of cross-resistance was remarkably similar; for each drug, dose-survival studies showed that HN2-resistant cells were approximately 2- to 3-fold more resistant to therapy than were sensitive cells. L5178Y/HN2 cells were also cross-resistant to cyclophosphamide in vivo; after treatment with cyclophosphamide, DBA/2 female mice that were given inoculations of L5178Y cells, but not those given transplants of L5178Y/HN2 cells, showed a significant prolongation of survival time (p less than 0.01). Transport of HN2, hydrolyzed derivative of HN2 and choline by L5178Y lymphoblasts in vitro was not competitively inhibited by any of the other alkylating agents, suggesting that transport of these compounds was by an independent mechanism. These findings suggest that the mechanism whereby L5178Y/HN2 cells are cross-resistant to other alkylating agents may involve nontransport factors and that these other drugs may bypass a major portion of HN2 resistance by using independent transport systems. (+info)
(8/304) Clinical features and treatment outcome of idiopathic membranous nephropathy in Chinese patients.
We retrospectively studied the clinical course and treatment outcome of idiopathic membranous nephropathy (IMN) amongst 38 Chinese patients (25 male, 13 female, age 51.6 +/- 14.6 years, follow-up duration 58.2 +/- 51.1 months) who presented over a 10-year review period. Eight never received any form of specific treatment (group I), seven received oral corticosteroid alone for 6-9 months (group II), 17 were given corticosteroid plus cyclophosphamide for 6-12 months (group III), and six were treated with methylprednisolone alternating with chlorambucil every other month for 6 months (group IV). No untoward effect from drugs sufficient to alter the dosage used was recorded. After 6 months of treatment, over 50% of patients went into remission: a significant reduction in proteinuria (p = 0.01, 0.01, 0.02) with a corresponding rise in serum albumin levels (p = 0.01, 0.01, 0.04) was observed in groups II, III, and IV, respectively, but not in group I. During follow-up, one patient in each of groups I, III, IV, and two of group II developed renal function deterioration, which correlated with an abnormal presenting serum creatinine. In six group I and eight group III patients who have been followed for at least 5 years, there was progressive reduction in proteinuria in group III (p < 0.05), but not in group I: serum creatinine has remained unchanged in both groups. IMN runs a benign course in Chinese patients in Hong Kong, with 2.6% of patients going into end-stage renal failure during the study period. Contrary to reports in Caucasians, there is similar treatment response to steroid alone or a combination of steroid and cytotoxic agents. (+info)