Preoperative evaluation of the chemosensitivity of breast cancer by means of double phase 99mTc-MIBI scintimammography

The chemosensitivity of breast cancer is important for its management, but it is difficult to evaluate preoperatively. Tc-99m hexakis-2-methoxyisobutylisonitrile (MIBI) scintimammography has been reported to indicate the expression of P-glycoprotein, which is one factor concerned with multidrug resistance. We developed a chemosensitivity assay by using surgical specimens to investigate whether 99mTc-MIBI scintimammography findings before the operation are related to chemosensitivity according to our assay. Fifteen patients with primary breast cancer were enrolled into the study. Early and delayed images were obtained at 10 and 120 minutes after intravenous injection of 99mTc-MIBI, respectively. Regions of interest were placed on the tumors and the contralateral healthy breasts in each patient to estimate 99mTc-MIBI uptake in the tumor, and retention indices were then calculated to assess the washout of 99mTc-MIBI. Chemosensitivity assay was performed by incubating surgical specimens with anticancer agents such as doxorubicin, epirubicin, pinorubicin, mitomycin C, cisplatin and 5-fluorouracil. 99mTc-MIBI washout on scintimammography was successfully related to inhibition ratios on chemosensitivity tests when compared with 99mTc-MIBI uptake by the tumor. In particular, high correlation coefficients were obtained between the retention index of 99mTc-MIBI and the inhibition ratios of doxorubicin (r = 0.75), epirubicin (r = 0.60) and pinorubicin (r = 0.62), but poor correlation was found for mitomycin C (r = 0.44) and cisplatin (r = 0.31). Our results indicate that the retention index of 99mTc-MIBI is closely correlated to chemosensitivity to anthracyclines, suggesting that double-phase scintimammography allows preoperative prediction of chemosensitivity of breast cancer.     

Tumor heterogeneity and in vitro chemosensitivity testing in ovarian cancer

OBJECTIVE: Our purpose was to study the heterogeneity of drug response in fresh human ovarian tumors to chemotherapeutic agents in an in vitro chemosensitivity assay. STUDY DESIGN: This assay evaluates total tumor cell kill by measuring the intracellular adenosine triphosphate levels of untreated controls and drug-exposed cells at various doses after culture for 6 days. The surviving fraction is calculated by dividing the treated values with the control values. One hundred tumors were tested against four single drugs (cisplatin, the active metabolite of cytoxan, 4-hydroxyperoxy-cyclophosphamide, Taxol, and carboplatin) and two drug combinations (cisplatin plus 4-hydroxyperoxy-cyclophosphamide; cisplatin plus Taxol). RESULTS: There is great variation in the degree of cell death for single drugs and drug combinations among the 100 tumors tested. CONCLUSION: More effective clinical response to chemotherapy may be achieved in patients with ovarian cancer by selecting the most active drugs for chemotherapy, on the basis of in vitro chemosensitivity test results for individual patients.     

Remission of human breast cancer xenografts on therapy with humanized monoclonal antibody to HER-2 receptor and DNA-reactive drugs

HER-2 oncogene encodes a transmembrane growth factor receptor that is overexpressed in 25-30% of patients with primary breast and ovarian cancer. A murine monoclonal antibody, 4D5, to the extracellular domain of HER-2 receptor elicits cytostatic growth inhibition of tumor cells overexpressing HER-2 protein, but clinical use of this antibody is limited by genesis of human anti-mouse antibodies. To avoid this problem, a recombinant humanized 4D5 monoclonal antibody (rhuMAb HER-2) was developed and tested using a human tumor xenograft model. Human breast and ovarian cancer cells which overexpress HER-2 were inhibited in vivo by the rhuMAb HER-2 antibody. Tumor growth relative to control was reduced at all doses of antibody tested, and the magnitude of growth inhibition was directly related to dose of rhuMAb HER-2. Tumor growth resumed on termination of antibody therapy, indicating a cytostatic effect. To elicit a cytotoxic response, human breast tumor xenografts were treated with a combination of antibody and antitumor drugs, cisplatin or doxorubicin. The combination of antibody with either cisplatin or doxorubicin resulted in significantly greater growth inhibition, with the cisplatin combination demonstrating a greater response. In addition, therapy with cisplatin and antireceptor antibody elicited complete tumor remissions after 2-3 cycles of therapy. The schedule of administration of anti-receptor antibody and cisplatin was critical for occurrence of antibody-induced potentiation in cisplatin cytotoxicity. Enhanced killing of tumor cells was found only if antibody and drug were given in close temporal proximity. Since interference with DNA repair pathways may contribute to this receptor-enhanced chemosensitivity, repair of cisplatin-damaged reporter DNA (pCMV-beta) was determined in human breast cells. As in studies of antibody-enhanced cisplatin cytotoxicity in vivo, treatment with rhuMAb HER-2 blocked the repair of cisplatin-damaged DNA only if the antibody was administered in close temporal proximity to transfection of the drug-exposed reporter DNA. An alternative measure of DNA repair, unscheduled DNA synthesis, was also assessed. Treatment with either cisplatin or doxorubicin led to an increase in unscheduled DNA synthesis that was reduced by combined therapy with antireceptor antibody specific to HER-2-overexpressing breast cancer cells. Using a direct measure of DNA repair, therapy of HER-2-overexpressing cells with rhuMAb HER-2 also blocked the removal of cisplatin-induced DNA adducts. Expression of p21/WAF1, an important mediator of DNA repair, was disrupted in breast cancer cells with HER-2 overexpression, but not in control cells, after treatment with HER-2 antibody, thus suggesting cross-communication between the HER-2 signaling and DNA repair pathways. These data demonstrate an in vivo antiproliferative effect of rhuMAb HER-2 on tumors that overexpress HER-2 receptor and a therapeutic advantage in the administration of the antireceptor antibody in combination with chemotherapeutic agents.     

Percutaneous intratumoral injection of cisplatin microspheres in tumor-bearing rats to diminish acute nephrotoxicity

Poly(D,L-lactide) microspheres loaded with cisplatin (PLA-CDDP MS) were prepared by a solvent evaporation technique for direct intratumoral injection. The microspheres, 50-100 microns, containing 40.04% of cisplatin produce sustained release in vitro. PLA-CDDP MS (6 mg/kg body weight of cisplatin) suspensions were injected intratumorally into mammary tumors in rats. Cisplatin solution (6 mg/kg body weight) was injected either intratumorally or intraperitoneally in two groups. After treatments, the tumor size decreased in each of the groups as a function of time. Sixteen days post-injection, the tumors had either disappeared or significantly shrunk. PLA-CDDP MS had a similar antitumor effect compared with cisplatin aqueous solution. Blood urea nitrogen, serum creatinine and histopathology examinations revealed that the renal toxicity in the PLA-CDDP MS group was significantly less than in the control groups. These results indicate that intratumoral injection of PLA-CDDP MS maintains anticancer potency and reduces acute renal toxicity.     

Bax is an important determinant of chemosensitivity in pediatric tumor cell lines independent of Bcl-2 expression and p53 status

Susceptibility of a tumor cell to undergo chemotherapy-induced apoptosis appears to be dependent upon the balance of proapoptotic and survival factors that are expressed within any given cell. We have chosen to evaluate how expression of several of these proteins influences chemosensitivity of a panel of 10 pediatric tumor cell lines chosen from three tumor histiotypes: neuroblastoma, rhabdomyosarcoma, and pediatric glial tumors. The proteins evaluated were p53 and six members of the Bax/Bcl-2 family: three proapoptotic proteins (Bax, Bak, and Bcl-xS) and three survival factors (Bcl-2, Bcl-xL, and Mcl-1). We investigated whether there was any relationship between endogenous expression of these proteins and chemosensitivity (or resistance) to three chemotherapeutic agents that directly damage DNA (doxorubicin, actinomycin D, and topotecan) and a mitotic spindle poison (vincristine). Even though exogenous overexpression of wild-type p53 has been associated with a chemosensitive phenotype in several model systems we demonstrated no such relationship in these studies. In addition, expression levels of Bcl-2, Bcl-xL, Bcl-xS, Bak, or Mcl-1 did not correlate with sensitivity or resistance to the four drugs. However, there was a statistically significant correlation between endogenous levels of Bax protein and sensitivity to both doxorubicin and actinomycin D. We conclude that even though many proteins such as p53 and Bcl-2 have been shown to influence drug response when exogenously overexpressed in model systems, in unmodified cell lines endogenous protein levels may not generate the same results. We have demonstrated that endogenous Bax expression was the only protein found to be associated with chemosensitivity across the three different tumor histiotypes and propose that analysis of Bax may be a more useful prognostic indicator for tumor response to therapy than either p53 or Bcl-2.     

Bcl-2 and Bcl-XL can differentially block chemotherapy-induced cell death

Bcl-2 and its homologue Bcl-XL are expressed in a variety of tumors and their expression modulates the sensitivity of tumor cells to a wide spectrum of chemotherapeutic agents and gamma-irradiation. In the present report, we generated clones of FL5.12 lymphoid cells with similar levels of Bcl-2 and Bcl-XL using the Flag epitope to determine if these survival proteins could provide equivalent protection when challenged with chemotherapy or gamma-irradiation. Using four M-phase specific chemotherapeutic agents, Bcl-XL and Bcl-2 provided similar protection against vincristine and vinblastine whereas Bcl-XL afforded as much as 50% greater cell viability than Bcl-2 against etoposide and teniposide-induced cell death. In addition, Bcl-XL provided significantly greater cell viability than Bcl-2 against methotrexate, fluorouracil, and hydroxyurea, three S-phase specific agents. In apoptosis induced by gamma-irradiation and cisplatin, two antitumor treatments that are cell-cycle phase-nonspecific agents, both Bcl-XL and Bcl-2 conferred similar protection against gamma-irradiation, but Bcl-XL provided better protection than Bcl-2 against cisplatin. These results indicate that Bcl-XL and Bcl-2 confer a differential ability to protect against chemotherapy-induced cell death, which appears to be dependent on the molecular mechanism targeted by the drug rather than its cell-cycle phase specificity.     

The potentiation of the effect of radiation treatment by intratumoral delivery of cisplatin

PURPOSE: To compare potentiation of the effects of acute or fractionated radiation by cisplatin when the drug was delivered intratumorally by implanted biodegradable polymer, by intraperitoneal injection, or by intraperitoneal osmotic pump. METHODS AND MATERIALS: Radiation was delivered to a mouse tumor (RIF-1) either in a single dose or in a fractionated regime in conjunction with cisplatin delivered either as a bolus injection, with an osmotic pump, or with a biodegradable polymer rod containing cisplatin. The osmotic pump was implanted in the intraperitoneal cavity of the mouse while the polymer implants were placed directly in the tumor. As the polymer degrades, the drug is released at the treatment site leading to high local concentrations. The osmotic pump, in contrast, leads to prolonged systemic exposure to the drug at low concentrations. Tumor growth delay (TGD) was used as an endpoint in these experiments. RESULTS: The most effective treatment protocol, in terms of potentiating the effects of radiation was cisplatin delivered by polymer implanted 2 days before an acute dose of radiation (growth modification factor [DMF] = 2.2). Comparison of single and multifraction regimes where polymer implant was on the same day as the commencement of treatment showed greater potentiation of the effect of fractionated than of acute radiation treatment with the DMF for fractionated treatment remaining relatively constant (1.5-1.9) for 5, 8, and 12 fraction treatments. Cisplatin delivered via the osmotic pump did not deliver a high enough dose of cisplatin to produce therapeutic effect in this mouse tumor model and had little impact on response to treatment. CONCLUSIONS: Our results indicated that cisplatin delivered intratumorally by biodegradable polymer implant was effective in potentiating the effect of both acute and fractionated radiation. For the fractionated treatments the effect was maintained with increasing fraction numbers and treatment time.     

Population dynamics of the deer mouse (Peromyscus maniculatus) and Sin Nombre virus, California Channel Islands

Alteration of the wild-type (wt) p53 gene by mutation, deletion or re-arrangement is a major factor in the development of human colon cancer. Recent studies have demonstrated that p53 might be an essential component of the apoptotic pathway triggered by DNA-damaging stimuli such as chemotherapeutic agents and ionizing radiation. We examined the anti-tumor effects of adenovirus-mediated wt-p53 gene transfer in combination with a chemotherapeutic drug on the human colon cancer cell line WiDr, which is homozygous for a mutation in the p53 gene. Treatment with the chemotherapeutic drug cisplatin following infection with a replication-deficient, recombinant adenoviral vector expressing wt-p53 (termed AdCMVp53) significantly suppressed the growth of WiDr cells compared to single treatments alone. To evaluate the in vivo efficacy of AdCMVp53 and cisplatin given sequentially, WiDr cells were inoculated s.c. in nu/nu mice. After 3 days, AdCMVp53 was injected s.c. into the area where tumor cells were implanted, followed by i.p. administration of cisplatin. Analysis of initial growth inhibition at 21 days demonstrated a profound therapeutic cooperativity, though administration of either AdCMVp53 or cisplatin alone was followed only by a slowing of growth. Our results suggest that gene therapy using wt-p53-expressing adenovirus in combination with a chemotherapeutic DNA-damaging drug could be a useful strategy for treating human colon cancer.     

Reductive activation of doxorubicin by xanthine dehydrogenase from EMT6 mouse mammary carcinoma tumors

The role of enzymes in the reductive activation of various chemotherapeutic agents is an area of considerable interest in studies to better understand the selective toxicities of these agents. Xanthine dehydrogenase (XDH) is an enzyme capable of reductive activation of chemotherapeutic agents. Previously, this enzyme has not been extensively studied because of difficulties in its isolation. We recently isolated this enzyme from EMT6 mouse mammary carcinoma cells and showed that this enzyme is capable of activating mitomycin C. In this study, we examined whether XDH could activate the clinically important antineoplastic agent, doxorubicin. Drug activation was determined under aerobic and hypoxic conditions and at various pHs in order to simulate the different environments found in solid tumors. The results of these studies show that XDH reacts with doxorubicin via a two-electron reduction. This reduction is different from the modified and more extensively studied form of the enzyme, xanthine oxidase (XO), which reacts with doxorubicin via a one-electron reduction. Under hypoxic conditions, the formation of large quantities of 7-deoxydoxorubicin aglycone, a deactivation product of doxorubicin metabolism, may serve to moderate doxorubicin's antineoplastic activity. Under aerobic conditions, however, XDH activation led to a greater rate of formation of oxygen radicals than XO thereby possibly potentiating doxorubicin's cytotoxicity to aerobic tumor cells. Kinetic constants were determined for doxorubicin activation by XDH.     

Electrospray ionization mass spectrometry identification of fibrinogen Banks Peninsula (gamma280Tyr-->Cys): a new variant with defective polymerization

cis-Diamminedichloroplatinum (cisplatin) is an important anticancer drug used to treat solid tumors. The nephrotoxicity of cisplatin is recognized as the most important dose-limiting factor, but high doses of cisplatin also produce hepatotoxicity. However, little is known about cisplatin-induced liver injury and the role of metallothionein, a cysteine-rich, metal-binding protein, in modulating its hepatotoxicity. This study was designed to examine cisplatin hepatotoxicity in control and metallothionein-I/II knockout (MT-null) mice. Animals were given a single injection of cisplatin (50-200 mumol/kg i.p.), and liver injury was evaluated 3-16 h later. Cisplatin produced dose- and time-dependent liver injury, as evidenced by increased serum activity of alanine aminotransferase (ALT), as well as by histopathology. Apoptosis, rather than necrosis, predominates in cisplatin-induced liver injury, as indicated by increased numbers of apoptotic cells (hematoxylin and eosin staining), in situ apoptotic DNA detection, and DNA fragmentation on agarose gel electrophoresis. MT-null mice were more sensitive than controls to cisplatin-induced hepatotoxicity. Cisplatin (200 mumol/kg) was lethal to 12% of control mice, but 60% of MT-null mice died within 16 h. At the dose of 150 mumol/kg, serum ALT activities were increased 2-fold in control mice compared to 6.5-fold in MT-null mice. Apoptotic lesions were more pronounced in MT-null than in control mice. MT-null mice were also more susceptible than controls to cisplatin-induced nephrotoxicity, as evidenced by having higher blood urea nitrogen concentrations. Furthermore, cultured MT-null hepatocytes were more sensitive than control cells to the cytotoxicity of cisplatin (50-200 microM), as indicated by lactate dehydrogenase leakage into the medium. These results demonstrate that (1) high doses of cisplatin produce hepatotoxicity, with apoptosis as the major lesion, and (2) MT protects against cisplatin-induced liver injury.     

Tyrphostin 4-nitrobenzylidene malononitrile reduces chemotherapy toxicity without impairing efficacy

In mice, 4-nitrobenzylidene malononitrile (AG1714), which belongs to the tyrphostin family, reduced toxicity induced by doxorubicin and cisplatin without impairing their antitumor efficacy. AG1714 reduced mortality induced by doxorubicin and cisplatin. It prevented, in a dose-dependent manner, cisplatin-induced nephrotoxicity as assessed by measurement of serum creatinine and blood urea nitrogen levels. The protective effect of AG1714 was most pronounced on its administration 2 h before cisplatin. AG1714 also prevented doxorubicin-induced myelosuppression as assessed by the scoring of bone marrow nucleated cells and colony-forming units. Cisplatin-induced small intestinal injury was also protected by AG1714 as assessed by histopathological analysis. In vitro, AG1714 reduced cisplatin-induced apoptosis in a murine fibroblastic cell line (A9) and did not affect doxorubicin-induced apoptosis of B-16 melanoma cells. In contrast to its protective effect against mortality and injury of normal tissues induced by chemotherapy, AG1714 did not impair its antitumor activity and in some tumor models enhanced it. This was evident by using the murine tumors B-16 melanoma, Lewis lung carcinoma, and methylcholanthrene-induced fibrosarcoma and the human tumors SK-28 melanoma and human ovary carcinoma xenografts in nude mice. Experiments in which low and high doses of cisplatin and doxorubicin were administered to tumor-bearing mice demonstrated that AG1714 reduced mortality of high-dose chemotherapy and increased its therapeutic index. AG1714 could provide a novel, useful tool to improve chemotherapy by allowing dose intensification.     

Unusual patellar tendon injury in an adolescent runner with generalised ligamentous laxity

Gemcitabine, a novel pyrimidine nucleoside antimetabolite, has shown clinical antitumor activity against several tumors (breast, small-cell and non-small-cell lung, bladder, pancreatic, and ovarian). We have developed a drug-resistance profile for gemcitabine using eight drug-resistant P388 leukemias in order to identify potentially useful guides for patient selection for further clinical trials of gemcitabine and possible noncrossresistant drug combinations with gemcitabine. Multidrug-resistant P388 leukemias (leukemias resistant to doxorubicin or etoposide) exhibited no crossresistance to gemcitabine. Leukemias resistant to vincristine (not multidrug resistant), cyclophosphamide, melphalan, cisplatin, and methotrexate were also not crossresistant to gemcitabine. Only the leukemia resistant to 1-beta-D-arabinofuranosylcytosine was crossresistant to gemcitabine. The results suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with 1-beta-D-arabinofuranosylcytosine and (2) the lack of crossresistance seen with gemcitabine may contribute to therapeutic synergism when gemcitabine is combined with other agents.     

Modulation of ras p21 oncoprotein levels and DNA strand breakage in human cells with chemotherapeutic agents and/or deferoxamine

Oncogenes are involved with the regulation of cellular proliferation. Ras oncogenes can be activated by chemical treatment and any increased activity could be modulated by further chemical treatment. In the present study, therefore, ras p21 protein expression was examined in in vitro cultures of human lymphocytes treated with mitomycin C and in the human colon adenocarcinoma Caco-2 cell line treated with doxorubicin with and without deferoxamine. Both chemotherapeutic agents act partially through oxygen radical mechanisms. Increases in p21 protein levels were seen with mitomycin C but no clear response was seen with doxorubicin. However, deferoxamine, with and without doxorubicin, altered p21 expression. Deferoxamine is an iron chelator so these results support the hypothesis that oxygen radicals were responsible for the altered p21 protein levels. Modulating responses were confirmed by measuring DNA strand-breakage in the Comet assay after treatment with doxorubicin and deferoxamine. Alterations of ras p21 protein expression in vitro might prove a suitable system for examining modulating effects on chemical carcinogens.     

Resistance to chemotherapeutic antimetabolites: a function of salvage pathway involvement and cellular response to DNA damage

The inherent or acquired (induced) resistance of certain tumours to cytotoxic drug therapy is a major clinical problem. There are many categories of cytotoxic agent: the antimetabolites, e.g. methotrexate (MTX), N-phosphonacetyl-L-aspartate (PALA), 5-fluorouracil (5-FU), 6-mercaptopurine (6-TG), hydroxyurea (HU) and 1-beta-D-arabinofuranosylcytosine (AraC); the alkylating agents, e.g. the nitrogen mustards and nitrosoureas; the antibiotics, e.g. doxorubicin and mitomycin C; the plant alkaloids, e.g. vincristine and vinblastine; and miscellaneous compounds, such as cisplatin. There are also many mechanisms of drug resistance elucidated principally from in vitro studies. These include mutation of target genes, amplification of target and mutated genes, differences in repair capacity, altered drug transport and differences in nucleoside and nucleobase salvage pathways (Fox et al, 1991). The aim of the present review is to evaluate in detail the mechanisms of response of both normal and tumour cells to three chemotherapeutic antimetabolites, MTX, PALA and 5-FU, which are routinely used in the clinic either alone or in combination to treat some of the commonest solid tumours, e.g. breast, colon, gastric and head and neck. The normal and tumour cell response to these agents will be discussed in relation to the operation of the known alternative 'salvage pathways' of DNA synthesis and current theories of DNA damage response.     

Intraarterial hepatic chemotherapy with fluorouracil, fluorodeoxyuridine, mitomycin C, cisplatin or methotrexate as single-agent anticancer drugs for a transplanted experimental liver tumor in rats

A prospective, controlled and standardized animal experiment was performed to study the influence of various anticancer drugs. The Novikoff hepatoma transplanted into male Sprague-Dawley rats was treated with fluorouracil (FUra), mitomycin C, methotrexate, cisplatin and fluorodeoxyuridine (FdUrd) at equi-effective dosage, in terms of side effects (weight loss), in comparison to a control group (0.9% saline solution) by locoregional application via the hepatic artery. The tumor multiplication factor (TMF = tumor volume day 12/tumor volume day 5) served as the parameter to compare the tumor growth of the various groups. All drugs showed a significant (P < 0.05) effect on the tumor growth. In comparison to the control group (mean TMF 9.66), FdUrd (3.78) and FUra (3.03) only limited the tumor growth, mitomycin C (0.96) produced stable tumor, cisplatin (0.64) and methotrexate (0.15) significantly reduced (P < 0.01) the tumor size. We suggest that, in addition to the established (FUra, FdUrd, mitomycin C) drugs, methotrexate and cisplatin should be considered in further studies of the treatment of primary and secondary liver malignancies.     

sst2 somatostatin receptor expression reverses tumorigenicity of human pancreatic cancer cells

Among the five cloned somatostatin receptor subtypes (sst1 to sst5), sst2 mediates the antiproliferative effect of somatostatin analogues in vitro. Somatostatin analogues have been shown to inhibit cell growth in vitro and in vivo in pancreatic cancer models that expressed sst2. We recently demonstrated the loss of sst2 gene expression in human pancreatic adenocarcinomas and most of the derived pancreatic cancer cell lines. In the present study, we corrected the sst2 defect in human pancreatic cancer BxPC-3 and Capan-1 cells by stable transfection with human sst2 cDNA. In the absence of exogenous ligand, both BxPC-3 and Capan-1 cells expressing sst2 showed a significant reduction in cell growth. This inhibitory effect was blocked by treatment with antiserum to somatostatin. sst2-expressing cells produced somatostatin-like immunoreactivity that mainly corresponded to somatostatin 14, indicating the induction of a negative autocrine loop. In other respects, sst2 expression in Capan-1 cells induced a significant reduction of clonogenicity in soft agar. Moreover, a significantly reduced (Capan-1 cells) or suppressed (BxPC-3 cells) tumor growth in athymic nude mice was observed. The reversal of tumorigenicity induced by the restoration of sst2 expression suggests that the loss of sst2 contributes to the malignancy of human pancreatic cancers.     

A canalicular multispecific organic anion transporter (cMOAT) antisense cDNA enhances drug sensitivity in human hepatic cancer cells

The human cMOAT gene encodes a membrane protein involved in the ATP-dependent transport of hydrophobic compounds. To determine whether cMOAT is associated with drug sensitivity, we transfected an expression vector containing cMOAT antisense cDNA into the HepG2 human hepatic cancer cell line. We observed a reduction in cMOAT protein, as well as an enhanced level of glutathione, in the antisense transfectants. The transfectants displayed an increased sensitivity to cisplatin, vincristine, doxorubicin, and the camptothecin derivatives, (4S)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)carbonyl oxy]dione hydrochloride triethydrate and 7-ethyl-10-hydroxycamptothecin, but not to etoposide, 3-[4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosoure a, 5-fluorouracil, and mitomycin C. Results suggest that cMOAT levels are inversely correlated with those of glutathione, and that cMOAT and its related genes may be involved in the sensitivity of cells to certain anticancer agents.     

Synergistic cytotoxicity of bcl-2 antisense oligodeoxynucleotides and etoposide, doxorubicin and cisplatin on small-cell lung cancer cell lines

Expression of Bcl-2 is life-sustaining for small-cell lung cancer cells and associated with drug resistance. In the present study, the interactions between the bcl-2 antisense oligodeoxynucleotide 2009 and the chemotherapeutic agents etoposide, doxorubicin and cisplatin were investigated on small-cell lung cancer cell lines to search for synergistic combinations. The cell lines NCI-H69, SW2 and NCI-H82 express high, intermediate-high and low basal levels of Bcl-2, respectively, which are inversely correlated with the sensitivities of the cell lines to treatment with oligodeoxynucleotide 2009 and the chemotherapeutic agents alone. Moreover, differences were found in the responsiveness of the cell lines to treatment with combinations of oligodeoxynucleotide 2009 and the chemotherapeutic agents. In the cell lines NCI-H69 and SW2, all combinations resulted in synergistic cytotoxicity. In NCI-H69 cells, maximum synergy with a combination index of 0.2 was achieved with the combination of oligodeoxynucleotide 2009 and etoposide. In SW2 cells, the combination of oligodeoxynucleotide 2009 and doxorubicin was the most effective (combination index = 0.5). In the cell line NCI-H82, which expresses a low basal level of Bcl-2, most of the combinations were slightly antagonistic. Our data suggest the use of oligodeoxynucleotide 2009 in combination with chemotherapy for the treatment of small-cell lung cancer that overexpresses Bcl-2.     

bcl-2 antisense therapy chemosensitizes human melanoma in SCID mice

Malignant melanoma is a prime example of cancers that respond poorly to various treatment modalities including chemotherapy. A number of chemotherapeutic agents have been shown recently to act by inducing apoptosis, a type of cell death antagonized by the bcl-2 gene. Human melanoma expresses Bcl-2 in up to 90% of all cases. In the present study we demonstrate that bcl-2 antisense oligonucleotide treatment improves the chemosensitivity of human melanoma grown in severe combined immunodeficient (SCID) mice. Our findings suggest that reduction of Bcl-2 in melanoma, and possibly also in a variety of other tumors, may be a novel and rational approach to improve chemosensitivity and treatment outcome.