Immunocytochemical detection of tumor cells in bone marrow and peripheral blood stem cell collections from patients with ovarian cancer.

High-dose chemotherapy (HDC) followed by autologous hematopoietic reconstitution is an experimental treatment option for patients with epithelial ovarian cancer. However, the incidence of occult ovarian tumor cell involvement in autologous bone marrow (BM) or peripheral blood stem cell (PBSC) autografts has not been widely investigated. We used a highly sensitive immunocytochemical (ICC) procedure that detects occult blood-borne tumor micrometastases. We analyzed 24 BM specimens (15 obtained during therapy and 9 harvest samples) and seven PBSC specimens from 22 patients with ovarian cancer. Overall, ICC analysis detected immunostained tumor cells in 10 of 23 evaluable BM specimens (43%) from 9 of 19 patients (47%). One of 9 (11%) harvest samples contained tumor cells. Only one of the 10 ICC-positive BM specimens had tumor cells detected by routine histopathological analysis. ICC-detectable tumor cells were cleared from the marrow of two patients during chemotherapy. None of the seven PBSC specimens contained tumor cells. We conclude that ovarian cancer micrometastases have the potential to contaminate BM, as is also the case in patients with other epithelial malignancies. In the limited number of specimens analyzed, PBSC harvests appeared to provide a less tumor-contaminated source of hematopoietic stem cells for autologous transplantation.

Evaluation of in vitro drug screening leads using experimental models of human ovarian cancer.

Five compounds which were identified as potential new anticancer drugs in in vitro screening with the human tumor colony forming assay were selected for further evaluation using in vitro and in vivo models of human ovarian cancer. Three of five compounds were found to inhibit in vitro colony formation of ovarian cancer cell lines derived from both untreated and combination chemotherapy refractory patients. One compound was also found to prolong survival in a human ovarian carcinoma xenograft model system. This compound, chloroquinoxaline sulfonamide, was selected for development and has shown preliminary indication of activity in phase I clinical testing.

Characterization of a cis-diamminedichloroplatinum(II)-resistant human ovarian cancer cell line and its use in evaluation of platinum analogues.

Human ovarian cancer cell lines with stable cisplatin resistance have been developed by chronic exposure of the parent cisplatin-sensitive A2780 line to increasing concentrations of cisplatin. 2780CP8 (CP8 refers to this cell line's growth in medium containing 8 microM cisplatin) has several clonal cytogenetic abnormalities but lacks homogeneously staining regions or double-minute chromosomes. It has a significantly greater monolayer growth rate, cloning efficiency in agarose, and total glutathione content compared to the A2780 line, but similar activities of several glutathione-dependent enzymes. The 2780CP8 subline is 7.3-fold resistant to cisplatin compared to the A2780 line, as well as cross-resistant to irradiation and melphalan. It is not cross-resistant to Adriamycin, but this develops with increased cisplatin resistance (14-fold) obtained by further cisplatin exposure of 2780CP8. Of the cisplatin analogues tested which are of current clinical interest, carboplatin, iproplatin, and tetraplatin, only the latter is more cytotoxic than cisplatin in the A2780 and 2780CP8 lines. The 2780CP8 subline is also cross-resistant to these analogues in the relative order carboplatin greater than iproplatin greater than tetraplatin (most to least cross-resistant). Treatment of a highly cisplatin resistant cell line (2780CP70) with either melphalan or cisplatin was associated with a significant increase in [3H]thymidine incorporation into DNA in the presence of 10 mM hydroxyurea compared with the parent sensitive cell line which showed essentially no capacity to repair DNA damage by these drugs. A2780 and its cisplatin-resistant cell lines may thus be useful in studying drug resistance mechanisms, in screening new drugs for activity (especially against drug resistant tumors), and in formulating induction and salvage therapies for ovarian cancer.

Enhanced melphalan cytotoxicity in human ovarian cancer in vitro and in tumor-bearing nude mice by buthionine sulfoximine depletion of glutathione.

The development of acquired resistance to alkylating agents frequently limits the effectiveness of chemotherapy in the treatment of ovarian cancer. While the resistance to alkylating agents is multifactorial, the association of drug resistance with elevations in glutathione (GSH) is of potential clinical relevance since there exist pharmacologic means to lower intracellular GSH levels. We have used in vitro and in vivo models of human ovarian cancer to demonstrate that selective inhibition of GSH synthesis with L-buthionine-S,R-sulfoximine (L-BSO) leads to a lowering of GSH levels and an increase in cytotoxicity of the alkylating agent melphalan. In the human ovarian cancer cell line NIH:OVCAR-3, derived from a patient clinically refractory to alkylating agents, L-BSO resulted in a 3.6-fold enhancement of melphalan cytotoxicity. This cell line was also adapted for intraperitoneal growth in athymic nude mice. In this in vivo model, in which the mice die of massive ascites and intraabdominal carcinomatosis, L-BSO given orally in drinking water for 5 days decreased GSH levels in the tumor cells by 96% compared to a 79 and 86% reduction in GSH levels in the bone marrow and gastrointestinal mucosa respectively. Lowering of GSH levels with BSO was not accompanied by an increase in lethality for melphalan in non-tumored nude mice. However, in tumor-bearing nude mice, a single melphalan (5 mg/kg) treatment following GSH depletion with L-BSO was markedly superior to treatment with melphalan alone, producing a 72% increase in median survival time. Furthermore, L-BSO treatment of human bone marrow cells prior to melphalan exposure had little effect on melphalan toxicity as assessed in a CFUc-GM assay. These results suggest that treatment with the GSH synthesis inhibitor BSO may preferentially enhance the cytotoxic effects of alkylating agents against human ovarian cancer and overcome acquired resistance.

Long-term results of a cisplatin-containing combination chemotherapy regimen for the treatment of advanced ovarian carcinoma.

Sixty-two patients with advanced ovarian adenocarcinoma (stages III and IV) and without prior chemotherapy or radiotherapy were treated with a four-drug combination consisting of cyclophosphamide, hexamethylmelamine, 5-fluorouracil (5-FU), and cisplatin (Chex-UP). All patients were evaluable for toxicity and response, and survivors have been observed for a minimum of 48 months. The overall response rate to Chex-UP chemotherapy was 69%, with 12 patients (19%) achieving a pathologically confirmed complete remission (CR) as documented by a negative second-look laparotomy. Seven of the twelve patients (58%) who achieved a surgically confirmed CR were randomized to six cycles of intraperitoneal (IP) 5-FU. There have been seven relapses in patients who had a negative second-look laparotomy, but only four of the patients died from recurrent ovarian cancer. The median duration of remission following a negative second-look laparotomy was 53 months, while the median duration of survival has not been reached and will exceed 7.5 years. Seventeen patients (27%) achieved a clinical CR with chemotherapy but were found to have residual disease at second-look laparotomy. The median survival for these patients was 29 months, which was statistically inferior to that achieved for those patients with a negative second-look laparotomy (P less than .002), and only one patient is alive after 4 years. All patients who either achieved a partial response (PR) to therapy (14 of 62; 23%) or did not respond to therapy (19 of 62; 31%) died of ovarian cancer by 24 months. Thus, prolonged survival is associated with a surgically confirmed CR to induction therapy with Chex-UP. However, only a minority of advanced-stage ovarian cancer patients (15%) are alive 4 years after initiation of treatment with this regimen.

Collateral susceptibility of adriamycin-, melphalan- and cisplatin-resistant human ovarian tumor cells to bleomycin.

Three cell lines resistant to adriamycin, melphalan and cisplatin were established in vitro from human ovarian cancer cell line A2780. Each subline showed a resistance to its inducing drug of 75-fold in the case of adriamycin, 6-fold in the case of melphalan and 11-fold in the case of cisplatin. However, all of these sublines showed collateral sensitivity to bleomycin. Approximately a 2-fold higher susceptibility to bleomycin was observed generally. The biochemical mechanisms of this collateral sensitivity are not clear at present, but the higher concentration of glutathione in these resistant tumor cell lines might be related to the high susceptibility of these resistant cells to bleomycin.

Adriamycin accumulation and metabolism in adriamycin-sensitive and -resistant human ovarian cancer cell lines.

Adriamycin accumulation and metabolism were studied in three distinct groups of human ovarian cancer cell lines: those derived from previously untreated patients, those from clinically refractory (relapsed) patients, and those with induced resistance to adriamycin in vitro. The 2-hr [14C] adriamycin accumulation in cell lines from previously untreated patients (A2780 and A1847 [Eva et al., Nature, Lond. 295, 116 (1982)] and OVCAR-5 [National Institutes of Health human OVarian CAR-cinoma cell line no. 5]) was 11-14 ng/10(6) cells. 2780AD and 1847AD (variants with in vitro induced resistance to adriamycin) accumulated one-third as much adriamycin after 2 hr (4 ng/10(6) cells). However, three cell lines derived from clinically refractory patients accumulated the same amount of adriamycin as cell lines from untreated patients (8-13 ng/10(6) cells). A high-performance liquid chromatography (HPLC) assay for adriamycin and its analogs confirmed these results and demonstrated only parent drug (no metabolites) in any of the cell lines tested. These results demonstrate that the primary mechanism of adriamycin resistance in some ovarian cancer cells from clinically refractory patients is not enhanced metabolism of drug or a transport defect leading to a decreased net accumulation such as has been described for cells with in vitro induced resistance to adriamycin.

Preclinical evaluation of aclacinomycin A for the intraperitoneal treatment of human ovarian carcinoma.

Combination chemotherapy regimens have produced a pathological complete response rate of only 1%-25% in patients with advanced ovarian cancer. Patients with small-volume residual disease after treatment are refractory to further systemic therapy, and most eventually die of their disease. Intraperitoneal (i.p.) chemotherapy, particularly with adriamycin or cisplatin has shown promise in these patients. However, the dose-limiting painful peritonitis associated with i.p. adriamycin makes this regimen potentially too toxic for many patients. Aclacinomycin A, another anthracycline antibiotic, has been found to have activity against a wide variety of murine tumors and human xenografts. It has also demonstrated clinical efficacy in phase I and II trials against refractory ovarian cancer and has less pronounced vesicant properties than adriamycin, making it an ideal candidate for i.p. use in ovarian cancer patients. In vitro clonogenic assays utilizing a battery of adriamycin-sensitive and -resistant human ovarian carcinoma cell lines have shown that aclacinomycin A is more cytotoxic than adriamycin in all cell lines tested. In addition, aclacinomycin A was found to prolong survival in a nude mouse xenograft of i.p. human ovarian cancer. These results have provided the experimental rationale for an ongoing clinical trial of i.p. aclacinomycin in refractory ovarian cancer patients at the Medicine Branch, NCI.

Activity of tricyclic nucleoside 5'-phosphate in model systems of human ovarian cancer.

Tricyclic nucleoside 5'-phosphate (TCN-P) was evaluated in two models of human ovarian cancer. TCN-P reduced both colony number and volume in clonogenic assays employing human ovarian cancer cell lines. TCN-P cytotoxicity depended on the concentration, exposure duration and cell line studied, but not on cell line plating efficiency or growth rate in soft agarose. Comparison of experimental IC50 concentrations for 1 hour or continuous TCN-P exposure with reported clinically relevant concentrations suggests that therapeutic TCN-P levels are more likely to be achieved by continuous infusions. Cell lines and sublines with resistance to several standard chemotherapeutic agents acquired both in vivo and in vitro were at most 2.6-fold cross-resistant to TCN-P with 1 hour drug exposure. Cross-resistance was not evident with continuous TCN-P exposure. Intermittent bolus TCN-P (100 mg/kg/d X 5) was ineffective in an in vivo xenograft model of human ovarian cancer. These data suggest that TCN-P is most likely to be clinically effective against ovarian cancer, and may be non-cross-resistant with several standard agents, if administered by continuous infusion. Preclinical evaluation of new agents, such as TCN-P, in these experimental models may provide information useful in subsequent clinical trials.

Radiation survival parameters of antineoplastic drug-sensitive and -resistant human ovarian cancer cell lines and their modification by buthionine sulfoximine.

The optimum integration of chemotherapy and irradiation is of potential clinical significance in the treatment of ovarian cancer. A series of human ovarian cancer cell lines have been developed in which dose-response relationships to standard anticancer drugs have been determined, and the patterns of cross-resistance between these drugs and irradiation have been established. By stepwise incubation with drugs, sublines of A2780, a drug-sensitive cell line, have been made 100-fold, 10-fold, and 10-fold more resistant to Adriamycin (2780AD), melphalan (2780ME), and cisplatin (2780CP). Two additional cell lines, NIH:OVCAR-3nu(Ag+) and NIH:OVCAR-4(Ag+), were established from drug-refractory patients. 2780ME, 2780CP, OVCAR-3nu(Ag+), and OVCAR-4(Ag+) are all cross-resistant to irradiation, with DOS of 146, 187, 143, and 203, respectively. However, 2780AD remains sensitive to radiation, with a DO of 111, which is similar to that of A2780 (101). Glutathione (GSH) levels are elevated in 2780ME, 2780CP, OVCAR-3nu(Ag+), and OVCAR-4(Ag+) to 4.58, 6.13, 12.10, and 15.14 nmol/10(6) cells as compared to A2780, with 1.89 nmol/10(6) cells. However, the GSH level in 2780AD is only minimally higher than that in A2780 (2.94 nmol/10(6) cells). Buthionine sulfoximine, a specific inhibitor of GSH synthesis, significantly increases the radiation sensitivity of 2780ME (changing the DO from 143 to 95) and 2780CP to a lesser extent, suggesting that intracellular GSH levels may play an important role in the radiation response of certain neoplastic cells. These results suggest that the sequential use of irradiation following chemotherapy with melphalan and cisplatin may be less effective than a combined modality approach, which integrates radiation and chemotherapy prior to the development of drug resistance and cross-resistance to irradiation.

Characterization of a xenograft model of human ovarian carcinoma which produces ascites and intraabdominal carcinomatosis in mice.

We have used in vivo and in vitro procedures to select a subpopulation of cells from the human ovarian carcinoma cell line, NIH:OVCAR-3, with the capacity to grow i.p. in female nude athymic mice. After i.p. injection of these cells, animals develop metastatic spread similar to that of clinical ovarian cancer. Disease progression is characterized by the development of massive ascites, extensive invasive i.p. tumors, and pulmonary metastases. The malignant ascites cells are transplantable, manifest cytoplasmic androgen and estrogen receptors, and express the ovarian cancer associated antigen CA125 (116,000 units/ml of ascites supernatant). The cells also have the same chromosome markers which were present in the original cell line, NIH:OVCAR-3. Survival following i.p. passage of ascites is dependent on tumor cell inoculum ranging from a median survival of 39 days with 40 million cells to 84 days for 11.5 million transplanted cells. The characteristics of this unique in vivo model make it well suited for the evaluation of new drugs and novel experimental therapies in ovarian cancer. In addition, this in vivo model, together with ovarian cancer cell lines, may prove particularly useful for the study of pharmacological ways to specifically increase the cytotoxicity of anticancer agents in tumor cells while not increasing toxicity in normal tissues. The presence of hormone receptors should facilitate the experimental evaluation of hormonal therapy in ovarian cancer.

Induction of progesterone receptor with 17 beta-estradiol in human ovarian cancer.

We utilized a xenograft model of human ovarian cancer to study the ability of estrogen to induce progesterone receptor. Tumor cytosol from 17 beta-estradiol treated oophorectomized animals, but not oophorectomized controls, contained a [3H]ORG 2058 binding moiety of sedimentation coefficient 6-9S. This component showed specificity for the progestagens: progesterone, ORG 2058, and R5020 and for the antiprogestagen cyproterone acetate. At 1000-fold molar excess, 5 alpha-dihydrotestosterone competed partially for these sites while diethylstilbestrol, dexamethasone, and the antiandrogen, SCH 16423, were ineffective competitors. The dissociation constant for this progestagen binding entity was 0.14 nM using [3H]ORG 2058 as labeled ligand and R5020 as competitor. In addition, saturation analysis demonstrated that approximately 400 fmol of progestagen specific binding capacity was available per mg of cytosol protein. These data suggest that estrogen can induce progesterone receptor in human ovarian carcinoma.