A phase I trial of paclitaxel, cisplatin, and veliparib in the treatment of persistent or recurrent carcinoma of the cervix: an NRG Oncology Study (NCT#01281852).

Background: Preclinical studies demonstrate poly(ADP-ribose) polymerase (PARP) inhibition augments apoptotic response and sensitizes cervical cancer cells to the effects of cisplatin. Given the use of cisplatin and paclitaxel as first-line treatment for persistent or recurrent cervical cancer, we aimed to estimate the maximum tolerated dose (MTD) of the PARP inhibitor veliparib when added to chemotherapy. Patients and methods: Women with persistent or recurrent cervical carcinoma not amenable to curative therapy were enrolled. Patients had to have received concurrent chemotherapy and radiation as well as possible consolidation chemotherapy; have adequate organ function. The trial utilized a standard 3 + 3 phase I dose escalation with patients receiving paclitaxel 175 mg/m2 on day 1, cisplatin 50 mg/m2 on day 2, and escalating doses of veliparib ranging from 50 to 400 mg orally two times daily on days 1-7. Cycles occurred every 21 days until progression. Dose-limiting toxicities (DLTs) were assessed at first cycle. Fanconi anemia complementation group D2 (FANCD2) foci was evaluated in tissue specimens as a biomarker of response. Results: Thirty-four patients received treatment. DLTs (n = 1) were a grade 4 dyspnea, a grade 3 neutropenia lasting ≥3 weeks, and febrile neutropenia. At 400 mg dose level (DL), one of the six patients had a DLT, so the MTD was not reached. Across DLs, the objective response rate (RR) for 29 patients with measurable disease was 34% [95% confidence interval (CI), 20%-53%]; at 400 mg DL, the RR was 60% (n = 3/5; 95% CI, 23%-88%). Median progression-free survival was 6.2 months (95% CI, 2.9-10.1), and overall survival was 14.5 months (95% CI, 8.2-19.4). FANCD2 foci was negative or heterogeneous in 31% of patients and present in 69%. Objective RR were not associated with FANCD2 foci (P = 0.53). Conclusions: Combining veliparib with paclitaxel and cisplatin as first-line treatment for persistent or recurrent cervical cancer patients is safe and feasible. Clinical trial information: NCT01281852.

Phase I study of biweekly oxaliplatin, gemcitabine and capecitabine in patients with advanced upper gastrointestinal malignancies.

BACKGROUND: Oxaliplatin, gemcitabine and capecitabine are all active agents against upper gastrointestinal and pancreaticobiliary cancers. PATIENTS AND METHODS: Patients with upper gastrointestinal malignancies treated with 0-2 prior chemotherapy regimens received oxaliplatin (85-100 mg/m(2)) as a 2-h i.v. infusion with gemcitabine (800-1000 mg/m(2)) at a constant rate i.v. infusion (CI) of 10 mg/m(2)/min on days 1 and 15 of a 28-day cycle. Capecitabine (600-800 mg/m(2)) was administered orally twice a day on days 1-7 and 15-21. A three per cohort dose escalation schema was used to determine the maximum tolerated dose (MTD) and the dose-limiting toxic effects (DLTs) of this combination regimen. RESULTS: Thirty patients with advanced upper gastrointestinal malignancies were enrolled. The MTD was defined as oxaliplatin 100 mg/m(2) i.v. over 2 h plus gemcitabine 800 mg/m(2) i.v. at a CI of 10 mg/m(2)/min on days 1 and 15 with capecitabine 800 mg/m(2) p.o. b.i.d. days 1-7 and 15-21 of a 29-day cycle. DLTs include grade 3 fatigue and grade 3 dyspnea. One complete and two partial responses were observed. CONCLUSIONS: This biweekly schedule of oxaliplatin, gemcitabine and capecitabine is tolerable and warrants further investigation in biliary and pancreatic malignancies.

Phase I study of pegylated liposomal doxorubicin and the multidrug-resistance modulator, valspodar.

Valspodar, a P-glycoprotein modulator, affects pharmacokinetics of doxorubicin when administered in combination, resulting in doxorubicin dose reduction. In animal models, valspodar has minimal interaction with pegylated liposomal doxorubicin (PEG-LD). To determine any pharmacokinetic interaction in humans, we designed a study to determine maximum tolerated dose, dose-limiting toxicity (DLT), and pharmacokinetics of total doxorubicin, in PEG-LD and valspodar combination therapy in patients with advanced malignancies. Patients received PEG-LD 20-25 mg m(-2) intravenously over 1 h for cycle one. In subsequent 2-week cycles, valspodar was administered as 72 h continuous intravenous infusion with PEG-LD beginning at 8 mg m(-2) and escalated in an accelerated titration design to 25 mg m(-2). Pharmacokinetic data were collected with and without valspodar. A total of 14 patients completed at least two cycles of therapy. No DLTs were observed in six patients treated at the highest level of PEG-LD 25 mg m(-2). The most common toxicities were fatigue, nausea, vomiting, mucositis, palmar plantar erythrodysesthesia, diarrhoea, and ataxia. Partial responses were observed in patients with breast and ovarian carcinoma. The mean (range) total doxorubicin clearance decreased from 27 (10-73) ml h(-1) m(-2) in cycle 1 to 18 (3-37) ml h(-1) m(-2) with the addition of valspodar in cycle 2 (P=0.009). Treatment with PEG-LD 25 mg m(-2) in combination with valspodar results in a moderate prolongation of total doxorubicin clearance and half-life but did not increase the toxicity of this agent.

Phase I study of rubitecan and gemcitabine in patients with advanced malignancies.

BACKGROUND: Rubitecan (9-nitrocamptothecin, 9-NC, Orathecin) and gemcitabine have single-agent activity in pancreatic and ovarian carcinoma. We conducted a phase I trial to evaluate the maximum tolerated dose (MTD) and toxicities of this combination in advanced malignancies. PATIENTS AND METHODS: Twenty-one patients with refractory or recurrent malignancies were enrolled in this dose escalation trial. Dose escalation proceeded from a starting level of rubitecan at 0.75 mg/m(2)/day administered orally on days 1-5 and 8-12 in combination with gemcitabine 1000 mg/m(2) administered intravenously on days 1 and 8 of a 21-day cycle. RESULTS: The MTD was defined as rubitecan 1 mg/m(2) administered orally days 1-5 and 8-12, and gemcitabine 1000 mg/m(2) administered intravenously over 30 min days 1 and 8, given every 21 days. Dose-limiting toxicity was myelosuppression including neutropenia and thrombocytopenia. Other side effects included diarrhea, nausea, vomiting and fatigue. Five patients with stable disease were observed among 18 evaluable patients. CONCLUSIONS: The recommended phase II dose is rubitecan 1 mg/m(2) given orally on days 1-5 and 8-12 in combination with gemcitabine 1000 mg/m(2) as a 30-min intravenous infusion on days 1 and 8 of a 21-day cycle.

Phase II study of paclitaxel and valspodar (PSC 833) in refractory ovarian carcinoma: a gynecologic oncology group study.

PURPOSE: A phase II study was conducted to determine the efficacy of paclitaxel and valspodar (PSC 833) in patients with advanced epithelial ovarian cancer. Valspodar, a nonimmunosuppressive cyclosporine D analogue that reverses P-glycoprotein-mediated multidrug resistance, in combination with paclitaxel might be active in paclitaxel-resistant and refractory ovarian cancer. PATIENTS AND METHODS: Patients received valspodar 5 mg/kg orally qid x 12 doses. Paclitaxel (70 mg/m(2) intravenously for 3 hours) was administered on day 2, 2 hours after the fifth or sixth dose of valspodar. This treatment was repeated every 21 days. One blood sample was collected before the sixth dose of valspodar for the first three cycles to evaluate valspodar trough concentration. Tumor tissue was obtained from patients for immunohistochemical staining of P-glycoprotein. RESULTS: Of 60 patients entered, 58 were assessable for response. There were five partial responses (8.6%; 90% confidence interval [CI], 3.8 to 20.0; median duration of response, 5.0 months [range, 1.9 to 10.5 months]). Median progression-free survival was 1.5 months (90% CI, 1.4 to 2.4). Grade 3 or 4 toxicities observed were neutropenia, anemia, nausea and vomiting, peripheral neuropathy, and cerebellar ataxia. The trough concentrations of valspodar were > or = 1,000 ng/mL in all but two of 40 patients in the first cycle. Immunohistochemical staining for P-glycoprotein was positive for one of two responding patients. CONCLUSION: Valspodar in combination with paclitaxel has limited activity in patients with paclitaxel-resistant ovarian carcinoma. An international randomized clinical trial of paclitaxel and carboplatin with or without valspodar as first-line therapy in advanced ovarian cancer is underway.

Phase I trial of escalating doses of paclitaxel combined with fixed doses of cisplatin and doxorubicin in advanced endometrial cancer and other gynecologic malignancies: a Gynecologic Oncology Group study.

PURPOSE: The primary objective of this phase I trial was to determine the feasibility of administering a combination of paclitaxel, cisplatin, and doxorubicin with or without granulocyte colony-stimulating factor (G-CSF) in patients with advanced endometrial and other gynecologic cancers. PATIENTS AND METHODS: Patients were chemotherapy-naive. Doxorubicin was administered as a brief infusion, paclitaxel for 3 hours, and cisplatin for 60 minutes. Treatments were repeated every 3 weeks. For most dose levels, the cisplatin and doxorubicin were fixed at 60 mg/m(2) and 45 mg/m(2), whereas the paclitaxel was escalated in successive cohorts from 90 to 250 mg/m(2). Patients who had received previous radiotherapy to the whole pelvis were escalated separately from those who had not. RESULTS: Eighty patients received 320 cycles of therapy. When G-CSF was not used, myelosuppression prevented escalation beyond the starting dose for patients with or without previous pelvic radiotherapy. When G-CSF was added, neurotoxicity became dose-limiting for both groups. Ten patients were removed from the study for asymptomatic declines in ejection fraction, but no symptomatic congestive heart failure was observed. Major antitumor responses occurred in 46% of patients (six of 13) with measurable endometrial carcinoma and 50% of patients (eight of 16) with measurable cervical carcinoma. CONCLUSION: The combination of paclitaxel, doxorubicin, and cisplatin at relevant single-agent doses is active and feasible with the addition of G-CSF. A regimen of cisplatin 60 mg/m(2), doxorubicin 45 mg/m(2), and paclitaxel 160 mg/m(2) with G-CSF support is recommended for further testing.

Overcoming drug resistance in ovarian carcinoma.

Advanced epithelial ovarian carcinoma is treated with cytoreductive surgery and combination chemotherapy with a platinum compound and paclitaxel. Despite this treatment strategy, most women eventually relapse and die of resistant disease. Preclinical studies have shown that alterations in drug accumulation, drug metabolism, DNA repair, cellular targets and/or cell survival pathways may cause this resistance. Clinical studies have employed modulators of resistance in combination with chemotherapy as a means to overcome drug resistance. The most extensively studied modulators, buthionine sulfoximine and valspodar, are involved in reversing resistance caused by glutathione and P-glycoprotein, respectively. A phase III study comparing paclitaxel and carboplatin with and without valspodar is ongoing. However, other approaches to overcoming drug resistance are necessary for the effective treatment of women with this disease.

Phase I dose-finding and pharmacokinetic study of paclitaxel and carboplatin with oral valspodar in patients with advanced solid tumors.

PURPOSE: To evaluate the maximum-tolerated dose (MTD), dose-limiting toxicities (DLTs), and pharmacokinetic (PK) profile of paclitaxel and carboplatin when administered every 3 weeks with the oral semisynthetic cyclosporine analog valspodar (PSC 833), an inhibitor of P-glycoprotein function. PATIENTS AND METHODS: Fifty-eight patients were treated with escalating doses of paclitaxel ranging from 54 to 94.5 mg/m(2) and carboplatin area under the plasma concentration versus time curve (AUC) ranging from 6 to 9 mg.min/mL, every 21 days. The dose of valspodar was fixed at 5 mg/kg every 6 hours for a total of 12 doses from day 0 to day 3. The MTD was determined for the following two groups: (1) previously treated patients, where paclitaxel and carboplatin doses were escalated; and (2) chemotherapy-naïve patients, where paclitaxel dose was escalated and carboplatin AUC was fixed at 6 mg.min/mL. PK studies of paclitaxel and carboplatin were performed on day 1 of course 1. RESULTS: Fifty-eight patients were treated with 186 courses of paclitaxel, carboplatin, and valspodar. Neutropenia, thrombocytopenia, and hepatic transaminase elevations were DLTs. In previously treated patients, no DLTs occurred at the first dose level (paclitaxel 54 mg/m(2) and carboplatin AUC 6 mg.min/mL). However, one of 12, two of six, two of four, four of 11, and two of five patients experienced DLTs at doses of paclitaxel (mg/m(2))/carboplatin AUC (mg.min/mL) of 67.5/6, 81/6, 94.5/6, 67. 5/7.5, and 67.5/9, respectively. In chemotherapy-naïve patients, one of 17 developed DLT at paclitaxel 81 mg/m(2) and carboplatin AUC 6 mg/mL.min. There was prolongation of the terminal phase of paclitaxel elimination as evidenced by an increased time that plasma paclitaxel concentration was >/= 0.05 micromol/L, ranging from 16.6 +/- 6.7 hours to 41.5 +/- 9.8 hours for paclitaxel doses of 54.5 mg/m(2) to 94.5 mg/m(2), respectively. CONCLUSION: The recommended phase II dose in chemotherapy-naïve patients is paclitaxel 81 mg/m(2), carboplatin AUC 6 mg.min/mL, and valspodar 5 mg/kg every 6 hours. In previously treated patients, the recommended phase II dose is paclitaxel 67.5 mg/m(2), carboplatin AUC 6 mg.min/mL, and valspodar 5 mg/kg every 6 hours. The acceptable toxicity profile supports the rationale for performing disease-directed evaluations of paclitaxel, carboplatin and valspodar on the schedule evaluated in this study.

Phase I study of paclitaxel in combination with a multidrug resistance modulator, PSC 833 (Valspodar), in refractory malignancies.

PURPOSE: To determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of paclitaxel when given with PSC 833 (valspodar) to patients with refractory solid tumors. PATIENTS AND METHODS: Patients were initially treated with paclitaxel 175 mg/m(2) continuous intravenous infusion (CIVI) over 3 hours. Subsequently, 29 hours of treatment with CIVI PSC 833 was started 2 hours before paclitaxel treatment was initiated. In this combination, the starting dose of paclitaxel was 52.5 mg/m(2). Paclitaxel doses were escalated by 17.5 mg/m(2) increments for four subsequent cohorts. Each cohort consisted of three patients with the exception of the last cohort, which consisted of six patients. Data for the pharmacokinetics of paclitaxel with and without concurrent PSC 833 administration were obtained. RESULTS: All 18 patients completed at least one course of concurrent treatment (median, two courses; range, one to six) and were evaluable for toxicity. The MTD for paclitaxel with PSC 833 was 122.5 mg/m(2). Neutropenia was the DLT. All patients had PSC 833 blood concentrations greater than 1, 000 ng/mL before, during, and 24 hours after the paclitaxel infusion. PSC 833 produced small increases in the paclitaxel peak plasma concentrations and areas under the concentration-time curve. However, PSC 833 greatly prolonged the terminal phase of paclitaxel, resulting in plasma paclitaxel concentrations of more than 0.05 micromol/L for much longer than expected. As a result, myelosuppression was comparable to that produced by full-dose paclitaxel given without PSC 833. Of the 16 patients who were assessable for response, one patient experienced a partial response and an additional nine patients experienced disease stabilization after paclitaxel treatment alone. CONCLUSION: Treatment with paclitaxel 122.5 mg/m(2) as a 3-hour CIVI concurrent with a 29-hour CIVI of PSC 833 results in acceptable toxicity. The addition of PSC 833 alters the pharmacokinetics of paclitaxel, which explains the enhanced neutropenia experienced by patients treated with this drug combination.

Phase I trial of paclitaxel and etoposide for recurrent ovarian carcinoma: a Gynecologic Oncology Group Study.

A phase I study was performed to determine the maximum tolerated doses of intravenous etoposide and paclitaxel for women with previously treated persistent or recurrent ovarian cancer. Starting doses were paclitaxel 135 mg/m2 during 24 hours and etoposide 50 mg/m2/day for 3 consecutive days. The study was designed to escalate first the dose of etoposide, and then the dose of paclitaxel, in successive cohorts of patients. In an attempt to determine whether toxicity was affected by sequence of the drugs, the order of administration of the two drugs was reversed on alternate cycles. The starting doses of paclitaxel (135 mg/m2/24 hours) and etoposide (50 mg/m2/day x 3) caused severe neutropenia even with the addition of granulocyte colony-stimulating factor, and the trial was amended to administer the paclitaxel during 3 hours. However, this also proved too myelosuppressive without growth factor support. Twenty-one women were treated. A complete response was observed in one of nine patients with measurable disease, and a major decrease in CA-125 was noted in two patients who did not have measurable disease. Because of the severe myelosuppression observed in most patients, dose reduction was often required after the first cycle. The power to detect sequence-dependent variation in toxicity was minimal; however, no large differences were observed. A combination of the usual doses of these drugs will be difficult to administer in patients who have received previous chemotherapy for ovarian cancer.

Modulation of the multidrug resistance P-glycoprotein: detection with technetium-99m-sestamibi in vivo.

UNLABELLED: Overexpression of the multidrug resistance (MDR1) P-glycoprotein (Pgp) has been documented in nearly all forms of human cancers and increased levels of Pgp in some tumors correlate with poor response to treatment. Technetium-99m-sestamibi has recently been validated as a Pgp transport substrate. Pgp is also normally expressed along the biliary canalicular surface of hepatocytes and the luminal side of proximal tubule cells in the kidney, while not expressed in heart. METHODS: Focused on these organs with known Pgp status, we present the findings on 99mTc-sestamibi scintigraphy of three patients with refractory cancer who were imaged before and after administration of SDZ PSC 833, a second-generation, high-potency modulator of Pgp. RESULTS: Before treatment with SDZ PSC 833, scintigraphy using 99mTc-sestamibi showed normal, prompt clearance of the radiotracer from the liver and kidneys relative to the heart. After administration of the Pgp modulator, 99mTc-sestamibi was selectively retained in the liver and kidneys. CONCLUSION: Hepatobiliary and renal clearance of 99mTc-sestamibi are Pgp-mediated, and inhibition of Pgp transport in these organs can be successfully imaged using 99mTc-sestamibi in patients. Similar results might be expected with this and related radiopharmaceuticals for functional imaging of Pgp transport and modulation in tumors.

HPLC method for monitoring SDZ PSC 833 in whole blood.

P-glycoprotein (Pgp) is a 170-kDa membrane transporter that mediates drug efflux and is an effector of multidrug resistance. SDZ PSC 833 (PSC), a nonimmunosuppressive cyclosporine that potently modulates Pgp, is currently under clinical evaluation in patients with cancer. We have developed a reversed-phase HPLC assay for determining PSC blood concentrations that utilizes a step gradient with linear segments to resolve PSC into two distinct peaks (likely to be keto and enol isomers). To clinically validate the assay, PSC concentrations were obtained by HPLC from nine patients receiving oral doses of 5 mg/kg every 6 h. Values ranged from 0.91 to 5.4 mg/L during the dosing period, comparable with concentrations of PSC that modulate Pgp in vitro. In addition, we investigated the immunoreactivity of the Abbott TDx cyclosporin A (CsA) monoclonal whole-blood assay for PSC. The TDx CsA assay cross-reacts approximately 17% with PSC as determined by adding known amounts of PSC to whole blood. When PSC concentrations obtained by the TDx CsA assay were divided by 0.17, we found agreement between the TDx CsA assay and the HPLC PSC assay for samples from nine patients.

Differential changes in genome structure and expression of the mdr gene family in multidrug-resistant murine erythroleukemia cell lines.

The genome structure and expression of mdr genes were examined in multidrug-resistant sublines of two different murine (DBA/2J) Friend erythroleukemia cell lines, PC4 and C7D, derived by stepwise exposure to increasing concentrations of adriamycin beginning with 5 ng/ml. The PC4 cell lines selected in higher drug concentrations (80-1280 ng/ml) demonstrated amplification of all three mdr genes with preferential amplification of mdr3. Overexpression of the mdr2 and mdr3 genes accompanied their genomic amplification; however, expression of mdr1 was not seen despite amplification. In the C7D cell lines selected with higher drug concentrations (40-160 ng/ ml), amplification and overexpression of mdr1 and mdr2 without mdr3 was observed. Increased expression of mdr1 occurred prior to gene amplification. The distribution of mdr-specific genes in micrococcal nuclease-generated chromatin fractions differing in transcriptionally active sequences and proteins was different between the parent and drug-resistant sublines. An enrichment (two- to threefold) of mdr3 genes in the H1-depleted mononucleosome fraction enriched for actively transcribed genes (e.g., globin) was detected by Southern analysis of chromatin fractions in PC4-80 cells (selected in 80 ng/ml of adriamycin and overexpressing mdr3), compared to the parental cells. mdr3 enrichment was also detected using a new PCR-based method, which examined mdr3 genes and repetitive sequences. Of note, the H1-depleted chromatin fraction from PC4-20 showed enrichment of the mdr3 gene, although mdr3 expression was not detected in the cell line. These studies showed a different pattern of gene amplification and overexpression in genetically related erythroleukemia cell lines selected for resistance to the same chemotherapeutic agent. A change in chromatin organization of mdr genes preceded overexpression and amplification of the mdr3 gene.

Overexpression of the multidrug resistance-associated protein (MRP) gene in vincristine but not doxorubicin-selected multidrug-resistant murine erythroleukemia cells.

Multidrug-resistant sublines of the murine erythroleukemia cell line PC4 were sequentially selected in increasing vincristine concentrations (5-160 ng/ml). The low- and intermediate-level resistant cell lines, selected in < or = 40 ng/ml of vincristine, demonstrated resistance to Vinca alkaloids and to an epipodophyllotoxin but little or none to an anthracycline. The expression of murine mdr genes, as analyzed by Northern blotting, revealed a baseline expression of murine mdr2 in parental cells that was unchanged in the drug-resistant cell lines. Overexpression of mdr3 was observed only in the highest-level resistant cell line, PC-V160, whereas mdr1 mRNA was not detected in any of the cell lines. The polymerase chain reaction, using mdr3-specific primers, excluded the possibility that low levels of P-glycoprotein expression contributed to the resistance phenotype in the low and intermediate-level resistant cell lines. Northern blot analysis using a human complementary DNA probe for the multidrug resistance-associated protein (MRP) demonstrated overexpression of murine mrp in each of the vincristine-selected sublines. Genomic amplification of the mrp gene was coincident with mrp overexpression. The expression of mrp was also examined in two series of previously characterized doxorubicin-selected cell lines derived from parental PC4 and C7D murine erythroleukemia cells. In contrast to the vincristine-selected cell lines, overexpression of mrp was not detected. These studies demonstrate that, in murine erythroleukemia cells selected for vincristine resistance, overexpression of murine mrp occurred prior to that for murine mdr. In contrast to human MRP, selection for vincristine, but not doxorubicin resistance, resulted in the overexpression of murine mrp.

Management of locally advanced carcinoma of the breast. II. Inflammatory carcinoma.

BACKGROUND: Inflammatory carcinoma of the breast has been associated with a poor prognosis. Several therapeutic approaches have been under investigation in an effort to improve outcome. METHODS: This is a retrospective analysis of 179 patients with histologically confirmed inflammatory carcinoma of the breast: 33 treated with irradiation alone, 35 with combined irradiation and chemotherapy, 25 with irradiation and surgery, and 86 with a combination of three modalities. RESULTS: The 5-year disease free survival (DFS) rates were 40% for patients treated with three modalities, 24% for those treated with irradiation and surgery, and 6% for those treated with irradiation alone or in combination with chemotherapy without a surgical procedure. The 10-year DFS rates were 35%, 24%, and 0%, respectively. Cause specific survival (CSS) curves closely follow the same trends. A clearly superior locoregional tumor control was observed in patients who underwent a surgical procedure: 79% with three modalities, 76% with irradiation and surgery, and only 30% with irradiation alone or in combination with chemotherapy. Distant metastasis occurred in 57% of the group treated with triple-modality therapy, 60% of those treated with irradiation plus surgery, and 85% of the patients treated with irradiation alone or in combination with chemotherapy. There was no significant correlation between the type of mastectomy or doses of irradiation and locoregional tumor control or survival. The significant morbidity of the trimodal therapy (10%), although somewhat higher than that of other modalities (3.2%), was acceptable. CONCLUSIONS: The addition of mastectomy to irradiation significantly improved locoregional tumor control, DFS, and CSS; differences were statistically significant. The combination of chemotherapy, surgery, and irradiation had a significant impact on locoregional tumor control and incidence of distant metastases compared with surgery plus irradiation, and a lesser impact, although still statistically significant, on DFS and CSS. Further clinical trials are needed to optimize the management of patients with inflammatory breast cancer.

Cytotoxicity and DNA lesions produced by mitomycin C and porfiromycin in hypoxic and aerobic EMT6 and Chinese hamster ovary cells.

Solid neoplasms may contain deficient or poorly functional vascular beds, a property that leads to the formation of hypoxic tumor cells, which form a therapeutically resistant cell population within the tumor that is difficult to eradicate by ionizing irradiation and most existing chemotherapeutic agents. As an approach to the therapeutic attack of hypoxic cells, we have measured the cytotoxicity and DNA lesions produced by the bioreductive alkylating agents mitomycin C and porfiromycin, two structurally similar antibiotics, in oxygen-deficient and aerobic cells. Mitomycin C and porfiromycin were preferentially cytotoxic to hypoxic EMT6 cells in culture, with porfiromycin producing a greater differential kill of hypoxic EMT6 cells relative to their oxygenated counterparts than did mitomycin C. Chinese hamster ovary cells were more resistant to these quinone antibiotics; although in this cell line, porfiromycin was significantly more cytotoxic to hypoxic cells than to aerobic cells, and the degree of oxygenation did not affect the toxicity of mitomycin C. Alkaline elution methodology was utilized to study the formation of DNA single-strand breaks and DNA interstrand cross-links produced by mitomycin C and porfiromycin in both EMT6 and Chinese hamster ovary cells. A negligible quantity of DNA single-strand breaks and DNA interstrand cross-links were produced in hypoxic and aerobic Chinese hamster ovary cells by exposure to mitomycin C or porfiromycin, a finding consistent with the considerably lower sensitivity of this cell line to these agents. In EMT6 tumor cells, no single-strand breaks appeared to be produced by these antitumor antibiotics under both hypoxic and aerobic conditions; however, a significant number of DNA interstrand cross-links were formed in this cell line following drug treatment, with substantially more DNA interstrand cross-linking being produced under hypoxic conditions. Mitomycin C and porfiromycin caused the same amount of cross-linking under conditions of oxygen deficiency; however, mitomycin C produced considerably more DNA cross-linking than did porfiromycin in oxygenated cells. DNA interstrand cross-links were observed in hypoxic EMT6 cells throughout a 24-h period following removal of mitomycin C and porfiromycin, with a decrease in DNA interstrand cross-links observed at 24 h. An increase in DNA interstrand cross-links occurred in aerobic EMT6 cells treated with mitomycin C and porfiromycin at 6 h after drug removal, with a decrease in these lesions being observed by 24 h, suggesting that the rate of formation of the cross-links may be slower and the removal of cross-links more rapid under aerobic conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemotherapeutic attack of hypoxic tumor cells by the bioreductive alkylating agent mitomycin C.

Since the cure of solid tumors is limited by the presence of cells with low oxygen contents, we have approached the development of treatment regimens and of new drugs for these tumors by investigating agents which are preferentially bioactivated under hypoxia. Major emphasis has been directed at studying the mode of action of the mitomycin antibiotics, as bioreductive alkylating agents. Using primarily the EMT6 mouse mammary carcinoma as a solid tumor model, we have found that mitomycin C and porfiromycin are preferentially toxic to cells with low oxygen contents. The mitomycin analog BMY-25282 is more toxic to hypoxic cells than are mitomycin C and porfiromycin; however, unlike these antibiotics, BMY-25282 is preferentially toxic to well-oxygenated cells. With these three mitomycins, we have observed a correlation between cytotoxicity to hypoxic cells, the rate of generation of reactive products, and the redox potentials of the drugs. Investigations of the enzymes in EMT6 cells that could possibly activate mitomycin C have revealed that cytochrome P-450 and xanthine oxidase are not present in measurable quantities and therefore are not responsible for activation of mitomycin C. Activities representative of NADPH-cytochrome c reductase and DT-diaphorase are present in these neoplastic cells. Comparison of these enzymatic activities in EMT6, CHO, and V79 cells with the rate of generation of reactive products under hypoxia shows a direct correlation between these two parameters, but there is no quantitative correlation between these two parameters and the amount of cytotoxicity. Use of purified NADPH-cytochrome c reductase and inhibitors of this enzyme demonstrated that NADPH-cytochrome c reductase can activate mitomycin C, but that it is probably not the only enzyme participating in this bioactivation in EMT6 cells. The DT-diaphorase inhibitor dicoumarol was employed to show that this enzyme is not involved in the activation of mitomycin C to a cytotoxic agent. Instead, DT-diaphorase appears to metabolize mitomycin C to a nontoxic product. This property has been exploited to develop a new treatment regimen for solid tumors. Using X-rays to eliminate well oxygenated cells of a solid tumor implant of the EMT6 carcinoma, we have found that the combination of dicoumarol plus mitomycin C is more toxic to hypoxic tumor cells in vivo than mitomycin C alone. Furthermore, knowledge of the biochemical mechanism of mitomycin C activation permits a prediction of which tumors can best be treated with this combination of drugs by measuring enzymatic activities in biopsy specimens.

Role of NADPH:cytochrome c reductase and DT-diaphorase in the biotransformation of mitomycin C1.

Hypoxic cells of solid tumors are difficult to eradicate by X-irradiation or chemotherapy; as an approach to this problem, our laboratories are investigating the effects of the bioreductive alkylating agent mitomycin C (MC) on hypoxic cells. This antibiotic was preferentially toxic to EMT6 mouse mammary tumor cells and V79 Chinese hamster lung fibroblasts under hypoxic conditions, but it was equitoxic to Chinese hamster ovary cells in the presence and absence of oxygen. All cell lines catalyzed the formation of reactive metabolites under hypoxic conditions and contained NADPH:cytochrome c reductase and DT-diaphorase, two enzymes which may be responsible for the cellular activation of MC. Although a correlation existed between enzymatic activities and the formation of reactive metabolites from MC, there was no correspondence between these parameters and the degree of cytotoxicity expressed by MC under hypoxic conditions. Purified NADPH:cytochrome c reductase reduced MC in the absence of oxygen, with addition of cytochrome P-450 enhancing, but not participating directly in, the reduction reaction. Addition of NADP+ to cell sonicates substantially reduced NADPH:cytochrome c reductase activity, while the formation of reactive metabolites was affected only slightly; converse results were observed using mersalyl. Exposure of cell sonicates to dicumarol inhibited DT-diaphorase activity, while the rate of formation of reactive metabolites of MC was enhanced. The findings suggest that NADPH:cytochrome c reductase and some as yet to be identified enzyme(s) are important for the reductive activation of MC. DT-diaphorase and cytochrome P-450 are not directly involved in the activation of MC, but they appear to modulate the degree of activation to reactive species, which are presumably responsible for the observed cytotoxicity.