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Previous studies using the mutant Chinese hamster ovary cell line VpmR-5 indicate that its resistance to epipodophyllotoxins and intercalating agents is likely to be mediated through a qualitative change in type II topoisomerase that confers resistance to drug-stimulated DNA cleavage activity. In a further investigation of the genetic basis of drug resistance in VpmR-5 cells, we fused a hypoxanthine-guanine phosphoribosyl transferase-deficient subline of VpmR-5 (Vtgm-6) with normal human lymphocytes and analyzed the resultant hybrid lines (HL) for altered drug sensitivity. In all, 3 of 16 hybrid clones exhibited partial reconstitution of sensitivity to etoposide, mitoxantrone, doxorubicin, and 5-iminodaunorubicin while retaining complete resistance to m-AMSA. However, enhanced sensitivity to drug-induced DNA cleavage activity was observed only for etoposide. Biochemical and molecular-marker analysis of the hybrids failed to identify human chromosome 17 (the provisional location of TOP2) or any other human chromosome that is consistently and uniquely associated with drug sensitivity. We therefore sought to verify the chromosomal assignment of TOP2 by Southern blot hybridization of TOP2 cDNA on a human hybrid mapping panel and confirmed its location on chromosome 17. However, no hybridizing sequence to the TOP2 cDNA was found in any of the 16 Vtgm-6 hybrid lines. Efforts to select more directly for human chromosome 17 VpmR-5 hybrids using microcell fusion of mouse A9 cells carrying human 17 linked to pSV2neo were unsuccessful. None of the five hybrid clones thus obtained had 17q markers, including the gene for TOP2. Although the mechanism underlying partial reversion to a drug-sensitive phenotype in the original Vtgm-6 hybrid lines has yet to be defined, the data obtained in these lines indicate that anthracycline- and anthracenedione-induced cytotoxic effects can be dissociated from DNA cleavage activity. This suggests that pathways distal to cleavable-complex formation or, alternatively, independent of interactions with topoisomerase II that involve other intracellular targets are important in mediating the cytotoxicity produced by these drugs. [ABSTRACT FROM AUTHOR]

The nuclear enzyme, topoisomerase II, is the major site of action for cancer chemotherapy agents such as etoposide, teniposide, and a variety of intercalating agents. These compounds cause the enzyme to cleave DNA, forming a DNA-protein complex that may be a key step leading to cell death. It is apparently unique as a chemotherapy target, since drug potency diminishes with decreasing enzyme activity. It was thus of interest to examine the topoisomerase content and drug-induced DNA cleavage in freshly obtained human leukemia cells and to compare the obtained data with the results of similar studies performed in well-characterized human leukemia cell lines. The human T-lymphoblast line, CCRF-CEM, was more than 100-fold more sensitive to the DNA-cleavage effect of etoposide than the cells of the 13 leukemic patients examined. One of the leukemia lines (HL-60) and a lymphoblastoid line (RPMI-7666) were somewhat less sensitive than cells of the CCRF-CEM cells, but were still 10-fold more sensitive than the patients studied. The relative insensitivity of the freshly obtained cells could not be accounted for by differences with respect to drug uptake but were associated with markedly reduced topoisomerase-II content as assayed by immunoblotting using a mouse polyclonal serum against topoisomerase II. Heterogeneity was observed in the sensitivities of patients' cells with respect to both drug-induced DNA cleavage and enzyme content. The observed differences between cultured cell lines and patients' cells may have been related to their proliferative status. Etoposide potency in normal resting lymphocytes resembles that observed in circulating leukemia cells. However, following mitogenesis with phytohemagglutinin and interleukin-2, proliferating lymphocytes become as sensitive to etoposide as cultured cell lines with regard to DNA cleavage. This effect was accompanied by an increase in topoisomerase-II content. Our data thus support the hypothesis that topoisomerase-II content may be an important determinant of cell sensitivity to certain classes of chemotherapy agents. Efforts to stimulate topoisomerase-II content may improve the therapeutic efficacy of these drugs. [ABSTRACT FROM AUTHOR]

Editorial. Focuses on the association of tobacco exposure with small-cell lung cancer (SCLC). Treatment of SCLC; Prospects for SCLC patient survival; Evidence supporting the association of lung cancer with tobacco exposure.

Background The survival advantage of induction chemotherapy (IC) followed by locoregional treatment is controversial in locally advanced head and neck squamous cell carcinoma (LAHNSCC). We previously showed feasibility and safety of cetuximab-based IC (paclitaxel/carboplatin/cetuximab—PCC, and docetaxel/cisplatin/5-fluorouracil/cetuximab—C-TPF) followed by local therapy in LAHNSCC. The primary end point of this phase II clinical trial with randomization to PCC and C-TPF followed by combined local therapy in patients with LAHNSCC stratified by human papillomavirus (HPV) status and T-stage was 2-year progression-free survival (PFS) compared with historical control. Patients and methods Eligible patients were ≥18 years with squamous cell carcinoma of the oropharynx, oral cavity, nasopharynx, hypopharynx, or larynx with measurable stage IV (T0–4N2b–2c/3M0) and known HPV by p16 status. Stratification was by HPV and T-stage into one of the two risk groups: (i) low-risk: HPV-positive and T0–3 or HPV-negative and T0–2; (ii) intermediate/high-risk: HPV-positive and T4 or HPV-negative and T3–4. Patient reported outcomes were carried out. Results A total of 136 patients were randomized in the study, 68 to each arm. With a median follow up of 3.2 years, the 2-year PFS in the PCC arm was 89% in the overall, 96% in the low-risk and 67% in the intermediate/high-risk groups; in the C-TPF arm 2-year PFS was 88% in the overall, 88% in the low-risk and 89% in the intermediate/high-risk groups. Conclusion The observed 2-year PFS of PCC in the low-risk group and of C-TPF in the intermediate/high-risk group showed a 20% improvement compared with the historical control derived from RTOG-0129, therefore reaching the primary end point of the trial. [ABSTRACT FROM AUTHOR]

Cisplatin-based chemotherapy improves survival in appropriately selected patients with stage IV non-small cell lung cancer (NSCLC). However, cisplatin-based regimens have well-known dose-related toxicities, particularly renal insufficiency and neurotoxicity. On the basis of prior preclinical and phase I studies, we initiated a phase II study of SPI-77 (STEALTH) Liposomal Cisplatin) in patients with stage IIIB and IV NSCLC who failed previous treatment with platinum. Disease in all subjects had progressed during therapy, failed to respond, or progressed within 3 months after discontinuing the platinum-based chemotherapy. Between January and June 1999, 13 patients were enrolled at our institution. Patient characteristics included: seven women, six men; median age, 61 years; median Karnofsky performance status, 80%; median number of prior chemotherapy regimens, two (range, 1-3). All patients had adequate hepatic and renal function. SPI-77 was administered at a dose of 260 mg/m(2) IV every 3 weeks. A median of two cycles (range 1-6) were given; the total number of cycles was 35. Among the 12 patients evaluable for response, two had (17%) stable disease and ten (83%) had progressive disease. The median survival was 24.3 weeks, and the median follow-up was 43.9 weeks. Toxicity could be evaluated in all subjects. Moderate anemia (46% of cycles, or=grade 3) with minimal granulocytopenia and thrombocytopenia (26% of cycles grade 1; 0% of cycles, >or=grade 2) were the most notable manifestations of myelosuppression. Grade 3 nonhematological toxicities included dyspnea (8%), fatigue (8%), and pain (8%). There were no grade 4 toxicities. These data suggest that this liposomal cisplatin formulation does not have appreciable activity in this population of patients with NSCLC who had received prior platinum-based chemotherapy. The lack of encouraging results from SPI-77 use in other phase I and II studies resulted in early closure of this trial by the manufacturer.

The epidermal growth factor receptor (EGFR) signaling pathway plays an important role in a number of processes that are key to tumor progression, including cell proliferation, angiogenesis, metastatic spread, and inhibition of apoptosis. EGFR is expressed or overexpressed in non-small-cell lung cancer (NSCLC), and EGFR-mediated growth has been associated with advanced disease and poor prognosis in NSCLC patients. ZD1839 (Iressa) is an orally active, selective EGFR-tyrosine kinase inhibitor that blocks EGFR signal transduction. In preclinical studies using NSCLC cell lines, ZD1839 has been shown to inhibit tumor cell growth. In addition, ZD1839, as monotherapy and in combination with commonly used cytotoxic agents, has produced growth delay in NSCLC human xenografts. Preliminary results from phase I trials in patients with advanced disease have shown that ZD1839 has excellent bioavailability, an acceptable tolerability profile, and promising clinical activity in patients with a variety of tumor types, particularly in NSCLC. ZD1839 is currently in phase III clinical development for the treatment of advanced NSCLC.

Purpose: Retinoids and interferons (IFNs) have single-agent and synergistic combined effects in modulating cell proliferation, differentiation, and apoptosis in vitro and clinical activity in vivo in the head and neck and other sites. Alpha-tocopherol has chemopreventive activity in the head and neck and may decrease 13-cis-retinoic acid (13-cRA) toxicity. We designed the present phase II adjuvant trial to prevent recurrence or second primary tumors (SPTs) using 13-cRA, IFN-alpha, and alpha-tocopherol in locally advanced-stage head and neck cancer., Patients and Methods: After definitive local treatment with surgery, radiotherapy, or both, patients with locally advanced SCCHN were treated with 13-cRA (50 mg/m(2)/d, orally, daily), IFN-alpha (3 x 10(6) IU/m(2), subcutaneous injection, three times a week), and alpha-tocopherol (1,200 IU/d, orally, daily) for 12 months, with a dose modification. Screening for recurrence or SPTs was performed every 3 months., Results: Tumors of 11 (24%) of the 45 treated patients were stage III, and 34 (76%) were stage IV. Thirty-eight (86%) of 44 patients completed the full 12-month treatment (doses modified as needed). Toxicity generally was consistent with previous IFN and 13-cRA reports and included mild to moderate mucocutaneous and flu-like symptoms; occasional significant fatigue (grade 3 in 7% of patients), mild to moderate hypertriglyceridemia in 30% of patients who continued treatment along with antilipid therapy, and mild hematologic side effects. Six patients did not complete the planned treatment because of intolerable toxicity or social problems. At a median 24-months of follow-up, our clinical end point rates were 9% for local/regional recurrence (four patients), 5% for local/regional recurrence and distant metastases (two patients), and 2% for SPT (one patient), which was acute promyelocytic leukemia (ie, not of the upper aerodigestive tract). Median 1- and 2-year rates of overall survival were 98% and 91%, respectively, and of disease-free survival were 91% and 84%, respectively., Conclusion: The novel biologic agent combination of IFN-alpha, 13-cRA, and alpha-tocopherol was generally well tolerated and promising as adjuvant therapy for locally advanced squamous cell carcinoma of the head and neck. We are currently conducting a phase III randomized study of this combination (v no treatment) to confirm these phase II study results.

C225, a human-mouse chimerized monoclonal antibody directed against the epidermal growth factor receptor (EGFr), has a synergistic effect with cisplatin in xenograft models. To determine the tumor EGFr saturation dose with C225 and the fate of infused C225, we conducted a Phase Ib study with C225 in combination with cisplatin in patients with recurrent squamous cell carcinoma of the head and neck. Using tumor samples, we assessed tumor EGFr saturation by antibody using immunohistochemistry studies, the EGFr tyrosine kinase assay, and detection of the EGFr/C225 complex formation by immunoblot. Potential candidates were screened for EGFr expression in their tumors, and 12 patients who had high levels of EGFr expression and tumors easily accessible for repeated biopsies (pretherapy, 24 h after first C225 infusion, 24 h before third C225 infusion) were entered at three different dose levels of C225 with a fixed dose of cisplatin. The median value of tumor EGFr saturation increased to 95% at the higher dose levels. EGFr tyrosine kinase activity was significantly reduced after C225 infusion, and EGFr/C225 complexes were also detected at higher doses of C225. The loading dose of C225 at 400 mg/m(2) with a maintenance dose at 250 mg/m(2) achieved a high percentage of saturation of EGFr in tumor tissue, and these doses were recommended for Phases II or III clinical trials. Six (67%) of nine evaluable patients achieved major responses, including two (22%) complete responses. Mild to moderate degrees of allergic reaction and folliculitis-like skin reactions were demonstrated. We conclude that infused C225 binds and significantly saturates tumor EGFr, which may render a high degree of antitumor activity, and provides a novel mechanism for targeting cancer therapy for patients who have EGFr expression in their tumors.

Purpose: This trial was designed to determine the maximum-tolerated dose, toxicity, and pharmacology of oral green tea extract (GTE) once daily or three times daily., Patients and Methods: Cohorts of three or more adult cancer patients were administered oral GTE with water after meals one or three times daily for 4 weeks, to a maximum of 6 months, depending on disease response and patient tolerance. Pharmacokinetic analyses were encouraged but optional., Results: Dose levels of 0.5 to 5.05 g/m(2) qd and 1.0 to 2.2 g/m(2) tid were explored. A total of 49 patients were studied., Patient Characteristics: median age, 57 years (range, 27 to 77 years); 23 patients were women (47%); 98% had a Zubrod PS of 1%; 98% had PS of 1; and 21 had non-small-cell lung, 19 had head & neck cancer, three had mesothelioma, and six had other. Mild to moderate toxicities were seen at most dose levels and promptly reversed on discontinuation of GTE. Dose-limiting toxicities were caffeine related and included neurologic and gastrointestinal effects. The maximum-tolerated dose was 4.2 g/m(2) once daily or 1.0 g/m(2) three times daily. No major responses occurred; 10 patients with stable disease completed 6 months of GTE. Pharmacokinetic analyses found accumulation of caffeine levels that were dose dependent, whereas epigallocatechin gallate levels did not accumulate nor appear dose related., Conclusion: A dose of 1.0 g/m(2) tid (equivalent to 7 to 8 Japanese cups [120 mL] of green tea three times daily) is recommended for future studies. The side effects of this preparation of GTE were caffeine related. Oral GTE at the doses studied can be taken safely for at least 6 months.

Twenty-four patients with pleural mesothelioma received 50 mg/m2 of Doxil every four weeks. At follow-up, the disease had stabilized in 43% percent of patients and had progressed in 57%. No objective responses were observed. Estimated median survival of all patients was 37 weeks. Major toxicities were erythrodysesthesia of hands and feet and myelosuppression. No cardiac toxicity was observed. We concluded that Doxil at this dosage and schedule is inactive against pleural mesothelioma.

Patients with advanced squamous cell head and neck cancer have a dismal long-term survival rate not only because of metastatic disease, but also primarily because of failure in local disease control. The role of chemotherapy in recurrent or metastatic head and neck cancer has largely been palliative. Several chemotherapy agents, including docetaxel, paclitaxel, and ifosfamide, have been extensively studied, either alone or in combination regimens, for the treatment of recurrent or metastatic disease. These have resulted in response rates that are similar or higher than those obtained with the gold standard combination, cisplatin/ fluorouracil. Single-agent and combination studies of vinorelbine and gemcitabine have demonstrated modest activity in recurrent or metastatic disease. Phase III trials are planned that will compare taxane-based regimens with cisplatin and 5-fluorouracil in recurrent or metastatic head and neck cancer. Meanwhile, new drug and compound development, including monoclonal antagonists to the epidermal growth factor receptor, farnesyl transferase inhibitors, and oncolytic viruses are being tested in this setting.

The immune responses of 10 patients with advanced non-small cell lung cancer receiving monthly intratumoral injections of a recombinant adenovirus containing human wild-type p53 (Ad-p53) to adenovirus and transgene antigens were studied. The predominate cellular and humoral immune responses as measured by lymphocyte proliferation and neutralizing antibody (Ab) formation were to adenovirus serotype 5 vector antigens, with increased responses in posttreatment samples. Consistent alterations in posttreatment cellular and humoral immune responses to p53 epitopes were not observed, and cytotoxic Abs to human lung cancer cells were not generated. Patients in this study had evidence of an antitumoral effect of this treatment with prolonged tumor stability or regression; however, neither Abs to p53 protein nor increased lymphocyte proliferative responses to wild-type or mutant p53 peptides have been consistently detected.

Purpose: Extrapolating from our experience delivering a "boost" field of radiation concurrently with fields treating both gross and subclinical disease at the end of a course of radiation therapy, we developed a regimen to deliver concurrent chemotherapy during the last 2 weeks of a conventionally fractionated course of radiation., Patients and Methods: Patients had stage III or IV biopsy-proven squamous cell carcinoma originating from a head and neck mucosal site. The regimen was 70 Gy delivered over 7 weeks with concurrent fluorouracil (5-FU) and cisplatin given daily with each radiation dose during the last 2 weeks. A phase I study was performed to determine the maximum-tolerated dose (MTD) before a phase II study was conducted., Results: The MTD was 400 mg/m(2) per day for 5-FU and 10 mg/m(2) per day for cisplatin. Mucositis persisting more than 6 weeks after therapy was the dose-limiting toxicity. A total of 60 patients were treated on the two phases of the study. Eighteen patients (35%) treated at the MTD developed prolonged mucositis. There were two cases of neutropenic sepsis, including one fatality. The actuarial 2-year rates for overall survival, freedom from relapse, and local control were 62%, 59%, and 80%, respectively., Conclusion: Preliminary locoregional control rates seem to be higher than those reported for treatment with radiation alone. Toxicity was also greater than that seen with radiation alone, but the regimen was designed to deliver an intense treatment schedule, which could be completed without significant interruptions, and to obtain high control rates above the clavicles. These end points were achieved.

Purpose: The combination of cisplatin, etoposide, and paclitaxel was studied in patients with extensive small-cell lung cancer in a phase I component followed by a phase II trial to determine the maximum-tolerated dose (MTD), characterize toxicity, and estimate response and median survival rates., Patients and Methods: Forty-one patients were treated between October 1993 and April 1997. Doses for the initial cohort were cisplatin 75 mg/m(2) on day 1, etoposide 80 mg/m(2)/d on days 1 to 3, and paclitaxel 130 mg/m(2) on day 1 over 3 hours. Cycles were repeated every 3 weeks for up to six cycles. The MTD was reached in the first six patients. In these six patients and in the next 35 patients, who were entered onto the phase II trial, response and survival were estimated., Results: At the initial dose level, one of six patients developed febrile neutropenia, and five of six achieved targeted neutropenia (nadir absolute granulocyte count, 100 to 1,000/microL) without any other dose-limiting toxicity, defining this level as the MTD. Grade 4 neutropenia was observed in 88 (47%) of 188 total courses administered at or less than the MTD. Neutropenia was associated with fever in only 17 (9%) of 188 courses, but two patients experienced neutropenic sepsis that was fatal. Nonhematologic toxicity greater than grade 2 was observed in 10 (5%) of 188 total courses, with fatigue, peripheral neuropathy, and nausea/vomiting most common. The overall objective response rate was 90% of 38 assessable patients: six complete responses (16%) and 28 partial responses(74%). Median progression-free and overall survival durations were 31 and 47 weeks, respectively., Conclusion: The combination of cisplatin, etoposide, and paclitaxel produced response and survival rates similar to those of other combinations and was well tolerated.

Background: Preclinical studies in animal models have demonstrated tumor regression following intratumoral administration of an adenovirus vector containing wild-type p53 complementary DNA (Ad-p53). Therefore, in a phase I clinical trial, we administered Ad-p53 to 28 patients with non-small-cell lung cancer (NSCLC) whose cancers had progressed on conventional treatments., Methods: Patients received up to six, monthly intratumoral injections of Ad-p53 by use of computed tomography-guided percutaneous fine-needle injection (23 patients) or bronchoscopy (five patients). The doses ranged from 10(6) plaque-forming units (PFU) to 10(11) PFU., Results: Polymerase chain reaction (PCR) analysis showed the presence of adenovirus vector DNA in 18 (86%) of 21 patients with evaluable posttreatment biopsy specimens; vector-specific p53 messenger RNA was detected by means of reverse transcription-PCR analysis in 12 (46%) of 26 patients. Apoptosis (programmed cell death) was demonstrated by increased terminal deoxynucleotide transferase-mediated biotin uridine triphosphate nick-end labeling (TUNEL) staining in posttreatment biopsy specimens from 11 patients. Vector-related toxicity was minimal (National Cancer Institute's Common Toxicity Criteria: grade 3 = one patient; grade 4 = no patients) in 84 courses of treatment, despite repeated injections (up to six) in 23 patients. Therapeutic activity in 25 evaluable patients included partial responses in two patients (8%) and disease stabilization (range, 2-14 months) in 16 patients (64%); the remaining seven patients (28%) exhibited disease progression., Conclusions: Repeated intratumoral injections of Ad-p53 appear to be well tolerated, result in transgene expression of wild-type p53, and seem to mediate antitumor activity in a subset of patients with advanced NSCLC.

Purpose: To improve the outcome of patients with locally advanced inoperable non-small cell lung cancer (NSCLC), we conducted a pilot trial of concurrent chemoradiation therapy using a cisplatin and oral etoposide regimen given concurrently with hyperfractionated radiation therapy., Methods and Materials: In this single-institution pilot trial, we enrolled 23 patients with inoperable Stage IIIa (4) and IIIb (19) NSCLC. Treatment consisted of two cycles of chemotherapy with oral etoposide 50 mg one day alternating with 50 mg b.i.d. (50 mg/day if BSA is < 1.70 m2) on days 1-21 and intravenous cisplatin (40 mg/m2) on days 1 and 8 of a 28-day cycle. Radiation therapy was given twice a day (1.2 Gy per fraction), 5 days a week, to a total dose of 69.6 Gy in 58 fractions over 6 weeks., Results: Overall, 18 (78%) of the 23 patients completed the chemotherapy as planned and 21 (91%) received thoracic irradiation per protocol. One patient died of radiation pneumonitis. Fourteen (78%) of 18 evaluable patients achieved objective responses. The median survival duration was 9.3 months for all patients and 20.2 months for 15 patients who had no more than 5% weight loss. After a minimum follow-up of 5 years, five patients (1 IIIa, 4 IIIb) are still alive and disease-free, which gives an actual 5-year survival rate of 22%. Four of the five 5-year survivors were among those who completed the treatment as planned., Conclusion: This long-term survival outcome compares favorably with that of other chemoradiation therapy trials and even with those reported in multimodality trials including surgery. These results suggest that intensive concurrent chemoradiation therapy is feasible, and some patients with locally advanced inoperable NSCLC may enjoy long-term survivorship following nonsurgical therapy.

The identification of genetic lesions that lead a normal cell to become malignant presents us with the opportunity of targeting those lesions as a means of therapy. Given the key role played by the tumor suppressor gene p53 in cell cycle regulation and apoptosis, and the evidence linking p53 mutations with non-small cell lung cancer, attempts at p53 replacement are a logical approach to therapy in this disease. In a phase I study, administration of an adenoviral p53 vector (Adp53) to 21 patients with advanced non-small cell lung cancer produced little toxicity. Up to six intratumoral injections at monthly intervals were well-tolerated. Expression of the p53 transgene was evident, along with potentially useful clinical responses. Time to disease progression in the indicator lesion treated with Adp53 appears to be enhanced by higher doses of vector, concomitant cisplatin therapy, and evidence of apoptosis on tumor biopsy specimens. Phase II trials should now be undertaken to determine the response rate to Adp53.

This phase I/II study investigated the efficacy and toxic effects of combination chemotherapy using paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), ifosfamide, and cisplatin (TIP) in patients with recurrent or metastatic squamous cell carcinoma of the head and neck. Twelve patients were entered in the phase I part of the study, results of which were reported previously. Fifty-three patients were treated in the phase II part of the study with 175 mg/m2 paclitaxel in a 3-hour infusion on day 1; 1,000 mg/m2/d ifosfamide in a 2-hour infusion on days 1 to 3; and 60 mg/m2 cisplatin on day 1, repeated every 3 to 4 weeks. Thirty-five men and 18 women were treated; the median age was 55 years (range, 27 to 73 years). Sites of disease and types of previous therapy varied among the patients. Among those with recurrent disease, 30 had locoregional disease, four had locoregional disease with distant metastasis, and 17 had distant metastasis only. Two patients had distant metastatic disease (MI) at the time of diagnosis. Of the 53 patients entered, 52 were assessable for disease response and toxic effects. Complete response was achieved in nine (17%) of 52 patients and partial response in 21 (40%); five (10%) patients had stable disease and 17 (33%) had progressive disease. When response rate was analyzed by disease sites, patients with locoregional sites showed a 43% major response (complete and partial) rate, and those with distant metastatic sites demonstrated an 80% major response rate (P=.04). The median duration of disease response in all patients was 4.9 months at completion of the study. Among the nine patients with complete response, three had progressive disease and the median duration of response was 6.9 months (range, 4.9 to 17 months); six were still in remission at the time of this writing, with a median duration of response of 12.8 months (range, 6.3 to 18.8+ months). The median survival time was 8.8 months, and the 1- and 2-year survival rates were 40% and 21.9%, respectively. The median follow-up time of the study was 11.8 months. The major toxic effects included neutropenia, cumulative peripheral neuropathy, and fatigue. Mucositis was rare; grade 3 mucositis developed in only one patient. Other side effects included neutropenic fever in 14 patients, all of whom completely recovered after antibiotic treatment. Grade 3 orthostatic hypotension and grade 3 peripheral neuropathy developed in one patient; supportive care led to gradual recovery. No deaths were caused by toxic effects. In conclusion, these preliminary results indicate that the TIP chemotherapy regimen produced high rates of major responses in patients with recurrent or metastatic head and neck squamous cell carcinoma, and responses were durable. The median, 1-year, and 2-year survival times were particularly promising. The TIP regimen should be pursued further as an induction regimen for locally advanced head and neck cancer.

Purpose: To assess the activity and toxicity profile of combined taxol (paclitaxel), ifosfamide, and platinum (cisplatin) (TIP) in patients with recurrent or metastatic squamous cell carcinoma (SCC) of the head and neck., Patients and Methods: Recurrent or metastatic head and neck SCC patients received paclitaxel 175 mg/m2 in a 3-hour infusion on day 1; ifosfamide 1,000 mg/m2 in a 2-hour infusion on days 1 through 3; mesna 600 mg/m2 on days 1 through 3; and cisplatin 60 mg/m2 on day 1, repeated every 3 to 4 weeks. All were premedicated with dexamethasone, diphenhydramine, and cimetidine. Prophylactic hematopoietic growth factors were not permitted., Results: Fifty-two patients were assessable for response and toxicity; 53 for survival (local-regional recurrence alone in 57% and distant metastasis with or without local-regional recurrence in 43%). Overall response rate was 58% (30 of 52) of patients; complete response rate was 17% (nine of 52) of patients, with six complete responses that continued for a median 15.7+ months. Median follow-up of all patients was 17.7 months. Median survival was 8.8 months (95% confidence interval [CI] 8.1 to 17.5 months). Toxicity was relatively well tolerated and caused no deaths. The most frequent moderate-to-severe toxicity (90% of patients) was transient grades 3 to 4 neutropenia; neutropenic fever occurred in 27%. Grade 3 peripheral neuropathy occurred in three patients, none had grade 4. Grade 3 mucositis occurred in only one patient, none had grade 4., Conclusion: TIP had major activity in this setting, with a 58% objective response rate, 17% complete response rate, durable complete responses (six of nine persisting), and relatively well-tolerated toxicity, with no toxic deaths. The activity of TIP, a novel taxol-cisplatin-based regimen, in recurrent or metastatic head and neck SCC should be confirmed in a phase III trial.

Previous data suggested interaction of cisplatin with interferon (IFN) in non-small cell lung cancer and a possible effect of IFN in maintaining remission in small cell lung cancer (SCLC). This study was designed to further examine the effect of IFN in the treatment of extensive disease (ED) SCLC. Forty previously untreated patients with performance status (PS) of 0-2 (Zubrod scale) were treated with etoposide (100 mg/m2 for 3 days), cisplatin (25 mg/m2 for 3 days) (EP), and recombinant IFN-alpha2a (rIFN-alpha2a) (5 x 10(6) U/m2 for 3 days) for six cycles (induction), followed by rIFN-alpha2a (5 x 10(6) U/m2) thrice weekly and megestrol acetate (40 mg q.i.d.) as maintenance therapy for 6 months or until progressive disease or intolerable toxicity was documented. Patients were 25 men (62%) and 15 women (38%), median age 58 (28-76), median Zubrod performance status 1 (0-2). Major sites of metastasis include liver (55%), bone (42%), bone marrow (25%), and adrenal gland (18%). Of 40 eligible patients accrued to this trial, 35 were evaluable for response, and 37 were evaluable for toxicity. There were 3 complete and 28 partial responses, for an overall response rate of 89%. With 39 of 40 patients followed until death, median survival (Kaplan-Meier) is estimated at 46 weeks (95% CI range 35-55). Twenty patients completed six cycles of induction, and 16 received maintenance therapy, median 2 cycles (range 1-3). Major toxicity during induction included grade 4 granulocytopenia in 24%, grade 2-3 nausea or vomiting or both in 41%, grade 2 fatigue in 24%, grade 2 anorexia in 22%, and grade 2-3 renal insufficiency in 9% of 175 total courses of chemotherapy administered. Toxicity during the maintenance phase was notable for grade 2-3 fatigue in 43%, grade 2-3 anorexia in 24%, grade 2-3 weight loss in 10%, and grade 3-4 anemia in 17% of 30 courses. There were no treatment-related deaths. The addition of rIFN-alpha2a to EP in induction chemotherapy of ED SCLC, followed by rIFN-alpha2a and megestrol acetate maintenance therapy, was reasonably well tolerated. The complete and overall response rates and duration of remission and survival appear to be similar to those generally obtained with EP alone in similar patients.

Current chemotherapeutic approaches to recurrent or metastatic head and neck cancer have yielded response rates of 10% to 20% for single agents and 30% to 40% for combination chemotherapy. Median survival for patients with recurrent or metastatic disease treated with single agents or combination chemotherapy is between 4 and 6 months. Investigation of new drugs, therefore, has high priority among clinicians and researchers. One new agent that has been effective as single-agent therapy is paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ). We tested the combination of paclitaxel, ifosfamide, and cisplatin in recurrent or metastatic head and neck cancer. The starting dose of paclitaxel was 175 mg/m2 as a 3-hour infusion on day 1, ifosfamide 1 g/m2 as a 2-hour infusion on days 1 to 3, and cisplatin 60 mg/m2 via 2-hour infusion on day 1. This schedule was repeated every 3 weeks. Sixty-five patients were entered into the study and 62 patients are currently evaluable for response and toxicity in the phase I and phase II portions of this study. We observed 10 (16%) complete responses and 24 (39%) partial responses. The overall response rate was 55% in phases I/II of this interim analysis. In the phase II part alone, we have observed eight (16%) complete responses and 22 (44%) partial responses to date among 50 evaluable patients. Median survival times were 8.9 months for all patients and 9.7 months for patients in the phase II part of the study. Preliminary results demonstrate significant antitumor activity in patients with recurrent or metastatic head and neck cancer. The paclitaxel/ifosfamide/cisplatin regimen was well tolerated. Chemotherapy with paclitaxel/ifosfamide/cisplatin should be tested as an induction regimen in patients with locally advanced head and neck cancer. It also warrants testing in a randomized setting to compare it with a standard regimen, such as the combination of 5-fluorouracil and cisplatin.

Chemotherapy has been rarely considered an important treatment modality for brain metastases. Based on the hypothesis that the lack of efficacy of chemotherapy, rather than the blood-brain barrier itself, may be the major hindrance to the successful chemotherapeutic treatment of brain metastases, we started a trial in which a selected group of non-small cell lung cancer patients with brain metastases received primary treatment with systemic chemotherapy. The treatment consisted of three courses of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) 225 mg/m2 given intravenously over 3 hours and carboplatin dosed to an area under the concentration-time curve of 6, with close monitoring of the lesion by computed tomography or magnetic resonance imaging of the brain after each chemotherapy course. Any radiographic or clinical evidence of progression in the brain during treatment or no improvement in the brain after three cycles of chemotherapy mandated whole brain irradiation (30 Gy in 10 fractions). Responding patients received three additional courses of chemotherapy; whole brain irradiation was given after completion of all six chemotherapy cycles. To date, five patients have been enrolled, and one has achieved partial remission both in the brain and at the extracranial site. Other patients did not achieve major objective responses either in the brain or at the extracranial sites. These preliminary results, which are consistent with the study hypothesis, support the feasibility of our approach. We therefore continue to accrue patients for this study.

Purpose: To assess the outcomes of patients with nasopharyngeal carcinoma (NPC) whose treatment was determined by computerized tomography (CT) and/or magnetic resonance imaging staging and to analyze the impact of induction chemotherapy and accelerated fractionated radiotherapy., Methods and Materials: The analysis is based on 122 of 143 previously untreated patients with NPC treated with radiation therapy at The University of Texas M. D. Anderson Cancer Center between 1983 and 1992. Excluded were 4 patients treated with palliative intent, 4 children, 12 patients not staged with CT, and 1 patient who died of a cerebrovascular accident prior to completion of treatment. The stage distribution was as follows: AJCC Stage I-2, Stage II-7, Stage III-12, Stage IV-101; Tl-15, T2-33, T3-22, T4-52; N0-32, N1-10, N2-47, N3-32, Nx-1. Fifty-nine (48%) patients had squamous cell carcinoma; 63 (52%) had lymphoepitheliomas, undifferentiated NPC or poorly differentiated carcinoma, NOS (UNPC). Sixty-seven patients (65 with Stage IV disease) received induction chemotherapy. Fifty-eight patients (24 of whom had induction chemotherapy) were treated with the concomitant boost fractionation schedule. The median follow-up for surviving patients was 57 months., Results: The overall actuarial 2- and 5-year survival rates were 78 and 68%, respectively. Forty-nine patients (40%) had disease recurrence. Thirty-three (27%) had local regional failures; 19 at the primary site only, 8 in the neck and 6 in both. Local failure occurred in 31% of patients staged T4 compared to 13% of T1-T3 (p = 0.007). Sixteen patients failed at distant sites alone. Among Stage IV patients the 5-year actuarial rates for patients who did and did not receive induction chemotherapy were as follows: overall survival: 68 vs. 56% (p = 0.02), freedom from relapse: 64 vs. 37% (p = 0.01), and local control: 86 vs. 56% (p = 0.009). The actuarial 5-year distant failure rate in patients with UNPC who were treated with induction chemotherapy and controlled in the primary and neck was 13%. In patients who did not receive chemotherapy, the actuarial 5-year local control rates for patients treated with concomitant boost or conventional fractionation were 66 and 67%, respectively., Conclusions: While not providing conclusive evidence, this single institution experience suggests that neoadjuvant chemotherapy for Stage IV NPC patients improves both survival and disease control. Recurrence within the irradiated volume was the most prevalent mode of failure and future studies will evaluate regimens to enhance local regional control.

Purpose: This study was designed to assess the anti-tumor activity of topotecan (TPT) in patients with small-cell lung cancer (SCLC) refractory to etoposide., Patients and Methods: Refractoriness to etoposide was defined as lack of response to etoposide-containing frontline therapy, or progression during or within 3 months of the last dose of etoposide-containing frontline or second-line therapy. Other eligibility criteria were presence of measurable disease, Zubrod scale performance status (PS) < or = 2, < or = two prior chemotherapy regimens, and adequate renal and liver function. TPT was administered at a dose of 1.25 mg/m2/d for 5 days over 30 minutes every 21 days., Results: Thirty-two patients were registered, of whom 28 are fully assessable. All patients had been treated with frontline etoposide and cisplatin. Three patients (11%) achieved a partial remission (PR) (durations, 7, 8, and 19 weeks) and two (7%) achieved a minor response; five patients (17%) had stable disease and 18 (65%) had progressive disease. One of the three patients who achieved a PR had failed to respond to frontline cisplatin and etoposide. The overall median survival duration was 20 weeks. Grade 3 to 4 granulocytopenia and thrombocytopenia occurred after 70% and 31% of courses administered, respectively. No grade 3 to 4 non-hematological toxicities were observed. Grade 1 or 2 nonhematological toxicities (in percentage of patients) consisted of nausea (41%, 8%) and vomiting (25%, 11%), and alopecia (100%)., Conclusion: TPT at the dose and schedule used has modest antitumor activity in SCLC patients refractory to etoposide and cisplatin, which indicates that clinical resistance to the topoisomerase II poison etoposide does not confer cross-sensitivity to the topoisomerase I poison TPT. TPT is well tolerated, with myelosuppression of short duration being the most common and limiting toxicity.

Purpose: This study was designed to assess the anti-tumor activity of topotecan (TPT) in patients with advanced non-small-cell lung cancer (NSCLC) previously untreated with chemotherapy., Patients and Methods: Patients with stage IIIB or IV NSCLC with measurable disease in nonradiated fields were eligible. Other eligibility criteria were Zubrod performance status (PS) < or = 2 and adequate renal and liver function. TPT was administered at a dose of 1.5 mg/m2/d for 5 days over 30 minutes every 21 days. Of 48 registered patients, 40 were fully assessable. Nineteen patients had adenocarcinoma (AD), 14 squamous carcinoma (SCC), and seven poorly differentiated carcinoma., Results: Six patients (15%) achieved a partial remission (PR) (durations: 8, 14, 18, 28, 56, and 61 weeks) and four patients a minor response; 10 patients had stable disease and 20 patients progressive disease. The PR rate was 36% (five of 14 patients) in patients with SCC versus 4% (one of 26 patients) in those with other histologies (P = .014). The overall median survival time was 38 weeks and 30% of patients were alive at 1 year. Grade 3 to 4 granulocytopenia and thrombocytopenia occurred after 76% and 10% of courses administered, respectively. No grade 3 to 4 nonhematologic toxicities were observed. Grade 1 or 2 nonhematologic toxicities consisted of nausea (46% and 5%), vomiting (31% and 7%), and fatigue (53% and 16%)., Conclusion: TPT at the dose and schedule used has moderate antitumor activity in NSCLC; its activity is mostly limited to patients with SCC. TPT is well tolerated, with myelosuppression of short duration being the most common and limiting toxicity.

Purpose: Sequencing and timing of chemotherapy and radiotherapy for limited small-cell lung cancer (LSCLC) was studied in two consecutive trials., Methods and Materials: In the interdigitating (IDG) trial, three cycles of COPE (cyclophosphamide 750 mg/M2 i.v. Day 1, vincristine 2 mg i.v. Day 8, cisplatin [DDP] 20 mg/M2 Days 1-3, etoposide 100 mg/M2 i.v. Days 1-3), were followed by thoracic radiation therapy (1.5 Gy bid 5-6 h apart, repeated twice at 3-week intervals) to give 45 Gy in 9 weeks; COPE was given during the intervals and for two more cycles. Operable patients had thoracotomy followed by IDG. Prophylactic cranial irradiation (PCI), 2.0 Gy x 15 fractions with a total dose of 30 Gy in 3 weeks, was given to the complete responders (CR) after completion of chemotherapy. In the concurrent (CON) trial, patients received DDP 60 mg/M2 i.v. Day 1, and etoposide 120 mg/M2 i.v. Days 1-3 for four cycles, every 3 weeks, and concurrent thoracic radiation therapy to 45 Gy with either 1.8 Gy daily, for 5 weeks or 1.5 Gy bid for 3 weeks. Prophylactic cranial irradiation (PCI) was given to the complete responders, 2.5 Gy daily for 2 weeks (25 Gy) (approximately 3 months after the initiation of treatment)., Results: The IDG group had 28 evaluable patients with median follow-up of 17.5 months. The CON group had 33 evaluable patients with median follow-up of 21 months. Overall survival rates for IDG patients were 79% at 1 year, 39% at 2 years, 30% at 3 years, and 27% at 4 years compared to 93%, 70%, 51%, and 46%, respectively, for the patients treated with CON (p = 0.01). Loco-regional recurrence (44%) and distant metastasis (48%) was more frequent as the first site of failure in the IDG group compared to the CON group (30% and 30%, respectively). Brain metastases constituted 30% of first metastases with IDG compared to none with CON. Esophagitis was significantly greater with CON. Hematologic and pulmonary toxicity were similar with IDG and CON. One death due to infection was seen in each treatment group., Conclusion: Concurrent chemoradiotherapy appears to be more effective than IDG. Earlier administration of PCI with concurrent chemotherapy and thoracic irradiation may reduce the risk of brain metastasis.

Recent evidence suggests that deficient HLA Class I expression in SCLC lines may be due, in part, to down-regulation of TAP-1 and TAP-2 expression, and, thus, deficient antigen processing. Given the capability of the multidrug transporter mediating MDR, P-gp, to transport peptides, we hypothesized that P-gp may substitute for TAP-1/TAP-2 and enhance antigen processing in SCLC. To investigate this, we studied the H69 line (parent SCLC) and VPR-2 (MDR subline selected in etoposide, P-gp +). HLA-A,B,C expression was significantly increased in VPR-2 cells relative to H69, and was much more inducible with IFN-gamma. TAP-1 and TAP-2 were expressed at low levels in both lines. Differential induction of TAP-1 expression with IFN-gamma exposure was observed, with a dramatic increase in VPR-2 cells, and no change in H69. TAP-2 expression was enhanced in both lines with IFN-gamma, but to a greater degree in VPR-2. VPR-2 cells were resistant to LAK killing relative to H69, and were minimally sensitized with IFN-gamma. In contrast, IFN-gamma enhanced susceptibility of H69 to LAK killing 3-fold. The direct correlation between enhancement of HLA-A,B,C expression by IFN-gamma and the differential inducibility of TAP-1 and TAP-2 expression in P-gp-SCLC lines is novel. Relative LAK sensitivity of H69 and its increase by IFN-gamma may have clinical implications.

Retinoic acid and interferon-alpha have limited single-agent activity in advanced cancer. Cell culture data indicate that in combination these agents have enhanced activity (modulating growth and differentiation) in a number of malignant cell types. Recent clinical work in advanced squamous cell carcinoma reports major activity with this regimen. This paper reviews the preclinical and clinical data testing retinoic acid in combination with interferons and presents recent work integrating these agents with radiotherapy in locally advanced cervical cancer.

We developed a multidrug resistant small cell lung cancer line, VPR-2, by exposing H69 parent cells to etoposide (20 microM) for 1 h daily for 3 days every 21-28 days, a schedule similar to that used in the clinic. Resistance (20-fold) to the cytostatic and DNA cleavage activities of etoposide emerged after the third treatment, and this phenotype was stable in the absence of drug exposure for 2.5 years. VPR-2 cells exhibited cross resistance to intercalating agents and vinca alkaloids, but remained sensitive to X-radiation, cisplatin and 5-fluorouracil. The human mdr1 gene was overexpressed in the resistant line, but steady-state concentrations of etoposide were reduced only 1.5-fold. Topoisomerase II catalytic and etoposide stimulated DNA cleavage activity in nuclear extracts from both lines were identical despite retention of a 3-fold level of resistance to etoposide-induced strand breaks in isolated nuclei from VPR-2 cells. Cyclosporin A and verapamil, both of which bind to P-glycoprotein, enhanced accumulation of etoposide in VPR-2 cells, and H69 cells to a lesser extent. Yet only cyclosporin A was effective in differentially enhancing etoposide cytostasis in VPR-2 relative to H69. In VPR-2 whole cells, cyclosporin A enhanced etoposide-induced DNA single-strand break frequency 9-fold but had no effect in isolated nuclei. Rapid selection of this line with a clinically relevant drug exposure schema and stability of the resistant phenotype suggest these cells may have been a steady subpopulation of the parent line through years of serial passage in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of multimodality therapy was conducted incorporating adjuvant resection in patients who presented with limited small-cell lung cancer (SCLC). This preliminary report addresses the resectability rate after induction chemotherapy. Twenty-five patients (1 with Stage II, 12 with Stage IIIa, and 12 with Stage IIIb disease) completed the induction regimen of 3 cycles of intravenous cyclophosphamide 750 mg/m2 on day 1, vincristine 2 mg on day 3, cisplatin 20 mg/m2 on days 1-3, and etoposide 100 mg/m2 on days 1-3, (every 3-4 weeks). Patients with complete response or partial response, 10 (40%) and 14 (56%) patients, respectively, were considered for surgical resection. Six were ineligible for surgery because of medical or surgical contraindications, and four refused surgery. Of the 14 patients taken to surgery, 10 had resectable disease (40% of the original group of 25). Three pneumonectomies, two bi-lobectomies, two lobectomies, and two wedge resections were performed. In the remaining patient multiple biopsies revealed no residual disease and resection was not performed. Surgery-related complications included one death, one bronchopleural fistula, and one episode of pneumonia. Induction chemotherapy was generally well tolerated. These preliminary data demonstrate that a significant percentage of patients with SCLC, Stages II-IIIb, can feasibly be resected after response to brief induction chemotherapy.

Fourteen patients with extensive disease small cell bronchogenic carcinoma (SCBC) received ifosfamide at 2,000 mg/m2/day for 5 consecutive days with simultaneous mesna and vincristine while 26 patients with extensive disease non-small-cell bronchogenic carcinoma (N-SCBC) received the same regimen without vincristine. Eight partial responses (57%) were observed with a 40-week median survival in the case of SCBC and four partial remissions (15%) with a 31-week median survival in N-SCBC. Granulocytopenia was the dose-limiting toxicity, whereas urotoxicity was well controlled with mesna. Neuropsychiatric toxicity consisted of anxiety, agitation, confusion, and hallucination. Neurobehavioral testing detected worsened performance during ifosfamide treatment. Ifosfamide is one of the few active agents in N-SCBC.

Twenty-six patients with a limited-disease presentation of small-cell bronchogenic carcinoma (SCBC) had surgery after achieving a partial remission with three cycles of chemotherapy. Persistent SCBC was found in 15 patients (58%), non-small-cell bronchogenic carcinoma (NSCBC) in six patients (23%), and no malignancy in five patients (19%). Twelve patients have died since surgery. Tumor-node-metastasis (TNM) staging prior to or after chemotherapy was not predictive of outcome, but an N0 status found at pathological examination of the surgical specimen was predictive of long-term survival. Median survival for this group of patients was 25 months. Adjuvant surgery is feasible and may be beneficial.

Evidence from several in vitro systems indicates that cellular responses to DNA topoisomerase II-reactive compounds (i.e., the epipodophyllotoxins and intercalating agents) may be affected by the relative rate of proliferation. Using a human head and neck squamous carcinoma cell line 183A, we have investigated the effect of beta-all-trans-retinoic acid (RA), a substance with known antiproliferative effects, on the DNA cleavage and cytotoxic activities of etoposide and 4'-(acridinylamino)methanesulfon-m-anisidide which interact with topoisomerase II. The effect of RA treatment on the activity of X-radiation and bleomycin, both of which produce free radical mediated effects, was also examined. RA treatment (10 to 20 microM for 72 h) does not significantly influence DNA cleavage induced by X-radiation or bleomycin but decreases DNA cleavage and cytotoxicity mediated by etoposide and 4'-(acridinylamino)methanesulfon-m-anisidide. Further, this effect can be demonstrated at a dose of RA that is minimally growth inhibitory. The inhibitory effect of RA appears to be localized to the nucleus given that similar effects on drug-mediated DNA cleavage can be demonstrated in nuclei isolated from RA-treated cells. However, both drug-stimulated DNA cleavage activity and topoisomerase II catalytic activity are approximately equal in crude nuclear extracts of untreated and RA-treated cells. These data suggest that the resistance to topoisomerase II-reactive drugs induced by RA treatment of 183A cells is not mediated through a direct effect on the enzyme, but, instead, is related to other changes in the nuclear milieu occurring in the initial stages of quiescence such as altered chromatin conformation.

Fourteen evaluable patients with small cell bronchogenic carcinoma received tiazofurin, an inhibitor of inosine monophosphate dehydrogenase, that progressed after one combination chemotherapy. No objective remission was observed at the dosage of 800 mg/m2 for 5 consecutive days. Toxicity was moderate.

Identification of DNA topoisomerase II as the intracellular target for the DNA cleavage activity of the epipodophyllotoxins and several intercalating agents is well established. In contrast, definite correlation of cleavable complex formation with eventual cell death has been more difficult to document. Our studies with an epipodophyllotoxin resistant cell line not only provide additional evidence that the enzyme is a multi-drug target, but also implicate drug-stimulated cleavage activity as a critical component of cytotoxic effect. When compared to WT (wild type) cells, the mutant Chinese hamster ovary cell line, VpmR-5, exhibits marked resistance to both the cytotoxic and DNA cleavage activity of etoposide as well as various intercalating agents. Steady state concentrations of these drugs in both cell lines is identical. Enzyme content as measured by immunoblot and by total decatenation activity in crude nuclear extracts is equal. Catalytic activity is also equally sensitive to inhibition by etoposide. In contrast, cleavage activity in purified enzyme from VpmR-5 cells is profoundly resistant to stimulation by drug. These data indicate that a multi-drug resistant phenotype may be acquired by a qualitative change in the enzyme that alters its interaction with drug. Further, the data strongly support a direct role for cleavable complex formation in cell death.

Based on the observation that VP-16-induced DNA damage can be demonstrated in isolated nuclei but not in purified DNA, and that this effect is temperature-dependent, it is postulated that the mechanism of action of VP-16 involves an essential intranuclear event, perhaps enzyme-mediated, which is a prerequisite for the cleavage of DNA. Using alkaline elution to assay single-strand breaks in isolated L1210 nuclei, we have further characterized conditions influencing this putative intranuclear reaction. We have found drug activity to be dependent on magnesium and pH and to be stimulated by low concentrations of ATP (0.05-1 mM), an effect which was not observed with a nonhydrolyzable analog of ATP. Heat-labile activity in a nuclear non-histone protein extract was critical to VP-16-mediated DNA damage. This new evidence lends further credence to the hypothesis that activity of an intranuclear enzyme, possessing characteristics consistent with a type II DNA topoisomerase, is a prerequisite for the cleavage of DNA by VP-16.

The mechanism of action of 4'-demethylepipodophyllotoxin-9-(4,6-O-ethylidene-beta-D-glucopyra noside) (VP-16), an important antitumor agent, is unclear. There is evidence that DNA may be the target of action because VP-16 causes single-strand and double-strand breaks in DNA and produces cytotoxicity over a similar dose range. We have hypothesized that an enzyme system, such as dehydrogenase, catalyzes an oxidation-reduction reaction involving the pendant phenolic group which forms an active metabolite that causes the DNA damage and cytotoxicity. To test our hypothesis, we investigated the effect of disulfiram, an aldehyde dehydrogenase inhibitor, and its metabolite, diethyldithiocarbamate, on VP-16-induced DNA damage in L1210 cells. Using the alkaline elution technique to assay DNA damage, we found that disulfiram and diethyldithiocerbamate inhibited VP-16-induced single-strand breaks. Both compounds were also capable of significantly reducing VP-16-induced cytotoxicity. Oxalic acid, pyrophosphate, and malonic acid, competitive inhibitors of succinate dehydrogenase, and the naturally occurring dehydrogenase substrates, succinic acid, beta-glycerophosphate, and isocitric acid, also blocked the effects of VP-16. Free-radical scavengers were also studied. While sodium benzoate was particularly effective in preventing drug-induced DNA damage and cytotoxicity, a number of other scavengers were not. Our data are consistent with the hypothesis that VP-16 is activated by an enzyme such as a dehydrogenase which transforms it into an active intermediate resulting in DNA damage and, consequently, cell death.

We have examined the relationship between topoisomerase II content and the DNA cleavage activity and cytotoxicity of etoposide during proliferative and quiescent culture conditions. In proliferating cultures of Chinese hamster ovary (CHO) cells, human lymphoblastic CCRF cells, and mouse leukemia L1210 cells, there was easily detectable topoisomerase II by immunoblotting. In contrast, quiescent CHO cells contained virtually no detectable topoisomerase II, while the content of L1210 cells was unchanged. Enzyme content of quiescent CCRF cells was diminished but detectable. DNA cleavage activity induced by etoposide correlated well with enzyme content in proliferating and quiescent cells. Quiescent CHO and CCRF cultures were highly resistant to the cytotoxic effects of etoposide as expected. However, despite unchanged enzyme content and DNA cleavage activity, there was also significant resistance observed in plateau L1210 cells. We have also investigated topoisomerase content and drug activity as a function of cell cycle progression. Following serum stimulation of confluent BalbC/3T3 cells, maximal etoposide-induced DNA cleavage activity is observed in G2/M and is associated with an increase in topoisomerase II content. Maximum cytotoxicity, however, occurs during mid to late S phase. Our data suggest that topoisomerase II content may be an important determinant of chemotherapeutic sensitivity during alterations in the proliferative status of the cell. However, it is clear that other factors must be involved in cell sensitivity, and elucidation of these may contribute to our understanding of the mechanism of action of these drugs.

Topoisomerase II mediated DNA scission induced by both a nonintercalating agent [4'-demethylepipodophyllotoxin 4-(4,6-O-ethylidene-beta-D-glucopyranoside) (VP-16)] and an intercalator [4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA)] was studied as a function of proliferation in Chinese hamster ovary (CHO), HeLa, and mouse leukemia L1210 cell lines. Log-phase CHO cells exhibited dose-dependent drug-induced DNA breaks, while plateau cells were found to be resistant to the effects of VP-16 and m-AMSA. Neither decreased viability nor altered drug uptake accounted for the drug resistance of these confluent cells. In contrast to CHO cells, plateau-phase HeLa and L1210 cells remained sensitive to VP-16 and m-AMSA. Recovery of drug sensitivity by plateau-phase CHO cells was found to reach a maximum approximately 18 h after these cells regained exponential growth and was independent of DNA synthesis. DNA strand break frequency correlated with cytotoxicity in CHO cells; log cells demonstrated an inverse log linear relationship between drug dose (or DNA damage) and colony survival, whereas plateau-derived colony survival was virtually unaffected by increasing drug dose. Topoisomerase II activity, whether determined by decatenation of kinetoplast DNA, by cleavage of pBR322 DNA, or by precipitation of the DNA-topoisomerase II complex, was uniformly severalfold greater in log-phase CHO cells compared to plateau-phase cells.