Safety and efficacy of pralsetinib in RET fusion-positive non-small-cell lung cancer including as first-line therapy: update from the ARROW trial.

BACKGROUND: RET fusions are present in 1%-2% of non-small-cell lung cancer (NSCLC). Pralsetinib, a highly potent, oral, central nervous system-penetrant, selective RET inhibitor, previously demonstrated clinical activity in patients with RET fusion-positive NSCLC in the phase I/II ARROW study, including among treatment-naive patients. We report an updated analysis from the ARROW study. PATIENTS AND METHODS: ARROW is a multi-cohort, open-label, phase I/II study. Eligible patients were ≥18 years of age with locally advanced or metastatic solid tumours and an Eastern Cooperative Oncology Group performance status of 0-2 (later 0-1). Patients initiated pralsetinib at the recommended phase II dose of 400 mg once daily until disease progression, intolerance, consent withdrawal, or investigator's decision. The co-primary endpoints (phase II) were overall response rate (ORR) by blinded independent central review and safety. RESULTS: Between 17 March 2017 and 6 November 2020 (data cut-off), 281 patients with RET fusion-positive NSCLC were enrolled. The ORR was 72% [54/75; 95% confidence interval (CI) 60% to 82%] for treatment-naive patients and 59% (80/136; 95% CI 50% to 67%) for patients with prior platinum-based chemotherapy (enrolment cut-off for efficacy analysis: 22 May 2020); median duration of response was not reached for treatment-naive patients and 22.3 months for prior platinum-based chemotherapy patients. Tumour shrinkage was observed in all treatment-naive patients and in 97% of patients with prior platinum-based chemotherapy; median progression-free survival was 13.0 and 16.5 months, respectively. In patients with measurable intracranial metastases, the intracranial response rate was 70% (7/10; 95% CI 35% to 93%); all had received prior systemic treatment. In treatment-naive patients with RET fusion-positive NSCLC who initiated pralsetinib by the data cut-off (n = 116), the most common grade 3-4 treatment-related adverse events (TRAEs) were neutropenia (18%), hypertension (10%), increased blood creatine phosphokinase (9%), and lymphopenia (9%). Overall, 7% (20/281) discontinued due to TRAEs. CONCLUSIONS: Pralsetinib treatment produced robust efficacy and was generally well tolerated in treatment-naive patients with advanced RET fusion-positive NSCLC. Results from the confirmatory phase III AcceleRET Lung study (NCT04222972) of pralsetinib versus standard of care in the first-line setting are pending.

Statistical controversies in clinical research: building the bridge to phase II-efficacy estimation in dose-expansion cohorts.

BACKGROUND: Regulatory agencies and others have expressed concern about the uncritical use of dose expansion cohorts (DECs) in phase I oncology trials. Nonetheless, by several metrics-prevalence, size, and number-their popularity is increasing. Although early efficacy estimation in defined populations is a common primary endpoint of DECs, the types of designs best equipped to identify efficacy signals have not been established. METHODS: We conducted a simulation study of six phase I design templates with multiple DECs: three dose-assignment/adjustment mechanisms multiplied by two analytic approaches for estimating efficacy after the trial is complete. We also investigated the effect of sample size and interim futility analysis on trial performance. Identifying populations in which the treatment is efficacious (true positives) and weeding out inefficacious treatment/populations (true negatives) are competing goals in these trials. Thus, we estimated true and false positive rates for each design. RESULTS: Adaptively updating the MTD during the DEC improved true positive rates by 8-43% compared with fixing the dose during the DEC phase while maintaining false positive rates. Inclusion of an interim futility analysis decreased the number of patients treated under inefficacious DECs without hurting performance. CONCLUSION: A substantial gain in efficiency is obtainable using a design template that statistically models toxicity and efficacy against dose level during expansion. Design choices for dose expansion should be motivated by and based upon expected performance. Similar to the common practice in single-arm phase II trials, cohort sample sizes should be justified with respect to their primary aim and include interim analyses to allow for early stopping.

Growth inhibition and induction of apoptosis by fenretinide in small-cell lung cancer cell lines.

BACKGROUND: Lung cancer is the major cause of cancer-related death in the United States, with small-cell lung cancer (SCLC) constituting approximately 20% of all cases of lung cancer. Numerous epidemiologic and molecular studies have suggested that alterations in retinoid-signaling pathways play a role in the pathogenesis of lung cancer. Fenretinide [N-(4-hydroxyphenyl)retinamide; HPR] is a synthetic retinoid with minimal toxicity and favorable pharmacokinetics during long-term administration to patients in clinical trials. PURPOSE: The aim of this investigation was to study the effect of HPR on the growth of SCLC cells in vitro. METHODS: Seven SCLC cell lines (NCI-H69, NCI-H82, NCI-H146, NCI-H209, NCI-H345, NCI-H446, and NCI-H510A) were exposed continuously to a broad range of concentrations of HPR or all-trans-retinoic acid (RA), and cell viability was determined on day 3 and day 7 by the trypan blue dye exclusion assay. The growth of these cells was compared with that of control vehicle-treated cells to determine survival fraction and the dose resulting in a 50% inhibition of growth when compared with growth of control cells (IC50). The induction of apoptosis was evaluated by fluorescent microscopy, DNA content analysis, and a terminal deoxyribonucleotidyl transferase-based assay that labels 3'-hydroxyl ends of DNA fragments (TUNEL assay) combined with flow cytometric analysis. RESULTS: HPR inhibited growth of a panel of SCLC cell lines at IC50 values that ranged from 0.1 to 3.0 microM (concentrations that are clinically achievable). In all cell lines tested, HPR was a more potent growth inhibitor than RA. By use of fluorescent microscopy, HPR was found to induce morphologic changes consistent with apoptosis in NCI-H82 SCLC cells, including cellular shrinkage, chromatin condensation, and nuclear fragmentation. Flow cytometric analysis revealed decreased DNA content, and TUNEL assay showed increased digoxigenin-uridine triphosphate incorporation in HPR-treated NCI-H82 SCLC cells; these findings are consistent with the induction of apoptosis. CONCLUSIONS: HPR inhibited the in vitro growth of SCLC cells. In NCI-H82 cells, HPR inhibited growth via the induction of apoptosis.

Mechanism of all-trans-retinoic acid-mediated L-myc gene regulation in small cell lung cancer.

The L-myc oncogene is commonly expressed in small cell lung cancer (SCLC) cells and is associated with SCLC cells with a high level of neuroendocrine differentiation and a relatively low proliferative index. We have previously reported that all-trans-retinoic acid (RA) inhibits the growth of NCI-H82 SCLC cells in association with increased neuroendocrine differentiation, increased L-myc gene expression and decreased c-myc gene expression. In the present report, the mechanism of RA-mediated L-myc up-regulation in NCI-H82 SCLC cells was determined by analysing transcriptional and post-transcriptional control of L-myc gene expression. Increases in steady-state levels of L-myc mRNA occurred in a dose-dependent manner after exposure to RA at a time-point prior to discernible changes in cellular morphology or growth. By nuclear run-on analysis, there was a clear increase in L-myc transcript initiation in NCI-H82 cells treated with 1 microM RA, but no alteration was noted in the baseline degree of transcript attenuation when compared to control cells. L-myc transcript half-life remained unchanged after exposure to 1 microM RA, indicating that post-transcriptional regulation is not a major factor in the control of L-myc gene expression. A marked dose-dependent increase in RARbeta expression was also demonstrated in RA-treated NCI-H82 cells. We conclude that RA-mediated up-regulation of L-myc gene expression occurs through stimulation of transcript initiation and that the biological effects of RA in SCLC cells may be mediated through RARbeta-dependent pathways.

Loss of heterozygosity on the long arm of human chromosome 7 in sporadic renal cell carcinomas.

Cytogenetic and molecular analysis of DNA sequences with highly polymorphic microsatellite markers have implicated allele loss in several chromosomal regions including 3p, 6p, 6q, 8p, 9p, 9q, 11p and 14q in the pathogenesis of sporadic renal cell carcinomas (RCCs). Deletions involving the long arm of chromosome 7 have not been described in RCCs although they have been seen in several other tumor types. However, there have been no detailed analysis of loss of heterozygosity (LOH) of 7q sequences in sporadic RCCs. We therefore studied LOH for DNA sequences on 7q with 10 highly polymorphic markers in 92 matched normal/tumor samples representing sporadic RCCs including papillary, nonpapillary, and oncocytomas in order to determine whether allelic loss could be detected in a tumor type with no visible 7q rearrangements at the cytogenetic level. We found chromosome 7q allele loss in 59 of 92 cases (64%) involving one, two, or more microsatellite markers. The most common allele loss included loci D7S522 (24%) and D7S649 (30%) at 7q31.1-31.2, a region that contains one of the common fragile sites, FRA7G. By comparative multiplex PCR analysis, we detected a homozygous deletion of one marker in the 7q 31.1-31.2 region in one tumor, RC21. These results support the idea that a tumor suppressor gene in 7q31 is involved in the pathogenesis of sporadic renal cell carcinomas.

Lung cancer in young patients: analysis of a Surveillance, Epidemiology, and End Results database.

PURPOSE: A large community-based cancer registry was analyzed to determine if the clinicopathologic characteristics and/or survival rates of lung cancer patients under 50 years of age at diagnosis differ from those of patients 50 years of age or greater at diagnosis. PATIENTS AND METHODS: Data regarding demographics, stage, histology, initial therapy, and survival were obtained on all patients with primary bronchogenic carcinoma registered in the metropolitan Detroit Surveillance, Epidemiology and End Results (SEER) registry from 1973 to 1992. RESULTS: Of 31,266 patients, 9.0% were under 50 years of age at diagnosis. Females (40.1% v 31.2%; P < .001) and blacks (28.7% v 21.9%, P < .001) were overrepresented in the younger group compared with the older group. Younger patients had a significantly higher incidence of adenocarcinoma and were less likely to present with local-stage disease (18.6% v 25.2%; P < .001). Younger patients were significantly more likely to undergo surgery and/or combined-modality therapy. Relative survival at 5 years was significantly better in the younger group (16.1% v 13.4%; P < .001), mainly because of better survival in patients with local-stage disease (48.7% v 35.4%; P < .001). In a multivariate analysis, advanced-stage, nonsurgical initial therapy, age 50 years or greater at diagnosis, and male gender were independent negative prognostic factors. CONCLUSION: The overrepresentation of females and blacks in the group of younger patients with lung cancer suggests an increased susceptibility to lung carcinogens in these populations. Overall, this study suggests that lung cancer is not a more aggressive disease in younger patients and that all patients with lung cancer should be managed along the same therapeutic guidelines.

Inhibition of tumor cell growth by p21WAF1 adenoviral gene transfer in lung cancer.

Gene replacement therapy is potentially a very powerful tool, targeting specific molecular mediators of cancer development and progression. p21WAF1 (p21) is a cyclin-dependent kinase inhibitor that is induced by p53 upon DNA damage or p53 overexpression, resulting in cell cycle arrest at the G1 checkpoint and inhibition of further cell proliferation. Using a replication-deficient recombinant adenovirus (AdV) ((rAd)-p21) as a p21 gene delivery system, we have evaluated the effect of p21 introduction in lung cancer cells in vitro as well as in vivo. In in vitro experiments, two human non-small cell lung cancer (NSCLC) cell lines, NCI-H460 and NCI-H322, showed dose-dependent p21 induction and concomitant cell growth inhibition following rAd/p21 infection. Flow cytometric analysis of the cell cycle revealed a significant increase in the percentage of NCI-H460 cells in G0/G1 following rAd/p21 infection compared with untreated cells, suggesting that p21-induced growth inhibition was due to G0/G1 arrest. We also tested the therapeutic efficacy of rAd/p21 in an in vivo human NSCLC model in SCID mice. Tumor-bearing mice were established by subcutaneous injections of NCI-H460 cells and treated by repeated intratumoral injections of rAd/p21. Intratumoral delivery of rAd/p21 significantly suppressed tumor growth and prolonged survival in rAd/p21-treated mice. Our in vitro and in vivo results provide strong preliminary evidence for the growth inhibition of NSCLC by rAd/p21. Collectively, these results justify further studies to evaluate the efficacy of rAd/p21 for gene therapy in human lung cancer.

Tumor lysis syndrome in small cell carcinoma and other solid tumors.

OBJECTIVE: To review the risk factors and clinical findings associated with tumor lysis syndrome (TLS) in patients with small cell carcinomas and other solid tumors. METHODS: Reports of TLS in the English-language literature were identified by searching MEDLINE and the bibliographies of relevant case reports, journal articles, and book chapters. All reports identified through these searches, including abstracts from national meetings, were reviewed and included in this analysis. Data regarding clinical and biochemical parameters relevant to the occurrence of TLS were extracted from each report. RESULTS: Of the 25 reported solid tumor patients who developed TLS, 7 had small cell carcinoma, 5 breast cancer, and 4 neuroblastoma. TLS was associated with a variety of treatment regimens, including chemotherapy, immunotherapy, hormonal therapy, radiation therapy, and surgery. Common risk factors for TLS in this population included pretreatment renal insufficiency, elevated serum lactate dehydrogenase (LDH), and hyperuricemia. Among the typical biochemical findings of TLS, acute renal insufficiency and hyperuricemia were identified in nearly all patients and hyperkalemia, hyperphosphatemia, hypocalcemia, and increased serum LDH were reported in over 75% of patients. In addition, seven patients, including the current case, presented with profound metabolic acidosis. Nine of 25 patients died during the acute episode of TLS. CONCLUSIONS: Although TLS occurs infrequently in patients with solid tumors, the risk factors and biochemical abnormalities associated with this potentially fatal complication of therapy must be recognized to allow for adequate monitoring and early initiation of appropriate therapeutic measures.

Effect of v-rasH on sensitivity of NCI-H82 human small cell lung cancer cells to cisplatin, etoposide, and camptothecin.

Expression of v-ras(H) in NCI-H82 human small cell lung cancer (SCLC) cells results in a line (NCI-H82ras(H)) with a non-small cell phenotype (Mabry et al., Proc Natl Acad Sci USA 85: 6523-6527, 1988). This v-ras(H) -associated phenotypic change is prevented by treatment with trans-retinoic acid (tRA) (Kalemkarian et al., Cell Growth Differ 5: 55-60, 1994). The present studies were performed to examine changes in drug sensitivity that accompanied these phenotypic changes. v-ras(H) expression was associated with increased metallothionein-IIa (MT-IIa) mRNA and decreased levels of nonprotein sulfhydryls in NCI-H82ras(H) cells compared with -H82 cells. These changes were accompanied by the development of CdCl2 resistance without any change in cisplatin sensitivity. In contrast, growth of parental NCI-H82 cells in 1 microM tRa resulted in increased MT-IIa mRNA without any change in nonprotein sulfhydryls. In these cells, a 3.3-fold increase in cisplatin IC50 was observed. Examination of the action of topoisomerase (topo) poisons revealed that NCI-H82 and -H82ras(H) cells had indistinguishable levels of topo II polypeptides and indistinguishable sensitivities to etoposide, an agent that is often combined with cisplatin clinically. On the other hand, v-ras(H) expression was accompanied by a 2-fold increase in topo I activity and a 1.7-fold decrease in IC50 for the topo I-directed agent camptothecin. These changes resulted in 30-fold lower survival of NCI-H82ras(H) cells compared with -H82 cells at camptothecin concentrations as low as 10 nM. In summary, these studies demonstrate that chronic tRA treatment is accompanied by decreased cisplatin sensitivity in NCI-H82 human SCLC cells. In contrast, v-ras(H) expression is not associated with any change in cisplatin or etoposide sensitivity, but is accompanied by increased camptothecin sensitivity.

Therapeutic advances in small cell lung cancer.

Small cell lung cancer (SCLC) is characterised by neuroendocrine differentiation, early metastatic potential and initial responsiveness to cytotoxic therapy. Unfortunately, despite recent therapeutic advances, most patients relapse and the overall five-year survival rate is only 5%. Standard treatment of SCLC consists of platinum-based combination chemotherapy, with thoracic irradiation added for patients with limited-stage disease. Several newer chemotherapeutic drugs have recently been shown to have significant activity in patients with untreated or relapsed SCLC. These agents include: the topoisomerase I inhibitors, topotecan and irinotecan; the taxanes, paclitaxel and docetaxel; the pyrimidine analogue, gemcitabine; and the vinca alkaloid, vinorelbine. Recent advances in our understanding of the molecular events involved in the pathogenesis and progression of SCLC have led to the identification of a variety of potential targets for novel therapeutic interventions. Strategies aimed at inhibiting the myriad of growth factor pathways that control the proliferation of SCLC cells, include: broad spectrum neuropeptide antagonists (e.g., substance P analogues); growth factor/receptor-specific inhibitors (e.g., anti-GRP monoclonal antibodies, bradykinin antagonist dimers); and a variety of selective protein kinase inhibitors. The importance of cell death pathways in carcinogenesis and treatment-resistance has led to several novel strategies targeting apoptotic mediators, such as bcl-2, that are frequently dysregulated in SCLC (e.g., bcl-2 antisense). Our current challenges are to further refine these promising therapeutic strategies, efficiently evaluate their activity in the clinical setting and integrate them into more effective treatment regimens to improve the overall prognosis of patients with SCLC.

Impact of race in lung cancer: analysis of temporal trends from a surveillance, epidemiology, and end results database.

STUDY OBJECTIVES: We analyzed data from a community-based cancer database over a 26-year period in order to characterize clinicopathologic differences between black and white patients with lung cancer, and to identify relevant temporal trends in incidence and survival. DESIGN, SETTING, AND PATIENTS: Data on demographics, stage, histology, and survival were obtained on all black and white patients with primary bronchogenic carcinoma registered in the community-based metropolitan Detroit Surveillance, Epidemiology, and End Results database from 1973 to 1998. RESULTS: Of 48,318 eligible patients, 23% were black. Lung cancer incidence rates decreased for men of both races from 1985 to 1998, with a greater decline occurring in black men (p < 0.0001). Although incidence rates declined over time for men of both races < 50 years of age, this decrease was greater in white men, resulting in an increase in the racial differential in younger men. Temporal trends in incidence rates were similar for women of both races. The incidence of distant-stage disease was higher among blacks throughout the study period. The incidence of local-stage disease decreased for both races, though this decline was greater in blacks. A significant racial difference in 2-year and 5-year survival rates developed during the study period, due to a distinct lack of improvement in black patients. In a multivariate model, the relative risks of death for black patients, relative to white patients, were 1.24 (p < 0.0001) for local stage, 1.14 (p < 0.0001) for regional stage, and 1.03 (p = 0.045) for distant stage. CONCLUSION: Significant racial differences exist in the incidence and survival rates for lung cancer in metropolitan Detroit. Since 1973, several disturbing trends have developed, particularly with regard to the lack of improvement in overall survival in black patients. Further study is required to determine the factors responsible for these temporal trends.

Lung cancer in patients < 50 years of age: the experience of an academic multidisciplinary program.

OBJECTIVE: To determine if the clinicopathologic features and survival of lung cancer patients < 50 years of age differ from those of older patients. DESIGN: Retrospective review of patients with primary bronchogenic carcinoma diagnosed at a single, multidisciplinary cancer center. SETTING: A National Cancer Institute-designated comprehensive cancer center in urban Detroit, MI. PATIENTS: All patients with primary bronchogenic carcinoma evaluated in the Multidisciplinary Lung Cancer Clinic at the Barbara Ann Karmanos Cancer Institute between 1990 and 1993. RESULTS: Of 1,012 patients with lung cancer, 126 (12.5%) were < 50 years old at diagnosis, with a median age of 44 years. The median age of the 886 patients > or = 50 years of age was 65 years. The gender (p = 0.08) and racial (p = 0.12) characteristics of the younger and older patient groups were not significantly different. More than 90% of patients in both groups were smokers. The incidence of adenocarcinoma was significantly higher in younger patients (48.4% vs 36.0%, p < 0.001), and early-stage disease was less frequently diagnosed in younger patients (4.8% vs 19.7%, p < 0.001). Younger patients were more likely than older patients to undergo treatment, including surgery and combined-modality therapy (p < 0.001). Median survival was 13 months in younger and 9 months in older patients, while overall survival was similar in younger and older patients (p = 0.13). CONCLUSIONS: Although younger patients with lung cancer present with more advanced-stage disease, their overall survival is similar to that of older patients, suggesting that lung cancer is not an inherently more aggressive disease in patients < 50 years of age.

Etoposide-induced pulmonary toxicity.

After treatment with etoposide, two patients with lung cancer developed interstitial infiltrates and respiratory failure. Of the two, one patient responded rapidly to steroid therapy and developed recurrent symptoms on re-challenge with etoposide. Both patients had histopathologic findings consistent with drug-induced pulmonary toxicity. Etoposide-induced lung disease needs to be considered in patients who develop subacute dyspnea and interstitial infiltrates during treatment with this agent.

Phase I trial of concurrent thoracic radiation and continuous infusion cisplatin and etoposide in stage III non-small cell lung cancer.

OBJECTIVE: Although combined modality therapy appears to be superior to radiotherapy alone for the treatment of locally advanced non-small cell lung cancer (NSCLC), the optimal treatment regimen has not been determined. We designed this trial to determine the maximal tolerated doses (MTD) of continuous intravenous infusion (CI) cisplatin and etoposide that could be administered concurrently with thoracic irradiation. METHODS: 19 patients with stage IIIA or IIIB NSCLC were treated at three different dose levels of CI cisplatin and etoposide with concurrent single daily fraction thoracic radiotherapy to 4500 cGy. This chemoradiotherapy phase of treatment was followed by a 1500-2000 cGy radiotherapy boost and three cycles of standard intermittent bolus cisplatin 80 mg/m2 i.v. on day 1 and etoposide 80 mg/m2 i.v. on days 1, 2 and 3. RESULTS: The MTD of CI chemotherapy was determined to be cisplatin 5 mg/m2/day plus etoposide 18 mg/m2/day for 5 days per week over 5 weeks along with thoracic irradiation. Overall, 37% of patients required breaks in the chemoradiotherapy course and 32% required attenuation of the planned duration of CI chemotherapy. Only 42% of patients received all three planned cycles of bolus chemotherapy and 16% received < 6000 cGy of thoracic irradiation. The major toxicities during concurrent chemoradiotherapy were grade 3-4 esophagitis (42%) and myelosuppression (47%). Subsequent chemotherapy was complicated by grade 3-4 myelosuppression in 38% of patients. An objective response was documented in 58% of patients (CR 11%, PR 47%). Median survival was 18 months with 2- and 5-year survival rates of 42 and 11%, respectively. CONCLUSIONS: These results demonstrate that CI cisplatin and etoposide can be administered safely to patients with locally advanced NSCLC, and that such potentially radiosensitizing strategies deserve further evaluation in this setting.

Phase II study of hyperfractionated radiotherapy and concurrent weekly alternating chemotherapy in limited-stage small cell lung cancer.

Despite recent advances in combined modality therapy, long-term survival remains elusive in most patients with limited-stage small cell lung cancer (SCLC). The present study was designed to evaluate the activity and toxicity of concurrent hyperfractionated radiotherapy and weekly, alternating-regimen chemotherapy. Twelve patients with limited-stage SCLC and performance status 0-1 were treated with cyclophosphamide 250 mg/m2, etoposide 100 mg/m2, and cisplatin 50 mg/m2 on day 1 every other week, and vincristine 1 mg/m2 on day 8, and ifosfamide 1.2 mg/m2 on days 8 and 9 every other week. Hyperfractionated thoracic radiotherapy, consisting of three daily doses of 1.1 Gy for 20 days to a total dose of 66 Gy, was started on day 1 of chemotherapy. Ten patients (83%) exhibited an objective response (9 CRs and 1 PR) with a median duration of response of 8.6 months. Two complete responders died at 50 and 53 months without evidence of progression and two remain alive and free of SCLC at 73 and 87 months. Median survival was 19.8 months with 2- and 5-year survival rates of 50 and 17%, respectively. Severe toxicity, including grade 3-4 esophagitis (67%) and granulocytopenia (83%), as well as debilitating fatigue and pneumonitis, prompted early termination of the trial. Hyperfractionated radiotherapy and concurrent weekly alternating-regimen chemotherapy resulted in promising response and survival rates, but induced excessive toxicity, in patients with limited-stage SCLC.

Induction of apoptosis by a short-chain neuropeptide analog in small cell lung cancer.

Small cell lung cancer (SCLC) cells express a variety of neuropeptides which act as autocrine growth factors. Although several neuropeptide analogs have been reported to antagonize SCLC proliferation, the development of these compounds has been limited by their low potency and the cytostatic nature of their effects. In the present study we evaluated the cytotoxic activity of four short-chain substance P analogs (NY3460, NY3238[-pHOPA], NY3238[Phe1], NY3238[Lys5]) against a panel of five SCLC cell lines. NY3460 was the most potent compound in all five SCLC cell lines (IC50 = 2.8-3.7 microM) as assessed by a MTT growth inhibitory assay. NY3238[Phe1] was also relatively active in all cell lines (IC50 = 3.5-11.2 microM), while NY3238[Lys5] and NY3238[-pHOPA] were substantially less active. NY3460 was the only agent to induce an increase in the percentage of cells with subdiploid DNA content suggestive of apoptosis by flow cytometric DNA content analysis. The induction of apoptosis was confirmed by fluorescent microscopy in NCI-H69, NCI-H82, NCI-H446, and NCI-H510 cells after exposure to 5.0 microM NY3460 for 48 h. These findings suggest that NY3460 is a relatively potent cytotoxic inhibitor of SCLC growth, and that short-chain neuropeptide analogs deserve further evaluation as anti-SCLC agents.

Activity of fenretinide plus chemotherapeutic agents in small-cell lung cancer cell lines.

PURPOSE: Fenretinide [N-(4-hydroxyphenyl)retinamide, 4HPR], a synthetic retinoid, is a potent inducer of apoptosis in small-cell lung cancer (SCLC) cell lines that may act through the generation of reactive oxygen species, suggesting that it may enhance the activity of other cytotoxic agents. In light of 4HPR's clinical potential and potent activity against SCLC cells, we evaluated the in vitro activity of 4HPR in combination with cisplatin, etoposide or paclitaxel. METHODS: The growth-inhibitory activities of single-agent 4HPR, cisplatin, etoposide or paclitaxel, and combinations of 4HPR and individual chemotherapeutic agents, were evaluated using an MTT assay in two SCLC cell lines. Each two-drug combination was studied over a range of concentrations at a fixed ratio corresponding to the ratio of the IC5 values of the individual agents. Data were analyzed by median-effect analysis as previously applied to drug combination studies. RESULTS: All four agents inhibited growth in a dose-dependent manner in the NCI-H82 and NCI-H446 SCLC cell lines. At clinically reported drug concentrations that resulted in over 50% growth inhibition, the activities of the combinations 4HPR and cisplatin and 4HPR and etoposide were more than additive in both cell lines, and the activity of 4HPR plus paclitaxel was more than additive in NCI-H446 cells. CONCLUSION: 4HPR's potent single-agent activity, minimal toxicity, and potential synergy with standard cytotoxic drugs will allow for the development of promising investigational regimens for the treatment of patients with SCLC.

Activity of dolastatin 10 against small-cell lung cancer in vitro and in vivo: induction of apoptosis and bcl-2 modification.

PURPOSE: Dolastatin 10 is a natural cytotoxic peptide which acts through the inhibition of microtubule assembly. Studies have suggested that such agents can induce apoptosis in association with bcl-2 phosphorylation. Since bcl-2 overexpression is common in small-cell lung cancer (SCLC), we evaluated the activity of dolastatin 10 in SCLC cell lines and xenografts. METHODS: In vitro growth inhibition was evaluated with a standardized MTT assay and apoptosis with fluorescent microscopy and a TUNEL assay. Immunoblot analysis and phosphatase digestion were used to determine bcl-2 modification. In vivo activity was evaluated in subcutaneous and metastatic SCLC xenograft models in SCID mice. RESULTS: Dolastatin 10 had growth inhibitory activity against four SCLC cell lines (NCI-H69, -H82, -H446, -H510) with IC50 values ranging from 0.032 to 0.184 nM. All four cell lines exhibited evidence of apoptosis after 48 h of exposure to 1.3 nM dolastatin 10. Immunoblot analysis revealed that 1.3 nM dolastatin 10 altered the electrophoretic mobility of bcl-2 in NCI-H69 and -H510 cells within 16 h of treatment. Incubation of protein extract from dolastatin 10-treated NCI-H69 and -H510 cells with calcineurin resulted in the disappearance of the altered mobility species, suggesting dolastatin 10-induced bcl-2 phosphorylation. In in vivo studies, 450 microg/kg of dolastatin 10 IV x 2 given after intravenous injection of NCI-H446 cells completely inhibited tumor formation. In established subcutaneous NCI-H446 xenografts, 450 microg/kg of dolastatin 10 IV induced apoptosis in the majority of tumor cells within 96 h, resulting in a log10 cell kill of 5.2 and an increase in median survival from 42 to 91 days. CONCLUSIONS: These findings suggest that dolastatin 10 has potent activity against SCLC and that the modulation of apoptotic pathways deserves further evaluation as an anticancer strategy.

Induction of gastrin releasing peptide by all-trans retinoic acid in small cell lung cancer cells.

All-trans retinoic acid (RA) has been shown to inhibit cell proliferation while increasing neuroendocrine differentiation in small cell lung cancer (SCLC) cells. RA and related compounds are rapidly becoming integrated into clinical trials to prevent lung cancers and other aerodigestive neoplasms. We found that expression of gastrin releasing peptide (GRP), which can promote lung tumorigenesis in model systems, was increased by RA in SCLC cells which have functional retinoid signaling. In SCLC cells that possess functional GRP receptors, ectopic expression of RARc increased GRP expression and augmented cloning efficiency, demonstrating that these maneuvers result in biologically active GRP. SCLC cells with defects in RA pathway signaling did not efficiently induce GRP upon RA exposure. In these cells, transfection of RARs rendered the cells competent to induce GRP upon RA exposure. These data show that activation of intact retinoid signaling by RA can induce GRP, a growth factor that can act as a tumor promoter. Our findings suggest the possibility that retinoids may increase, rather than decrease, lung cancer risks in some individuals.

Dolastatin 15 induces apoptosis and BCL-2 phosphorylation in small cell lung cancer cell lines.

BACKGROUND: The dolastatins are natural peptides which inhibit microtubule assembly and induce apoptosis in a number of malignant cell types. In small cell lung cancer (SCLC), bcl-2 overexpression is very common and appears to be a mediator of cell growth and treatment-resistance, suggesting that bcl-2 is a rational target for novel anti-SCLC strategies. Since several other tubulin-binding agents have been reported to induce apoptosis in association with phosphorylation and inactivation of bcl-2, we evaluated the effects of dolastatin 10 and 15 in SCLC cells. METHODS: The growth inhibitory activity of dolastatin 10 and 15 was evaluated in four SCLC cell lines with an MTT assay. Cell cycle and the induction of apoptosis were evaluated by flow cytometry and fluorescent microscopy. Immunoblot analysis was used to determine bcl-2 expression and phosphorylation. RESULTS: Dolastatin 15 displayed growth inhibitory activity against all four SCLC cell lines (NCI-H69, NCI-H82, NCI-H345, NCI-H446) with IC50 values ranging from 0.039-28.8 nM, which were 2.7-9.2-fold higher than the values for dolastatin 10. All four SCLC cell lines underwent G2/M arrest within 24 hours of exposure to dolastatin 15, and three had morphologic evidence of apoptosis after 48 hours. Immunoblot analysis of dolastatin 15-treated cells which overexpressed bcl-2 revealed a pattern consistent with bcl-2 phosphorylation. CONCLUSION: Dolastatin 15 has in vitro activity against SCLC cells, but is less potent than dolastatin 10. This activity is associated with the induction of apoptosis and bcl-2 phosphorylation. These findings suggest that further evaluation of the activity of the dolastatins in SCLC is reasonable and that the pharmacologic modulation of apoptotic pathways deserves further study as a potential anticancer strategy.