Topoisomerase I inhibitors in the combined-modality therapy of lung cancer

Locally advanced non-small-cell lung cancer represents 30% to 40% of all pulmonary malignancies. Most patients will die of the disease after aggressive contemporary treatments. Therefore, significant improvement in therapeutic methods must be implemented to improve overall survival rates. The arrival of a new generation of chemotherapeutic agents--including the taxanes, gemcitabine (Gemzar), and topoisomerase inhibitors such as irinotecan (Camptosar) and topotecan (Hycamtin)--offers the hope of significant advances in the treatment of lung cancer. Irinotecan and topotecan are camptothecin derivatives that inhibit topoisomerase I enzyme. It is believed that topoisomerase I inhibitors stabilize a DNA/topoisomerase I complex and interact with replication machinery to cause cell death. A significant amount of data demonstrates that these topoisomerase I inhibitors also act as radiosensitizers. With the increasing data that support concurrent chemoradiation treatment for malignancies, including lung cancer and head and neck cancers, there is an impetus to pursue the additional drugs that may potentially improve local control and survival. Irinotecan is undergoing early clinical trials in the combined-modality setting in several different disease sites. This paper will review the data on the role of camptothecin derivatives as a radiosensitizer and as a component of combined-modality therapy for lung cancer. It is hoped that newer treatment strategies, like the combination of radiation and topoisomerase I inhibitors, will have a significant impact on cure rates in the future.

Enhancement of radiation effects by combined docetaxel and flavopiridol treatment in lung cancer cells

BACKGROUND AND PURPOSE

To evaluate the potential role and mechanism of docetaxel plus flavopiridol in modulating radiosensitivity in vitro and in vivo.

PATIENTS AND METHODS

In vitro. H460 human lung carcinoma cells were treated with docetaxel (10 nM for 1 h, at t = 0 h) --> radiation (0-5 Gy, at t = 6 h) --> flavopiridol (120 nM for 24 h, at t = 8 h). Colony forming ability was measured to assess the modulation of sensitivity. Cell cycle redistribution was measured by flow cytometric analysis using propidium iodide. Percent apoptosis was also measured by flow cytometric analysis using 7-amino-actinomycin D staining. In vivo. H460 cell xenografts were used in nude mice. Tumors were grown subcutaneously on the flank, then treated with docetaxel (2.5 mg/kg, at t = 0 h) --> radiation (2 Gy, at t = 6 h) --> flavopiridol (1.25 mg/kg, at t = 8 h) for 5 consecutive days. Tumor growth delay was then measured and compared with the control group.

RESULTS

Docetaxel plus flavopiridol enhanced the effect of radiation. The maximum radiopotentiation and apoptosis were observed when the cells were treated with the sequence of docetaxel-->radiation-->flavopiridol both in vitro and in vivo. Flavopiridol and docetaxel induced G1 and G2/M arrest, respectively.

CONCLUSIONS

This study shows that docetaxel plus flavopiridol enhances the effects of radiation in vitro and in vivo. Our data suggest that the mechanism of radiopotentiation by combining flavopiridol and docetaxel involves an enhancement of apoptosis and changes of cell cycle by docetaxel and flavopiridol.

Broad spectrum receptor tyrosine kinase inhibitor, SU6668, sensitizes radiation via targeting survival pathway of vascular endothelium

PURPOSE

Recent studies have demonstrated radiosensitization by inhibiting receptor tyrosine kinases (RTKs). Irradiation activates RTKs and their downstream prosurvival molecule, Akt. In this study, we investigated the mechanism by which SU6668, an inhibitor of RTKs involved in angiogenic pathways, enhances effects of irradiation.

METHODS AND MATERIALS

Western blots were used to determine Akt phosphorylation. Clonogenic assays were performed to determine endothelial survival after combination of SU6668 and irradiation. This combination therapy was also tested in mouse models with Lewis lung carcinoma or glioblastoma multiforme (GL261) for inhibition of tumor growth and tumor vasculature by examining tumor volume, tumor vascular window, and blood flow.

RESULTS

We found that SU6668 inhibited the Akt activation inducible by irradiation. Clonogenic survival of endothelial cells was decreased after the combined therapy compared with radiotherapy alone. In vivo studies demonstrated reduction of tumor vasculature and blood flow. In addition, 21 Gy in 7 fractions given concurrently with SU6668 resulted in tumor growth delay compared to either treatment alone.

CONCLUSION

These data suggest that the combination therapy was more effective in destroying tumor vasculature than either treatment alone. SU6668 augments tumor-suppressive effects of radiotherapy in Lewis lung carcinoma and GL261 xenographs, possibly through reducing the survival of tumor endothelium.

Radiotherapy patterns of care study in lung carcinoma

PURPOSE

For the first time, a lung Patterns of Care Study was conducted to determine the national patterns of radiation (RT) practice in patients treated for nonmetastatic lung cancer in 1998 to 1999.

MATERIALS AND METHODS

A national survey of randomly selected RT institutions in the United States was conducted using two-stage cluster sampling, stratified by practice type. Patients with nonmetastatic lung cancer (Karnofsky performance score [KPS] > or = 60), who received RT as definitive or adjuvant therapy, were randomly selected. To determine national estimates, sample size was weighted by the relative number of institutions per strata and the number of patient records reviewed per the number of patients eligible. Accordingly, 42,335 patient records from 58 institutions were reviewed by trained research associates. The unweighted sample size (or number of patients) was 541.

RESULTS

The histologies were small-cell lung cancer (SCLC) in 14.5% of patients versus non-small-cell lung cancer (NSCLC) in 85.5% of patients. The median age was 67 years (range, 29 to 92 years); 61% of patients were male, and 38% were current smokers. Bone scans and brain imaging were not obtained in 34% and 52% of clinical stage (CS) III NSCLC patients, respectively. Regarding treatment strategies, for SCLC and CS III NSCLC, chemotherapy plus RT was used significantly more than RT alone (P <.05); in CS I NSCLC, RT alone was the primary treatment (P <.05). Overall, 58% of patients received systemic therapy. On multivariate analysis, factors correlating with increased use of chemotherapy included younger age, histology (SCLC > NSCLC), increasing CS, increasing KPS, and lack of comorbidities. Only 3% of all patients were treated on prospective clinical trials.

CONCLUSION

This study establishes the general patterns of care for lung carcinoma in RT facilities within the United States. As supported by clinical trials, patients with limited-stage SCLC and CS III NSCLC received chemotherapy plus RT more than they received RT alone. Further improvements in staging, smoking cessation, and increased accrual to clinical trials must be encouraged.

The antiangiogenic agent SU5416 down-regulates phorbol ester-mediated induction of cyclooxygenase 2 expression by inhibiting nicotinamide adenine dinucleotide phosphate oxidase activity

Increased expression of cyclooxygenase (COX) 2 and the production of PGs appear to provide a survival advantage to transformed cells through the inhibition of apoptosis, increased attachment to extracellular matrix, increased invasiveness and the stimulation of angiogenesis. The purpose of this study was to determine whether an angiogenic antagonist, SU5416, could inhibit endogenous and phorbol 12-myristate 13-acetate (PMA)-mediated induction of COX-2 expression. SU5416 (5 micro M) inhibited endogenous as well as PMA-mediated induction of COX-2 expression when analyzed by immunoblot and Northern blot analysis. However, COX-1 expression remained unchanged under similar conditions. PMA is a potent inducer of reactive oxygen species that can play an important role during the induction of COX-2 expression. Our results demonstrated that PMA-mediated induction of COX-2 expression was found to be dependent on NADPH oxidase activity. An inhibitor of NADPH oxidase (diphenyleneiodonium chloride) blocked the PMA-mediated induction of COX-2 expression. The oxidase complex exhibited a temporal pattern of activation after exposure to PMA in which maximum activation was observed at 30 min after the addition of PMA. Activation of NADPH oxidase was also inhibited by SU5416, whereas an inhibitor of epidermal growth factor receptor signaling was unable to prevent the PMA-mediated induction of NADPH oxidase activity. When we blocked the PMA-mediated production of reactive oxygen species by blocking NADPH oxidase with SU5416, COX-2 expression and PGE(2) synthesis were also inhibited. Our results suggest that inhibition of NADPH oxidase activity, blocking of COX-2 expression, and PGE(2) synthesis may represent novel targets for SU5416.

Enhancing radiotherapy with cyclooxygenase-2 enzyme inhibitors: a rational advance?

Results of preclinical studies suggesting that the efficacy of molecular therapies is enhanced when they are combined with radiation have generated a surge of clinical trials combining these modalities. We reviewed the literature to identify the rationale and experimental foundation supporting the use of cyclooxygenase-2 (COX-2) inhibitors with standard radiotherapy regimens in current clinical trials. Radiation affects the ability of cells to divide and proliferate and induces the expression of genes involved in signaling pathways that promote cell survival or trigger cell death. Future advances in radiotherapy will hinge on understanding mechanisms by which radiation-induced transcription of genes governs cell death and survival, the selective control of this process, and the optimal approaches to combining this knowledge with existing therapeutic modalities. COX-2 is expressed in all stages of cancer, and in several cancers its overexpression is associated with poor prognosis. Evidence from clinical and preclinical studies indicates that COX-2-derived prostaglandins participate in carcinogenesis, inflammation, immune response suppression, apoptosis inhibition, angiogenesis, and tumor cell invasion and metastasis. Clinical trial results have demonstrated that selective inhibition of COX-2 can alter the development and the progression of cancer. In animal models, selective inhibition of COX-2 activity is associated with the enhanced radiation sensitivity of tumors without appreciably increasing the effects of radiation on normal tissue, and preclinical evidence suggests that the principal mechanism of radiation potentiation through selective COX-2 inhibition is the direct increase in cellular radiation sensitivity and the direct inhibition of tumor neovascularization. Results of current early-phase studies of non-small-cell lung, esophageal, cervical, and brain cancers will determine whether therapies that combine COX-2 inhibitors and radiation will enter randomized clinical trials.

Combined Modality Therapy for Locally Advanced Non-Small Cell Lung Cancer

The majority of non-small cell lung cancer patients present with locally advanced disease that may not be resectable. A single modality treatment such as thoracic radiotherapy often results in an inferior outcome when compared to combined modality treatment. Various combinations of radiotherapy, chemotherapy, and surgery have been tested in patients with locally advanced non-small-celllung cancer with promising results. The favorable results of the combined modality treatment are accompanied by a corresponding increase in treatment related morbidity. In this article, the results of the application of combined modality treatments in the management of locally advanced non-small cell lung cancer are reviewed.

Potential radiation-sensitizing effect of semisynthetic epothilone B in human lung cancer cells

BACKGROUND AND PURPOSE

To evaluate a semisynthetic epothilone B, BMS-247550, as a potential radiosensitizer in vitro and in vivo.

MATERIALS AND METHODS

Human NCI-H460 lung cancer cells were treated with either BMS-247550 or paclitaxel and in combination with radiation at multiple doses for different time periods. Surviving fractions were then analyzed using a clonogenic assay. Cell cycle redistribution by BMS-247550 was measured with propidium iodide and flow cytometry. Percent apoptosis was also measured using 7-amino-actinomycin D staining with flow cytometry. For in vivo studies, the H460 xenograft model was used in athymic nude mice. Tumors were treated with BMS-247550 (5 mg/kg) i.p. injection on days 0, 2, and 4 and/or radiation (2 Gy/day, days 0-4).

RESULTS

The in vitro radiation dose enhancement ratios (DER) of 1-h BMS-247550 and paclitaxel were 2.03 and 1.34, respectively. Treatment with BMS-247550 enhanced the G2/M block and induced apoptosis; whereas in combination with radiation, the induction of apoptosis was additive. BMS-247550 in combination with radiation in vivo enhanced the tumor growth delay when compared with either drug or radiation alone.

CONCLUSIONS

These results demonstrated that BMS-247550 could enhance the effects of radiation in human lung cancer cells both in vitro and in vivo and that a G2/M block and increased apoptosis might be possible explanations for the enhancement.

Potential for combined modality therapy of cyclooxygenase inhibitors and radiation

In conclusion, COX-2 inhibitors have potent anti-tumorigenic activity. Results from animal studies strongly indicate that the likely mechanism for enhanced TGD and TCD50 in tumors treated with radiation and COX-2 inhibitors was the inhibition of angiogenesis. In our recent findings we observed that the antagonists of angiogenesis also inhibited the endogenous as well as phorbol-ester-mediated induction of COX-2 expression in human lung cancer cell lines and that in the xenograft model a combination of angiogenic antagonists and radiation significantly delayed tumor growth [ASCO 2002, Vol. 21 (Part 1); p445a, #1779]. In human tumor models, apoptosis was another mechanism of cell death. Furthermore, it was demonstrated that COX-2 inhibitors could change the intrinsic radiosensitivity of human cancer cells [41]. Therefore, inhibition of angiogenesis by COX-2 inhibitors may be the major mechanism for increased radiation effects in tumors. However, other mechanisms such as changes in tumor perfusion, apoptosis, and an increase in intrinsic radiation sensitivity must also be considered. Inhibitors of COX-2 in combination with radiation therapy may be an alternative strategy that can be tested in clinical trials. The combination of COX-2 inhibitors and radiation suggest a complementary strategy to target angiogenesis while potentially minimizing the impact on quality of life. Currently, the Radiation Therapy Oncology Group [www.rtog.org] is just one of the National Cancer Institute sponsored cooperative groups conducting clinical trials in cervix cancer, lung cancer and brain tumors, using inhibitors of COX-2 in combination with chemotherapy and radiation therapy. These clinical trials will help elucidate the role of this interesting class of agents in combination with cytotoxic therapy for the treatment of cancer.

Chemotherapy and irradiation interaction

The combination of chemotherapeutic drugs with radiation therapy has perhaps been one of the most promising strategies for current cancer radiotherapy practice, and has a strong biologic rationale. Concurrent chemoradiotherapy has been shown to improve survival and locoregional control of various cancers compared with radiotherapy alone. This article reviews the biologic rationale and principles fundamental to the use of chemoradiotherapy, and discusses mechanistic interactions between drugs and radiation, the knowledge of which is essential in developing optimal treatment strategies. Chemotherapeutic agents, particularly those shown to augment the radiation response of tumors, will be reviewed, and novel compounds and some of the exciting emerging strategies for chemoradiotherapy will be presented.

Targeted therapies for stage III non-small cell lung cancer: integration in the combined modality setting

Combined modality therapy represents current standard therapy for locoregionally advanced non-small cell lung cancer. In particular, concomitant chemoradiotherapy has emerged as the preferred approach. At the same time, efforts to increase locoregional and systemic antitumor activity are necessary to further improve long-term survival rates for these patients. In recent years, multiple cellular targets have emerged in the development of novel antitumor therapies. Several of these are of high relevance in the carcinogenesis of lung cancer including the epidermal growth factor receptor (EGFR), the ras signaling pathway, tumor angiogenesis, and cyclooxygenase-2 (COX-2) expression. Novel agents directed against these targets are currently under development with promising early results in non-small cell lung cancer when administered as single agents or in combination with chemotherapy in stage IV or recurrent disease. Similarly their use with concurrent radiation therapy is supported by preclinical models. Selected early clinical trials utilizing these agents in combination with radiotherapy or chemoradiotherapy are discussed.

COX-2 inhibitor as a radiation enhancer: new strategies for the treatment of lung cancer

Lung cancer is one of the most common causes of cancer-related mortality throughout the world, and the incidence continues to increase. Smoking is the number one cause of lung cancer. Emerging data have implicated cyclooxygenase-2 (COX-2) and prostanoid production in the pathogenesis of lung carcinoma. In invasive lung tumors, COX-2 upregulation has been reported in up to 90% of cases. COX-2 upregulation is an early event in the development of non-small-cell lung cancer and may be integral to the development of new blood vessels and production of specific proteases that are critical to growth and spread of lung malignancies. COX-2 inhibitors are known to enhance the chemosensitivity in COX-2 overexpressing lung cancer cell lines. Recently, we have demonstrated that selective COX-2 inhibitors also enhance the effect of radiation in COX-2 overexpressed cells. Therefore, inhibitors of COX-2 in combination with chemoradiation therapy may be an alternative strategy that can be tested in clinical trials. The combination of COX-2 inhibitors and radiation suggest a complementary strategy to target angiogenesis while potentially minimizing the impact on quality of life. Currently, several groups are conducting clinical trials in cervix cancer, lung cancer, and brain tumors, using inhibitors of COX-2 in combination with chemotherapy and radiation therapy. These clinical trials will help to elucidate the role of this interesting class.

Concurrent chemoradiotherapy for inoperable stage III non-small-cell lung cancer

Chemoradiotherapy has become the standard treatment for patients with locally advanced non-small-cell lung cancer on the basis of several large randomized trials. Despite an increase in median survival from 10 months with radiotherapy alone to 16 to 17 months with concurrent chemoradiotherapy, long-term survival in this disease remains modest at best. With the advent of new biologic agents targeting specific cellular pathways associated with malignant progression, combined-modality therapy has the potential to target tumors selectively with less toxicity.

Adjuvant and neoadjuvant treatments for NSCLC

In stage III non-small cell lung cancer (NSCLC), the use of induction chemotherapy prior to radiotherapy produces a significant increase in median survival of three to four months (from 11 to 14 months), a benefit which appears to be achieved through improved systemic control of the disease. Hyperfractionated radiotherapy, although it enhances local control, seems not to improve survival. Concurrent chemoradiotherapy has emerged as the most successful strategy. It led to increased locoregional control and to a 3-4 month improvement of median survival when compared with induction chemotherapy prior to radiotherapy. Docetaxel is a radiosensitizing agent and has been extensively investigated in phase I/II settings of concurrent chemoradiotherapy. Use of the other cytotoxics such as paclitaxel, or irinotecan in concurrent chemoradiotherapy strategies is also feasible. Of particular interest are the results of SWOG 9504, a phase II study in which cisplatin/etoposide concurrent chemoradiotherapy was followed by three cycles of docetaxel consolidation. Median survival is 26 months, 1-year survival 76% and 3-year survival 40%. These survival data, achieved in pathologically staged IIIB patients, are highly encouraging and support further evaluation of this approach. Among stage III patients eligible for radical treatment with surgery or radiotherapy, the addition of neoadjuvant docetaxel at 100 mg/m(2) for three cycles is tolerable and appears to be associated with a trend towards increased survival.

Irinotecan in combination with radiation therapy for small-cell and non-small-cell lung cancer

Lung cancer is the leading cause of cancer-related death in the United States. There was rapidprogress in the treatment of lung cancer duringpast decades, but local control and survival rates are still poor. Radiation therapy has been an indispensable part of the management of lung cancer, and a recent paradigm is concurrent chemoradiation therapy. Many novel chemotherapeutic agents were recently developed to improve both local and systemic control of cancer, including camptothecin derivatives, which are topoisomerase I inhibitors. Irinotecan (CPT-11, Camptosar) is a semisynthetic water-soluble derivative of camptothecin. Irinotecan is active as a single agent against lung cancer, and is also a potent radiosensitizing agent in human lung cancer cell lines and xenografts. There have been many phase I and II clinical trials demonstrating promising results of single-agent irinotecan and combination with concurrent therapy. This article reviews irinotecan's mechanism of action of cytotoxicity and of radiation-sensitizing effects, as well as recent clinical data regarding combining radiation therapy and irinotecan for both non-small-cell and small-cell lung cancer.

Standards of care for anemia management in oncology: focus on lung carcinoma

BACKGROUND

Anemia is common in patients with lung carcinoma, particularly among those undergoing platinum-based cytotoxic chemotherapy. Evidence is growing that anemia can have a profound impact on the patient's quality of life, often manifested as the patient's inability to function normally.

METHODS

A literature review was conducted to provide a current picture of the incidence and impact of anemia in patients with lung carcinoma and the usage and limitations of current treatment.

RESULTS

The incidence of anemia (a hemoglobin [Hb] level < 11g/dL) in lung carcinoma patients is approximately 50-60%, varying according to treatment regimen. However, despite evidence supporting the treatment of anemia, many clinicians only intervene when Hb levels fall below 8 g/dL. This may be because of a lack of awareness of the incidence and impact of anemia on cancer patients, but most likely is because of limitations of current treatment options (blood transfusion and recombinant human erythropoietin [epoetin-alpha]). Darbepoetin-alpha represents a new generation of erythropoiesis-stimulating proteins. Biochemically distinct from epoetin-alpha, darbepoetin-alpha has a greater sialic acid content and biologic half-life than epoetin-alpha, but stimulates erythropoiesis in the same manner. Clinical trials involving patients with cancer-related anemia have shown that darbepoetin-alpha has a threefold longer half-life than epoetin-alpha, which may allow less frequent dosing. The results from an ongoing clinical trial dedicated to testing the clinical benefits of darbepoetin-alpha in treating anemia in lung carcinoma patients will provide a valuable insight into its full potential in this setting.

CONCLUSIONS

Anemia is common but is reported to be undertreated in patients with lung carcinoma. The introduction of darbepoetin-alpha into clinical practice may overcome some of the limitations of current treatments and facilitate improvement in the management of cancer-related anemia.

Declining hemoglobin during chemoradiotherapy for locally advanced non-small cell lung cancer is significant

BACKGROUND AND PURPOSE

Tumor hypoxia and anemia have been linked to poor overall survival and local control in carcinomas of both the uterine cervix and the head and neck for patients undergoing radiotherapy. Little is known about the effect of these factors on the outcome of NSCLC patients with locally advanced disease undergoing chemoradiation therapy.

MATERIALS AND METHODS

To examine the impact of anemia in stage III NSCLC patients undergoing combined modality therapy, we reviewed our database from three sequential trials of concurrent weekly paclitaxel +/- carboplatin and radiation therapy. 115 pts from 17 institutions were enrolled from 4/94 to 5/97. In this series, hemoglobin values were collected before treatment and weekly during radiotherapy. We correlated baseline Hb and Hb changes during chemoradiation treatment with overall survival.

RESULTS

Although pretreatment anemia was common (30% Hb = 110-130 g/l, 16% Hb <110 g/l), log-rank analyses of presenting Hb, average Hb and minimum Hb during treatment were not statistically significantly predictive of survival. However in a Cox model, declining hemoglobin during chemoradiation had a statistically significant impact on survival.

CONCLUSIONS

These analyses reveal that a decline in hemoglobin during chemoradiation for stage III NSCLC has a statistically significant correlation with overall survival. Strategies maximizing hemoglobin during combined modality therapy need further exploration in well-planned randomized trials.

Vascular endothelial growth factor-mediated angiogenesis inhibition and postoperative wound healing in rats

BACKGROUND

Vascular endothelial growth factor (VEGF) is an angiogenic factor that acts by binding to specific high-affinity tyrosine kinase receptors. SU5416 is an antiangiogenic agent that acts as a potent and selective inhibitor of the VEGF Flk-1/KDR receptor tyrosine kinase. SU5416 has been shown to inhibit VEGF-dependent mitogenesis of human endothelial cells and to decrease the growth of xenografts of melanoma, lung carcinoma, ovarian carcinoma, and gliomas. The effect of pre- or perioperative use of this drug on angiogenesis and wound healing in the postoperative setting has not been shown. We sought to analyze the efficacy and safety with respect to functional dosing of SU5416 in the setting of wound healing. This represents an important step forward in the use of this and similar drugs in the perioperative setting of treatment for multiple types of cancers. The use of an inhibitor of VEGF receptors such as SU5416 is distinct and it is likely complementary to other agents in the treatment of such cancers.

METHODS

We injected 8-week-old male Sprague-Dawley rats with SU5416 (8 or 12 mg/kg) or dimethyl sulfoxide intraperitoneally, daily for 14 days. We then performed a right pulmonary lobectomy and 6-mm full-thickness punch biopsies of the back. Tissue perfusion measured via laser Doppler on Postoperative Day 2 was 1.65, 1.22, and 1.14 perfusion units (P < 0.0004) for control, 8 mg/kg, and 12 mg/kg groups, respectively.

RESULTS

We successfully treated a murine model with functional doses of the anti-VEGF drug SU5416 so as to achieve decreased vascularity and blood flow in postoperative wounds. There was no effect on gross wound healing or infection in either control or treatment groups. Also, no drug-related impairment of histologic healing or decrease in wound tensile strength was demonstrated at either 6 or 14 days.

CONCLUSION

Preoperative therapy with functional dosing of SU5416 does not appear to have any major effect on postoperative morbidity or mortality in rats. We additionally conclude that preoperative therapy with SU5416 should be investigated further with careful attention to wound integrity.

Radiation enhancement by the combined use of topoisomerase I inhibitors, RFS-2000 or CPT-11, and topoisomerase II inhibitor etoposide in human lung cancer cells

BACKGROUND AND PURPOSE

We have tested the camptothecin analogs, RFS-2000 or CPT-11, in combination with both etoposide and ionizing radiation in vitro to examine the radiation enhancing potential of topoisomerase I plus topoisomerase II (Topo I+Topo II) inhibition in human cancer cells.

MATERIALS AND METHODS

H460 human lung carcinoma cells were plated and treated with 10nM RFS-2000 or 4.5microM CPT-11 for 4h. Cells were then irradiated with various doses and treated with 1microM etoposide for 1.5h. Cell survival and sublethal damage recovery (SLDR) were determined by clonogenic assay. 7-aminoactinomycin D (7-AAD) staining and flow cytometry were used to analyze cell viability/apoptosis after combined treatment of drugs with radiation.

RESULTS

Survival experiments showed radiation dose enhancement ratios (DER) of 1.26, 1.34, and 1.63 for RFS-2000, etoposide, and RFS-2000 plus etoposide, respectively; the corresponding DER values were 1.30, 1.39, and 1.65 for CPT-11, etoposide, and CPT-11 plus etoposide. The analysis of cell viability/apoptosis using 7-AAD staining and flow cytometry showed an additive effect. Greater inhibition of SLDR was observed with RFS-2000 plus etoposide than with either agent separately, but CPT-11 plus etoposide showed a more modest effect upon SLDR.

CONCLUSIONS

These data show that the combination of Topo I inhibitors, RFS-2000 or CPT-11 plus Topo II inhibitor etoposide, is a more effective radiation enhancer than either agent alone in human lung cancer cells. The mechanism of radiation enhancement may involve inhibition of SLDR with RFS-2000 plus etoposide, but other mechanisms may be involved in the combined treatment including CPT-11.

Phase I trial of outpatient weekly docetaxel, carboplatin and concurrent thoracic radiation therapy for stage III unresectable non-small-cell lung cancer: a Vanderbilt cancer center affiliate network (VCCAN) trial

PURPOSE

Docetaxel, an active agent for non-small cell lung cancer (NSCLC), has demonstrated activity as a radiosensitizer in numerous pre-clinical studies. We conducted a phase I trial to determine the maximum-tolerated dose (MTD) and dose-limiting toxicities (DLT) of weekly Docetaxel, Carboplatin with concurrent thoracic radiation therapy (TRT) in patients with unresectable stage III NSCLC.

PATIENTS AND METHODS

In this phase I clinical trial, Docetaxel was administered weekly as a 1-h intravenous infusion for 6 weeks with a starting dose of 20 mg/m(2). Docetaxel doses were escalated by 10 mg/m(2) increments in successive cohorts of three patients. DLT was defined as grade >or=3 nonhematologic and hematologic toxicity according to RTOG toxicity criteria. Once the DLT of Docetaxel alone was reached, weekly Carboplatin (AUC 2) was added at a DLT-2 dose of Docetaxel (two dose levels below that of dose limiting toxicity). Docetaxel doses were again escalated at 10 mg/m(2) increments in successive cohorts of three new patients to define further DLT and MTD of Docetaxel/Carboplatin with TRT. TRT was administered to the primary tumor and regional lymph nodes (40 Gy) followed by a boost to the tumor (20 Gy).

RESULTS

Fifteen patients were entered onto this study with Docetaxel alone through three dose escalations (from 20 to 40 mg/m(2) weekly). The DLT of weekly Docetaxel/TRT was esophagitis and the MTD was 30 mg/m(2) per week for 6 weeks. Nine more patients were added with the Docetaxel/Carboplatin/TRT regimen. The DLT of weekly Docetaxel/Carboplatin with TRT was esophagitis and the MTD of Docetaxel was 20 mg/m(2) per week with weekly Carboplatin (AUC 2). There were 2 complete responses and 13 partial responses in 25 evaluable patients (RR 60%).

CONCLUSIONS

This combination regimen has activity with manageable toxicity in patients with stage III NSCLC. A phase II study is planned to define activity.

The novel taxane analogs, BMS-184476 and BMS-188797, potentiate the effects of radiation therapy in vitro and in vivo against human lung cancer cells

PURPOSE

To evaluate the novel taxane analogs, BMS-184476 and BMS-188797, as potential radiosensitizers in vitro and in vivo.

METHODS AND MATERIALS

Human H460 lung cancer cells were incubated with either paclitaxel or a taxane analog and irradiated at various times. Surviving fractions were then determined using a clonogenic assay. Three different schedules were used: (A) 1-h drug incubation with radiation at t = 8 h, (B) 1-h drug incubation with radiation at t = 24 h, (C) 24-h drug incubation with radiation immediately after. Cell cycle redistribution by taxanes alone was measured with propidium iodide and flow cytometry. Percent apoptosis was also measured using 7-aminoactinomycin D (7-AAD) staining with flow cytometry. For in vivo studies, H460 cell xenografts were used in nude mice. Tumors were grown s.c. on the flank and then treated with BMS-184476 (10 mg/kg i.p. injection, Days 0, 2, and 4) and/or radiation (2 Gy/day, Days 0-4). Tumor growth delay was then measured for each treatment group.

RESULTS

The mean in vitro radiation dose enhancement ratios of BMS-184476, BMS-188797, and paclitaxel were 1.76, 1.49, and 1.31 for Schedules A, B, and C, respectively. Isobologram analysis showed that BMS-184476 was synergistic with radiation using Schedule A. Treatment with taxanes caused an increase in the percentage of G2/M cells at the time of irradiation. The mean fold increases in the %G2/M above control values for all three drugs were 5.6, 2.5, and 1.7 for Schedules A, B, and C, respectively. The combined effects of taxanes plus radiation on the induction of apoptosis were additive for all three drugs. In vivo studies showed that BMS-184476 can enhance the effects of fractionated radiotherapy, with an average enhancement factor of 1.66 obtained from three independent experiments.

CONCLUSIONS

These results demonstrated that the novel taxane analogs, BMS-184476 and BMS-188797, can enhance the effects of radiation in human lung cancer cells both in vitro and in vivo. These data also support the hypothesis that a G2/M block is involved in the radiosensitization caused by the taxanes.

A selective cyclooxygenase-2 inhibitor, NS-398, enhances the effect of radiation in vitro and in vivo preferentially on the cells that express cyclooxygenase-2

It has been proposed that Cyclooxygenase (COX)-2 inhibitors may be able to enhance the effects of chemotherapeutic or radiation treatment; however, currently few studies have been reported that define the radiation-enhancing effect of COX-2 inhibitors. We conducted in vitro radiation survival experiments using rat intestinal epithelial cells which were stably transfected with COX-2 cDNA in the sense (RIE-S) and antisense (RIE-AS) orientations to investigate the potential radiosensitizing effect of the selective COX-2 inhibitor, NS-398. Apoptosis was measured using 7-aminoactinomycin-D with flow cytometry to investigate underlying mechanisms for the effect of NS-398 on radiosensitivity. The same experiments were repeated with NCI-H460 human lung cancer cells, which express COX-2 constitutively, and HCT-116 human colon cancer cells, which lack COX-2 expression. In vivo tumor growth delay assays were also performed with tumors formed by H460 and HCT-116 cells. No difference was observed in the intrinsic radiation sensitivity of RIE-S and RIE-AS cells exposed to radiation alone. However, 150-400 microM of NS-398 enhanced radiosensitivity in a concentration-dependent manner in RIE-S cells with dose enhancement ratios of 1.2-1.9 at a surviving fraction of 0.25. However, this effect was not shown in RIE-AS cells. NS-398 enhanced radiosensitivity in H460 cells with a dose enhancement ratio of 1.8 but protected HCT-116 cells from the effects of radiation. Radiation-induced apoptosis was enhanced by NS-398 in RIE-S and H460 cells but not in RIE-AS and HCT-116 cells. Additionally, this radiation-enhancing effect in RIE-S cells seemed to be attributable to some mechanisms other than the reversal of radioresistance induced by COX-2. NS-398 (36 mg/kg) enhanced the effect of radiation on H460 tumors in vivo by an enhancement factor of 2.5; however, it did not enhance the radiosensitivity of HCT-116 tumors (enhancement factor = 1.04). These in vitro and in vivo results suggest that selective COX-2 inhibitors enhance the effect of radiation on tumors that express COX-2 but not on COX-2-lacking tumors. This effect may be attributable to enhancement of radiation-induced apoptosis. Thus, selective COX-2 inhibitors may have potential as radiosensitizers for treatment of human cancers.

Enhancement of tumor oxygenation and radiation response by the allosteric effector of hemoglobin, RSR13

Prior studies using pO(2) microelectrodes have shown that RSR13, an allosteric modifier of hemoglobin, increases tissue oxygenation in vivo. Recently, measurements of tissue oxygenation have been performed by many investigators using blood oxygen level-dependent magnetic resonance imaging (BOLD MRI). In this study, we tested the hypothesis that the BOLD MRI signal ratio in tumors will change after administration of RSR13. NCI-H460 human lung carcinoma cells were used as a xenograft in athymic nude mice. Mice with 1-cm(3) tumors in the flank were anesthetized and mounted on the MRI apparatus, and various doses of RSR13 were administered intraperitoneally (i.p.). MR images were then acquired at 10-min intervals for up to 60 min after injection. The effect of RSR13 on tumor response was studied using the same mouse xenograft model with tumor growth delay measurements. RSR13 increased the MRI signal ratio [Intensity(t)/Intensity(t = 0)] in a dose-dependent manner, with maximum increases occurring 30 min after RSR13 was administered. An RSR13 dose of 200 mg/kg proved to be optimum. Since the MRI signal ratio has been shown previously to be linearly related to tissue oxygenation, the changes in the MRI signal ratio can be attributed to changes in tumor oxygen levels. Using a 200-mg/kg dose of RSR13, with a 10-Gy dose of radiation administered to tumors 30 min later, enhancement of radiation-induced tumor growth delay by RSR13 was observed (enhancement factor = 2.8). Thus our MRI results support and verify the previously reported RSR13-induced increase in tumor oxygenation obtained using pO(2) microelectrodes. Based upon these results and other previous studies, the mechanism of enhancement of the effect of radiation by RSR13 probably involves an increase in tumor oxygenation.

Induction chemotherapy increases perioperative complications in patients undergoing resection for non-small cell lung cancer

BACKGROUND

Neoadjuvant chemotherapy before resection is the standard of care for stage IIIA non-small cell lung cancer in many institutions. Further, neoadjuvant therapy is being studied in earlier stage lung cancer and may be applied more broadly in the future. There is little information about the effect of preoperative chemotherapy on the perioperative complications and mortality after lung resection.

METHODS

All patients undergoing anatomic resection after neoadjuvant chemotherapy by a single surgeon at a single institution were compared with patients undergoing similar resections without preoperative chemotherapy. Complications were analyzed as life-threatening (pneumonia, emergency surgery, transfer to the intensive care unit, or intubation), major (prolonging hospital stay but not necessarily dangerous), and minor. The incidence of life-threatening complications, major complications, reintubation, tracheostomy, and mortality were analyzed to determine whether neoadjuvant chemotherapy might have an effect on these complications. Mortality was defined as hospital mortality. Two-tailed Student's t test was used to analyze differences in means and chi2 to determine differences in proportions. Differences less than 0.05 were considered significant.

RESULTS

Thirty-four patients underwent resection after neoadjuvant chemotherapy, and 67 patients underwent resection without preoperative therapy. No differences between the two groups in age, pulmonary function, or comorbid diseases were found. The patients receiving chemotherapy did have a more advanced stage (2.52 versus 1.55, p < 0.0001). Striking increases were found in incidence of life-threatening complications (6.0% versus 26.5%, p = 0.0036), major complications (19.4% versus 47.1%, p = 0.0037), reintubation (3.0% versus 17.6%, p = 0.0093), and tracheostomy (0% versus 11.8%, p = 0.0042) in those patients who received preoperative chemotherapy. There was no hospital mortality. However, 2 (neoadjuvant) patients died within 90 days after discharge from the hospital of pneumonia and pulmonary embolus. This difference was also significant (0% versus 5.89%, p = 0.045).

CONCLUSIONS

Neoadjuvant carboplatin and Taxol increased the perioperative life-threatening complications in this cohort of patients compared with a similar cohort undergoing operations by the same surgeon in the same institution. The most common life-threatening complication in patients receiving induction chemotherapy was the failure to respond to antibiotics given for pneumonia. Strategies to prevent these complications will be important, especially if chemotherapy before resection becomes the standard for earlier stages of non-small cell lung cancer.

The current state of paclitaxel and radiation in the combined-modality therapy of non-small cell lung cancer

The results of randomized trials have prompted an evolution in the treatment approach to inoperable locally advanced non-small cell lung cancer, from radiotherapy alone to sequential chemoradiotherapy and now to concurrent chemoradiotherapy. The improvement in outcome seen with a concurrent chemoradiotherapy approach may be because of spatial cooperation, enhanced radiosensitization, and/or enhanced cytotoxicity. The taxanes, specifically paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), delivered in combination with radiation have been extensively examined in both preclinical and clinical studies. Several mechanisms have been suggested to explain the enhanced tumor cell kill seen with paclitaxel and radiation, and phase II studies have examined this combination in the setting of inoperable stage III non-small cell lung cancer. This review will explore some of the studies with this treatment approach in locally advanced disease. We also will briefly discuss some of the ongoing trials that are attempting to refine the delivery of concurrent thoracic radiation and paclitaxel-based chemotherapy.

Irinotecan and radiation in combined-modality therapy for solid tumors

Irinotecan (CPT-11, Camptosar) is a camptothecin derivative that is thought to exert its cytotoxic effects by targeting topoisomerase I. It is believed that irinotecan stabilizes a DNA-topoisomerase I cleavable complex, and that interactions between this complex and the replication machinery may lead to cell death. There is a significant volume of in vitro and in vivo data demonstrating that irinotecan acts as a radiosensitizer. The exact mechanism of this radiosensitization is currently unknown. The increasing amount of data demonstrating improved outcomes with concurrent chemoradiation treatment of malignancies like lung cancer and head and neck cancer provide impetus for pursuing the addition of other drugs as radiosensitizers to improve local control further. Irinotecan is undergoing early clinical trials in the combined-modality setting in several disease sites. This article will provide an overview of the current status of irinotecan used concurrently with radiotherapy in the treatment of a variety of solid tumors.

Role of taxanes in the combined modality treatment of patients with locally advanced non-small cell lung cancer

The plant-derived taxanes have a unique mechanism of cytotoxic action and have shown interesting response and survival data in metastatic non-small cell lung cancer (NSCLC). Based on these results, taxane-based regimens have been investigated in combination with radiotherapy in unresectable NSCLC. Trials with paclitaxel-based concurrent chemoradiotherapy have shown 50-100% tumour response rates, 12-26 month median survivals and 32-52% 2-year survival rates. Trials with concurrent chemoradiotherapy with docetaxel have shown 35-92% tumour response rates, 12-23 month median survivals, and 41-43% 2 year survival rates. Taxane-based concurrent chemoradiotherapy for stage III NSCLC appears promising. Large ongoing randomised trials will define the role of these agents in the treatment of locally advanced NSCLC.