Role of Cyclooxygenase-2 Inhibitors in Combination with Radiation Therapy in Lung Cancer

Phase I clinical trial of nasopharyngeal radiotherapy and concurrent celecoxib for patients with locoregionally advanced nasopharyngeal carcinoma

We evaluated the incidence of acute toxicity of concurrent cyclooxygenase-2 inhibitor (celecoxib) plus radiotherapy in patients with locoregionally advanced nasopharyngeal carcinoma (NPC). Thirty-four patients received an accumulated radiation dose of 72-76Gy in 36-38 fractions to the primary lesion and 60Gy in 30 fractions to cervical lymph-node lesions. Palpable residual nodes were boosted to 70Gy at the 90% isodose level with an electron field. Celecoxib was administered at escalating doses of 400, 600, and 800mg/day, starting 3days before the first fraction of radiotherapy and continuing throughout the course of radiotherapy. The majority of toxicities were grade 1, with mucositis and weight loss most frequently observed (28 of 34, 82.4%), followed by dermatitis (27 of 34, 79.4%) and otitis (14 of 34, 41.2%). The toxicities were not related to celecoxib dose (all P>0.05). Stomach pain was considered related to celecoxib, which developed in 2 patients at doses of 400mg and 800mg/day. No grade-3 or -4 toxicities or episodes of toxic death occurred. The tumors in 31 patients (31/34, 91.2%) showed a complete response, and 3 patients (3/34, 8.8%) had partial responses. The actuarial local progression-free survival was 96.6% at 1year, and the 2year overall survival rate was 84.6%. Celecoxib can be safely administered concurrently with nasopharyngeal radiotherapy at doses up to 800mg/day. The tumors responded well to treatment warranting further assessment in a phase II trial.

Effects of propranolol in combination with radiation on apoptosis and survival of gastric cancer cells in vitro

Background

The National Comprehensive Cancer Network (NCCN) guidelines recommend radiotherapy as a standard treatment for patients with a high risk of recurrence in gastric cancer. Because gastric cancer demonstrates limited sensitivity to radiotherapy, a radiosensitizer might therefore be useful to enhance the radiosensitivity of patients with advanced gastric carcinoma. In this study, we evaluated if propranolol, a β-adrenoceptor (β-AR) antagonist, could enhance radiosensitivity and explored its precise molecular mechanism in gastric cancer cells.

Methods

Human gastric adenocarcinoma cell lines (SGC-7901 and BGC-823) were treated with or without propranolol and exposed to radiation. Cell viability and clonogenic survival assays were performed, and cell apoptosis was evaluated with flow cytometry. In addition, the expression of nuclear factor κB (NF-κB), vascular endothelial growth factor (VEGF), cyclooxygenase 2 (COX-2), and epidermal growth factor receptor (EGFR) were detected by western blot and real-time reverse transcription polymerase chain reaction (PCR).

Results

Propranolol combined with radiation decreased cell viability and clonogenic survivability. Furthermore, it also induced apoptosis in both cell lines tested, as determined by Annexin V staining. In addition, treatment with propranolol decreased the level of NF-κB and, subsequently, down-regulated VEGF, COX-2, and EGFR expression.

Conclusions

Taken together, these results suggested that propranolol enhanced the sensitivity of gastric cancer cells to radiation through the inhibition of β-ARs and the downstream NF-κB-VEGF/EGFR/COX-2 pathway.

Radiation sensitivity of human carcinoma cells transfected with small interfering RNA targeted against cyclooxygenase-2

PURPOSE

Cyclooxygenase-2 (COX-2) is considered a potential target for cancer therapy, because COX-2 levels are elevated in the majority of human tumors compared with the normal tissues. COX-2 inhibitors inhibit tumor growth and enhance radiation response in vitro as well as in vivo. However, the precise role of COX-2 in radiation response is not clear. The purpose of the present study was to investigate the in vitro radiosensitivity of tumor cells as a function of COX-2 expression.

EXPERIMENTAL DESIGN AND RESULTS

PC3 and HeLa cells express COX-2 protein constitutively. We silenced the COX-2 gene in these cells using small interfering RNA (siRNA). Transfection of PC3 cells with 100 nmol/L siRNA targeted against COX-2 resulted in reduction of COX-2 protein by 75% and inhibition of arachidonic acid-induced prostaglandin E2 synthesis by approximately 50% compared with the vehicle control. In HeLa cells, 100 nmol/L COX-2 siRNA inhibited COX-2 protein expression by 80%. Cell cycle analysis showed that transfection with COX-2 siRNA did not alter the cell cycle distribution. Radiosensitivity was determined by clonogenic cell survival assay. There was no significant difference in the radiosensitivity of cells in which COX-2 was silenced compared with the cells transfected vehicle or with negative control siRNAs (enhancement ratio = 1.1).

CONCLUSIONS

These data indicate that the in vitro radiosensitivity of tumor cells is minimally dependent on the cellular COX-2 status. Given that a number of potential mechanisms are attributed to COX-2 inhibitors for radiosensitization, specific intervention of COX-2 by RNA interference could help elucidate the precise role of COX-2 in cancer therapy and to optimize strategies for COX-2 inhibition.

COX-2 inhibitors suppress lung cancer cell growth by inducing p21 via COX-2 independent signals

COX-2 has been implicated in the control of human non-small cell lung carcinoma (NSCLC) cell growth. The mechanisms by which COX-2 exerts its mitogenic effects have not been entirely elucidated, but stimulation of prostaglandin E2 production and alterations in the expression of the cyclin-dependent kinase inhibitor p21(WAF-1/CIP1/MDA-6)(p2i) have been suggested. Here, we demonstrate that two COX-2 inhibitors (NS398 and Nimesulide) inhibit proliferation and induce apoptosis in NSCLC cells, and these effects were associated with induction of p21 mRNA and protein expression. However, the anti-growth effect of the COX-2 inhibitors and their ability to induce p21 were not affected by COX-2 siRNA suggesting that their actions were COX-2 independent. Instead, activation of the MEK-1/Erk pathway was necessary since COX-2 inhibitors stimulated the phosphorylation of ERKs, and their effects were blocked by PD98095, an inhibitor of this pathway. Furthermore, we show that both NS398 and Nimesulide induced p21 gene promoter activity and this was prevented by PD98095. COX-2 inhibitors increased nuclear protein binding to the Spl site in the promoter region of the p21 gene. Consistent with a role for p21, we found that p21 antisense oligonucleotides prevented the effects of COX-2 inhibitors on cell growth. In summary, our results suggest that COX-2 inhibitors suppress NSCLC cell growth by inducing the expression of the p21 gene through MEK-1/ERK signaling and DNA-protein interactions involving Spl. These observations unveil a mechanism for p21 gene regulation by COX-2 inhibitors in lung carcinoma cell growth and this pathway represents a potential target for therapy.

Chemoprevention Strategies for Patients with Lung Cancer in the Context of Screening

Despite major advances in the treatment and management of lung cancer, most patients with lung cancer eventually die of this disease. Because conventional therapies have failed to make a major impact on survival, newer approaches are necessary in the battle against lung cancer. Better understanding of molecular biology of several tumors has led to novel targeted therapeutic approaches with potential utility in cancer treatment in general and lung cancer in particular. In addition to smoking cessation, targeting individuals at high risk by use of early detection or aiming at reversal of premalignant lesions seem like attractive strategies. In light of the noted improvement in molecular diagnostic tools and targeted therapies, the question of chemoprevention in the context of early detection deserves a closer look. In this article, we review what has been achieved in the area of chemoprevention and discuss possible prospects that may help reduce lung cancer mortality in the context of early detection.

COX-2 inhibitors suppress integrin alpha5 expression in human lung carcinoma cells through activation of Erk: involvement of Sp1 and AP-1 sites

Tumor cell expression of COX-2 has been implicated in the progression of murine and human lung cancer. Inhibition of COX-2 by nonsteroidal antiinflammatory drugs reduces the risk of cancer development in humans and suppresses tumor growth in animal models. However, the underlying mechanisms for this beneficial effect are not fully understood. Here we explore the potential link between the anticancer effects of COX-2 inhibitors and the expression of the integrin alpha5beta1. Expression of this integrin in carcinoma cells is associated with invasiveness and malignant progression. This, together with our studies showing that fibronectin, the ligand of alpha5beta1, stimulates the growth of human lung carcinoma cells, and that this effect is mediated through alpha5beta1-dependent signals, has prompted us to examine the effects of COX-2 inhibitors on alpha5beta1 expression in human non small cell lung carcinoma (NSCLC) cells. We found that the selective COX-2 inhibitors NS398 and Nimesulide decreased mRNA expression and protein production of the integrin alpha5 subunit. This effect was associated with inhibition of NSCLC cell adhesion to fibronectin. The COX-2 inhibitors triggered the phosphorylation of extracellular signal-regulated kinase (Erk) in a time-dependent manner, and the inhibitor of Mek-1/Erk PD98095 prevented their inhibitory effects on integrin alpha5 expression. Transient transfection assays showed that the COX-2 inhibitors affected integrin alpha5 gene transcription by acting between -92 to -41 bp of the human integrin alpha5 gene promoter. Gel mobility shift assays showed that the COX-2 inhibitors increased Sp1 DNA binding, but decreased that of AP-1. These effects were accompanied by an increase in Sp1 protein and a decrease in c-Jun protein expression, as well as inhibition of SAPK/JNK phosphorylation. The Sp1 inhibitor, Mithramycin A, also blocked the inhibitory effect of the COX-2 inhibitors on alpha5 expression and promoter activity. Overall, these findings suggest that COX-2 inhibitors suppress alpha5beta1 integrin expression in NSCLC through effects on integrin alpha5 gene transcription mediated by Erk activation, increased Sp1, decreased AP-1 DNA binding and inactivation of SAPK/JNK signals. Our observations unveil a new mechanism of action against NSCLC for COX-2 inhibitors that relates to regulation of integrin alpha5 gene expression and, consequently, recognition of extracellular matrices (i.e., fibronectin) by tumor cells. (c) 2005 Wiley-Liss, Inc.

A phase I clinical trial of thoracic radiotherapy and concurrent celecoxib for patients with unfavorable performance status inoperable/unresectable non-small cell lung cancer

OBJECTIVES

Preclinical observations that selective cyclooxygenase-2 inhibitors enhance in vitro cell radiosensitivity and in vivo tumor radioresponse led to clinical trials testing therapeutic efficacy of these agents. Our study was designed to determine whether the COX-2 inhibitor celecoxib could be safely administered in doses within those approved by the Food and Drug Administration when used concurrently with thoracic radiotherapy in patients with poor prognosis non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

The trial consisted of three cohorts of patients: (a) locally advanced NSCLC with obstructive pneumonia, hemoptysis, and/or minimal metastatic disease treated with 45 Gy in 15 fractions; (b) medically inoperable early-stage NSCLC treated with definitive radiation of 66 Gy in 33 fractions; and (c) patients who received induction chemotherapy but who were not eligible for concurrent chemoradiotherapy trials. These patients received 63 Gy in 35 fractions. Celecoxib was administered p.o. on a daily basis 5 days before and throughout the course of radiotherapy. Celecoxib doses were escalated from 200, 400, 600, to 800 mg/d given in two equally divided doses. Two to eight patients of each cohort were assigned to each dose level of celecoxib.

RESULTS

Forty-seven patients were enrolled in this protocol (19 in cohort I, 22 in cohort II, and 6 in cohort III). The main toxicities were grades 1 and 2 nausea and esophagitis, and they were independent of the dose of celecoxib or radiotherapy schedule. Only two patients in group II developed grade 3 pneumonitis 1 month after treatment, one on 200 mg, and the other on 400 mg celecoxib. Celecoxib-related toxicity developed in 3 of 47 patients: an uncontrolled hypertension in one patient on 800 mg celecoxib and hemorrhagic episodes in 2 patients (shoulder hematoma in one and hemoptysis in the other) on 200 mg celecoxib who were on warfarin for other medical reasons. Of 37 patients evaluable for tumor response, 14 had complete response, 13 partial responses, and 10 stable or progressive disease. The actuarial local progression-free survival was 66.0% at 1 year and 42.2% at 2 years following initiation of radiotherapy.

CONCLUSIONS

These results show that celecoxib can be safely administered concurrently with thoracic radiotherapy when given up to the highest Food and Drug Administration-approved dose of 800 mg/d, which we used. A maximal tolerated dose was not reached in this study. The treatment resulted in actuarial local progression-free survival of 66.0% at 1 year and 42.2% at 2 years, an encouraging outcome that warrants further assessment in a phase II/III trial.

Novel targeted agents in the treatment of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the US. Although an improvement in outcome is possible with the continued advancement of cytotoxic-based treatment, clinical research is currently focused on utilising novel molecular targets with proven efficacy in preclinical models and a low toxicity profile. This is the result of advances in understanding of tumour biology and molecular pathways that have been implicated in cancer pathogenesis and progression. Novel agents targeting cell cycle regulation, angiogenesis and signal transduction pathways have reached clinical testing in lung cancer and are discussed in this review.

Novel treatments in non–small cell lung cancer

Although it has been exciting for lung cancer doctors to observe objective remissions with gefitinib and erlotinib in heavily pretreated NSCLC patients, all of the reported phase III trials testing noncytotoxic, targeted therapies in NSCLC have been negative. Two basic strategies have been employed in developing and conducting these randomized studies. In the case of gefitinib and the matrix metalloproteinase inhibitors, phase III trials were launched based on preclinical data. The second strategy was based on survival results from phase II trials involving regimens consisting of the targeted agent and chemotherapy. Unfortunately, negative results have been observed with the first phase III study (chemotherapy +/- ISIS 3521), which was based on the results of a phase II trial. The initial negative results with targeted agents suggest that a paradigm shift in cancer drug development is needed. Typically, the development of a cytotoxic agent involves determination of the maximum tolerated dose, followed by an assessment of activity as defined by the objective response rate in specific tumor types. "Active" drugs are then moved into phase III testing to determine the effect on survival. Other than targeting the specific tumor type and defining the usual eligibility parameters, no attempt is made to select patients for treatment with new agents. It seems unlikely that there will be significant progress with the targeted therapies unless there is a paradigm shift from this classic model of cancer drug development to a model in which much greater effort is directed toward identifying the target or targets in preclinical models. Intensive effort should be devoted to the development of reliable, clinically applicable assays for the targets that could identify patients who are most likely to benefit from a specific treatment. Rothenberg et al recently made similar recommendations with respect to improving the drug discovery process for cancer. These investigators have emphasized testing new agents in the most appropriate setting, increasing efforts to understand the role of the target, and collection of tissue in an effort to select appropriate patients. Although results from initial randomized trials of targeted therapies in NSCLC have been relatively disappointing, this is not a time to be discouraged. Rather, it is a time to increase the collaborative efforts between basic scientists and clinical investigators.