ZD1839 modulates paclitaxel response in renal cancer by blocking paclitaxel-induced activation of the epidermal growth factor receptor-extracellular signal-regulated kinase pathway

Circumventing Drug Resistance Pathways with a Nanoparticle-Based Photodynamic Method

Drug resistance remains the dominant impediment for cancer therapy, not only because compensatory drug resistance pathways are always activated, but also because of the cross-resistance of cancer cells to unrelated therapeutics. Herein, chemodrug-sensitive cancer cells, intrinsic drug-resistant cells, and acquired resistant cells were employed to uncover their biological response to a nanoparticle-based photodynamic method in tumoral, cellular, and molecular levels. We observed that nanoparticle-based photodynamic process with high therapeutic efficiency, intracellular delivery, and tumor penetration effect resulted in the indiscriminate and significant therapeutic outcome, in contrast to the diversiform effect of first-line chemo-drug, Temozolomide (TMZ). By real-time quantitative PCR array technique, we revealed that signals in classical resistance pathways were unaffected or downregulated, and photodynamic effect initiates cell apoptosis via downstream genes. The discovery that nanoparticulate photodynamic therapy bypasses the signals in multiple resistant pathways may imply an alternative route for combating drug resistance of cancer.

MiR-145 in cancer therapy resistance and sensitivity: A comprehensive review

MircoRNA (miRNA) are a group of small, non–coding, regulatory RNA with an average length of approximately 22 nucleotides, which mostly modulate gene expression post–transcriptionally through complementary binding to the 3ʹ‐untranslated region (3ʹ‐UTR) of multiple target genes. Emerging evidence has shown that miRNA are frequently dysregulated in a variety of human malignancies. Among them, microRNA‐145 (miR‐145) has been increasingly identified as a critical suppressor of carcinogenesis and therapeutic resistance. Resistance to tumor therapy is a challenge in cancer treatment due to the daunting range of resistance mechanisms. We reviewed the status quo of recent advancements in the knowledge of the functional role of miR‐145 in therapeutic resistance and the tumor microenvironment. It may serve as an innovative biomarker for therapeutic response and cancer prognosis.

Cancer stem cells and chemoresistance: The smartest survives the raid

Chemoresistant metastatic relapse of minimal residual disease plays a significant role for poor prognosis of cancer. Growing evidence supports a critical role of cancer stem cell (CSC) behind the mechanisms for this deadly disease. This review briefly introduces the basics of the conventional chemotherapies, updates the CSC theories, highlights the molecular and cellular mechanisms by which CSC smartly designs and utilizes multiple lines of self-defense to avoid being killed by chemotherapy, and concisely summarizes recent progress in studies on CSC-targeted therapies in the end, with the hope to help guide future research toward developing more effective therapeutic strategies to eradicate tumor cells in the patients.

EGFR targeted therapies and radiation: Optimizing efficacy by appropriate drug scheduling and patient selection

The epidermal growth factor receptor (EGFR) plays an important role in tumor progression and treatment resistance for many types of malignancies including head and neck, colorectal, and nonsmall cell lung cancer. Several EGFR targeted therapies are efficacious as single agents or in combination with chemotherapy. Given the toxicity associated with chemoradiation and poor outcomes seen in several types of cancers, combinations of EGFR targeted agents with or without chemotherapy have been tested in patients receiving radiation. To date, the only FDA approved use of an anti-EGFR therapy in combination with radiation therapy is for locally advanced head and neck cancer. Given the important role EGFR plays in lung and colorectal cancer and the benefit of EGFR inhibition combined with chemotherapy in these disease sites, it is perplexing why EGFR targeted therapies in combination with radiation or chemoradiation have not been more successful. In this review we summarize the clinical findings of EGFR targeted therapies combined with radiation and chemoradiation regimens. We then discuss the interaction between EGFR and radiation including radiation induced EGFR signaling, the effect of EGFR on DNA damage repair, and potential mechanisms of radiosensitization. Finally, we examine the potential pitfalls with scheduling EGFR targeted therapies with chemoradiation and the use of predictive biomarkers to improve patient selection.

RLIP76 Targeted Therapy for Kidney Cancer

Despite recent improvements in chemotherapeutic approaches to treating kidney cancer, this malignancy remains deadly if not found and removed at an early stage of the disease. Kidney cancer is highly drug-resistant, which may at least partially result from high expression of transporter proteins in the cell membranes of kidney cells. Although these transporter proteins can contribute to drug-resistance, targeting proteins from the ATP-binding cassette transporter family has not been effective in reversing drug-resistance in kidney cancer. Recent studies have identified RLIP76 as a key stress-defense protein that protects normal cells from damage caused by stress conditions, including heat, ultra-violet light, X-irradiation, and oxidant/electrophilic toxic chemicals, and is crucial for protecting cancer cells from apoptosis. RLIP76 is the predominant glutathione-electrophile-conjugate (GS-E) transporter in cells, and inhibiting it with antibodies or through siRNA or antisense causes apoptosis in many cancer cell types. To date, blocking of RLIP76, either alone or in combination with chemotherapeutic drugs, as a therapeutic strategy for kidney cancer has not yet been evaluated in human clinical trials, although there is considerable potential for RLIP76 to be developed as a therapeutic agent for kidney cancer. In the present review, we discuss the mechanisms underlying apoptosis caused by RLIP76 depletion, the role of RLIP76 in clathrin-dependent endocytosis deficiency, and the feasibility of RLIP76-targeted therapy for kidney cancer.

Phase II trial of paclitaxel-carboplatin with intercalated gefitinib for untreated, epidermal growth factor receptor gene mutation status unknown non-small cell lung cancer

BACKGROUND

This study was conducted to evaluate the efficacy and safety of paclitaxel-carboplatin combined with intercalated gefitinib in patients with advanced, untreated, nonsquamous non-small cell lung cancer.

METHODS

A total of 29 patients were enrolled in the study. All patients were Chinese, with a histology type of adenocarcinoma, without a smoking history, and as a result of the limited tissue sample, an epidermal growth factor receptor (EGFR) mutation test could not be performed. All patients received chemotherapy of paclitaxel-carboplatin every 21 days for four cycles, and gefitinib (250 mg/day) was administered on days eight to 17 of the chemotherapy cycle. If the patient responded to chemotherapy, maintenance therapy of 250mg of gefitinib could be administered daily.

RESULTS

All of the 29 patients received at least one cycle of chemotherapy and gefitinib, and 25 patients received four cycles of therapy. Eighteen patients selected maintenance therapy with gefitinib. The objective response rate was 74.1% (95% confidence interval, 53.7% to 88.9%). No complete response was achieved. The median progression-free survival was 16 months, however, the median overall survival was not available by the conclusion of the study. The major adverse event was hematologic toxicity.

CONCLUSIONS

The regimen of paclitaxel-carboplatin combined with intercalated gefitinib showed a high response rate and a favorable safety profile. Gefitinib maintenance therapy was proven to be beneficial. This study proposes a good pattern of chemotherapy combined with EGFR tyrosine kinase inhibitors.

Cancer drug resistance: an evolving paradigm

Resistance to chemotherapy and molecularly targeted therapies is a major problem facing current cancer research. The mechanisms of resistance to 'classical' cytotoxic chemotherapeutics and to therapies that are designed to be selective for specific molecular targets share many features, such as alterations in the drug target, activation of prosurvival pathways and ineffective induction of cell death. With the increasing arsenal of anticancer agents, improving preclinical models and the advent of powerful high-throughput screening techniques, there are now unprecedented opportunities to understand and overcome drug resistance through the clinical assessment of rational therapeutic drug combinations and the use of predictive biomarkers to enable patient stratification.

Adenoviral neutral endopeptidase gene delivery in combination with paclitaxel for the treatment of prostate cancer

Neutral endopeptidase (NEP) is a cell-surface peptidase that inhibits prostate cancer cell growth partly via inhibition of Akt kinase. We investigated the antitumor effects of an adenovirus gene delivery system (AdNEP) to restore NEP expression in DU145 prostate cancer cells in combination with paclitaxel chemotherapy. DU145 cells were infected with adenovirus expressing NEP or LacZ, treated with paclitaxel, and assessed for cell viability, Akt activation and induction of apoptosis. Athymic mice with established DU145 xenografts were injected intratumorally with AdNEP or AdLacZ and intraperitoneally with paclitaxel and monitored for tumor growth over 28 days. Compared to AdLacZ plus paclitaxel, AdNEP plus paclitaxel significantly inhibited DU145 cell growth and increased apoptosis as determined by increased caspase-3 and PARP-1 proteolytic fragments. In a xenograft model, tumor volume was reduced in mice treated with AdNEP plus paclitaxel (122.85±89.5 mm³; P<0.01) compared with mice treated with AdNEP plus saline (653.9±230.3 mm³), AdLacZ plus paclitaxel (575.9±176.6 mm³) or AdLacZ plus saline (920.2±238.2 mm³). In conclusion, these data suggest that NEP can augment taxane-induced apoptosis through inhibition of Akt/Bad signaling, and that the combination of NEP plus paclitaxel may be an effective strategy to inhibit castration-resistant prostate cancer growth.

Silibinin inhibits the invasion and migration of renal carcinoma 786-O cells in vitro, inhibits the growth of xenografts in vivo and enhances chemosensitivity to 5-fluorouracil and paclitaxel

Silibinin is a flavonoid antioxidant that is widely used for its anti-hepatotoxic properties. It exerts a dose-dependent inhibition on the invasion and migration of 786-O renal cell carcinoma (RCC) cells in the absence of cytotoxicity. 786-O cells were treated with silibinin at various concentrations, up to 50 µM, for a defined period and then subjected to gelatin zymography, casein zymography, and Western blot to investigate the impacts of silibinin on metalloproteinase (MMP) -2, -9, urokinase plasminogen activator (u-PA), and MAPK pathway signaling proteins, respectively. The results showed that silibinin decreased MMP-2, MMP-9, u-PA, p-p38, and p-Erk1/2 expressions in a concentration-dependent manner. The reduced expressions of MMP-2 and u-PA, as well as inhibition of cell invasion were obtained in the cultures pre-treated with PD98059 (Erk1/2 inhibitor) and SB203580 (p38 inhibitor). An in vivo anti-tumor study with a nude mice xenograft model by a subcutaneous inoculation of 786-O cells demonstrated small solid tumors after eight days following cell inoculation. There was a 70.1% reduction in tumor volume and 69.7% reduction in tumor weight by silibinin feeding on day 44, compared to those of controls. Moreover, combination treatment with silibinin and 5-fluorouracil, paclitaxel, vinblastine, or RAD-001 enhanced the chemosensitivity of 5-fluorouracil and paclitaxel. In conclusion, silibinin inhibits the invasion and migration of 786-O cells in vitro, inhibits the growth of xenografts in vivo, and enhances chemosensitivity to 5-fluorouracil and paclitaxel. © 2011 Wiley-Liss, Inc.

Phase II study of cetuximab in combination with chemoradiation in patients with stage IIIA/B non-small-cell lung cancer: RTOG 0324

PURPOSE

Non-small-cell lung cancer (NSCLC) commonly expresses the epidermal growth factor receptor (EGFR), which is associated with poor clinical outcome. Cetuximab is a chimerized monoclonal antibody that targets the EGFR and, in preclinical models, it demonstrates radiosensitization properties. We report a phase II trial testing the combination of cetuximab with chemoradiotherapy (CRT) in unresectable stage III NSCLC.

PATIENTS AND METHODS

Eligibility criteria included unresectable stage III NSCLC, Zubrod performance status ≤ 1, weight loss ≤ 5%, forced expiratory volume in 1 second ≥ 1.2 L, and adequate organ function. Patients received an initial dose of cetuximab (400 mg/m(2)) on day 1 of week 1 and then weekly doses of cetuximab (250 mg/m(2)) until completion of therapy (weeks 2 through 17). During week 2, patients started CRT (63 Gy in 35 fractions) with weekly carboplatin at area under the [concentration-time] curve (AUC) 2 and six doses of paclitaxel at 45 mg/m(2) followed by carboplatin (AUC 6) and two cycles of paclitaxel (200 mg/m(2)) during weeks 12 through 17. Primary end points included safety and compliance of concurrent cetuximab and CRT.

RESULTS

In all, 93 patients were enrolled and 87 were evaluable. Median follow-up was 21.6 months. Response rate was 62% (n = 54), median survival was 22.7 months, and 24-month overall survival was 49.3%. Adverse events related to treatment included 20% grade 4 hematologic toxicities, 8% grade 3 esophagitis, and 7% grade 3 to 4 pneumonitis. There were five grade 5 events.

CONCLUSION

The combination of cetuximab with CRT is feasible and shows promising activity. The median and overall survival achieved with this regimen were longer than any previously reported by the Radiation Therapy Oncology Group.

Cetuximab in combination therapy: from bench to clinic

Cetuximab, a chimeric IgG(1) monoclonal antibody directed against the ligand-binding domain of the epidermal growth factor receptor, offers a paradigm for the combination of molecularly targeted therapies with cytotoxic agents. In preclinical models, the addition of cetuximab to chemotherapy or radiation therapy enhances antitumor activity. Proposed mechanisms include reducing tumor cell proliferation, angiogenesis, and DNA repair capacity; increasing apoptosis; and inducing cell cycle arrest at treatment-sensitive points. These effects may enhance and restore tumor sensitivity to cytotoxic therapies. In clinical trials, the addition of cetuximab to chemotherapy improves outcomes of patients who had previously failed such agents, as illustrated in irinotecan-resistant and oxaliplatin-refractory metastatic colorectal cancer. As initial therapy, the addition of cetuximab to chemotherapy extends survival in colorectal cancer, lung cancer, and head and neck cancer. Combining cetuximab with radiation therapy extends survival in locally advanced head and neck cancer. As predictive biomarkers are identified, it may become possible to select patients most likely to benefit from such combinations.

Targeted inhibition of the EGFR pathways enhances Zn-BC-AM PDT-induced apoptosis in well-differentiated nasopharyngeal carcinoma cells

Epidermal growth factor receptor (EGFR), a receptor often expressed in nasopharyngeal carcinoma (NPC) cells, is one of the recently identified molecular targets in cancer treatment. In the present study, the effects of combined treatment of Zn-BC-AM PDT with an EGFR inhibitor AG1478 were investigated. Well-differentiated NPC HK-1 cells were subjected to PDT with 1 microM of Zn-BC-AM and were irradiated at a light dose of 1 J/cm(2) in the presence or absence of EGFR inhibitor AG1478. Specific protein kinase inhibitors of downstream EGFR targets were also used in the investigation. EGFR, Akt, and ERK were found constitutively activated in HK-1 cells and the activities could be inhibited by the EGFR inhibitor AG1478. A sub-lethal concentration of AG1478 was found to further enhance the irreversible cell damage induced by Zn-BC-AM PDT in HK-1 cells. Pre-incubation of the cells with specific inhibitors of EGFR (AG1478), PI3k/Akt (LY294002), or MEK/ERK (PD98059) before light irradiation were found to enhance Zn-BC-AM PDT-induced formation of apoptotic cells. The efficacy of Zn-BC-AM PDT can be increased through the inhibition of EGFR/PI3K/Akt and EGFR/MEK/ERK signaling pathways in NPC cells. Combination therapy with Zn-BC-AM PDT and EGFR inhibitors may further be developed for the treatment of advanced NPC.

Phase II study of paclitaxel and irinotecan with intercalated gefitinib in patients with advanced non-small-cell lung cancer

OBJECTIVES

We conducted a phase II study of combination chemotherapy with paclitaxel (Pac) and irinotecan (CPT) alternating with gefitinib (Gef) to determine the qualitative and quantitative toxicities and efficacy of this combination against advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with stage IIIB or IV NSCLC were treated with CPT at 60 mg/m2 and Pac at 160 mg/m2 on day 1 followed by Gef at 250 mg per day on days 8 to 14 every 3 weeks.

RESULTS

Between April 2005 and March 2006, 16 patients received the chemotherapy with Pac and CPT alternating with Gef. Eleven patients received 4 to 6 cycles, except for 5 patients who discontinued treatment in the second or third cycles because of disease progression in 2, grade 3 pneumonitis with pulmonary infiltration in 2, and decreased performance status in 1. Grade 3 toxicities were neutropenia, an increased glutamic pyruvic transaminase level, allergy, pneumonitis, anorexia, and fatigue. Elevation of the serum glutamic oxaloacetic transaminase level after 1 cycle was the only grade 4 toxicity. Seven of 16 patients achieved a partial response and the overall response rate in the prospective study was 43.8%. The median survival time was 18.1 months. The 1- and 2-year survival rates were 56.3% and 43.8%, respectively.

CONCLUSION

Pac and CPT combined with Gef was not effective enough for NSCLC.

RLIP76: a target for kidney cancer therapy

RLIP76 is a multifunctional transporter protein that serves as an energy-dependent efflux mechanism for endogenously generated toxic metabolites as well as exogenous toxins, including chemotherapy drugs. Our recent studies in cultured cells, syngeneic animal tumor model, and in xenograft model have shown that RLIP76 serves a major cancer-specific antiapoptotic role in a wide variety of histologic types of cancer, including leukemia, melanoma, colon, lung, prostate, and ovarian cancer. Results of present studies in cell culture and xenograft model of Caki-2 cells show that RLIP76 is an important anticancer for kidney cancer because inhibition of RLIP76 function by antibody or its depletion by small interfering RNA or antisense DNA caused marked and sustained regression of established human kidney xenografts of Caki-2 cells in nude mouse.

Improving gemcitabine-mediated radiosensitization using molecularly targeted therapy: a review

In the last three decades, gemcitabine has progressed from the status of a laboratory cytotoxic drug to a standard clinical chemotherapeutic agent and a potent radiation sensitizer. In an effort to improve the efficacy of gemcitabine, additional chemotherapeutic agents have been combined with gemcitabine (both with and without radiation) but with toxicity proving to be a major limitation. Therefore, the integration of molecularly targeted agents, which potentially produce less toxicity than standard chemotherapy, with gemcitabine radiation is a promising strategy for improving chemoradiation. Two of the most promising targets, described in this review, for improving the efficacy of gemcitabine radiation are epidermal growth factor receptor and checkpoint kinase 1.

EGFR Inhibition in the Treatment of Non-Small Cell Lung Cancer

Epidermal growth factor receptor (EGFR) inhibitors have introduced the concept of targeted therapy to the treatment of non-small cell lung cancer (NSCLC). These agents appear most effective in patients with tumors that are highly dependent on EGFR signaling pathways, a population that disproportionately includes females, nonsmokers, individuals of East Asian origin, and patients with adenocarcinoma histology. Currently available EGFR-inhibiting drugs include the tyrosine kinase inhibitors (TKIs) erlotinib, gefitinib, and lapatinib, which are administered orally and interfere with the intracellular tyrosine kinase domain, and the monoclonal antibodies (mAbs) cetuximab and panitumumab, which are administered intravenously and interfere with extracellular ligand binding. While the use of EGFR TKIs as monotherapy prolongs survival in metastatic NSCLC, they have demonstrated no benefit when added to conventional, cytotoxic chemotherapy. In contrast, the anti-EGFR mAb cetuximab appears most effective when combined with chemotherapy or radiation. Despite dramatic initial responses to treatment in some cases, NSCLC eventually becomes resistant to EGFR inhibition. Possible mechanisms include secondary mutations that interfere with drug binding, oncogenic pathways driven by other receptor tyrosine kinases, and independent activity of downstream signaling molecules. Efforts to overcome such resistance include irreversibly binding EGFR TKIs, multi-targeted TKIs, and combinations with chemotherapy, radiation, and other targeted therapies.

The combination of epidermal growth factor receptor inhibitors with gemcitabine and radiation in pancreatic cancer

PURPOSE

Gemcitabine-radiotherapy is a standard treatment for locally advanced pancreatic cancer. Clinical data have shown that gemcitabine plus erlotinib is superior to gemcitabine alone for advanced pancreatic cancer. Therefore, we investigated the effects of the combination of epidermal growth factor receptor inhibitors with gemcitabine and radiation on a pancreatic cancer model.

EXPERIMENTAL DESIGN

EGFR signaling was analyzed by measuring phosphorylated EGFR (pEGFR(Y845, (Y1173)) and AKT (pAKT(S473)) protein levels in pancreatic cancer cell lines and tumors. The effects of scheduling on gemcitabine-mediated cytotoxicity and radiosensitization combined with erlotinib were determined by clonogenic survival. In vivo, the effects of cetuximab or erlotinib in combination with gemcitabine-radiation on the growth of BxPC-3 tumor xenografts were measured.

RESULTS

We found in vitro that gemcitabine induced phosphorylation of EGFR at Y845 and Y1173 that was blocked by erlotinib. Treatment of BxPC-3 cells with gemcitabine before erlotinib enhanced gemcitabine-mediated cytotoxicity without abrogating radiosensitization. In vivo, cetuximab or erlotinib in combination with gemcitabine-radiation inhibited growth compared with gemcitabine-radiation (time to tumor doubling: gemcitabine + radiation, 19 +/- 3 days; cetuximab + gemcitabine + radiation, 30 +/- 3 days; P < 0.05, erlotinib + gemcitabine + radiation 28 +/- 3 days; P < 0.1). Cetuximab or erlotinib in combination with gemcitabine-radiation resulted in significant inhibition of pEGFR(Y1173) and pAKT(S473) early in treatment, and pEGFR(Y845), pEGFR(Y1173), and pAKT(S473) by the end of treatment. This study shows a novel difference pEGFR(Y845) and pEGFR(Y1173) in response to EGFR inhibition.

CONCLUSIONS

These results show that the EGFR inhibitors cetuximab and erlotinib increase the efficacy of gemcitabine-radiation. This work supports the integration of EGFR inhibitors with gemcitabine-radiation in clinical trials for pancreatic cancer.

Nab-paclitaxel efficacy in the orthotopic model of human breast cancer is significantly enhanced by concurrent anti-vascular endothelial growth factor A therapy

Nab-paclitaxel is an albumin-bound 130-nm particle form of paclitaxel that has shown an improved efficacy in experimental tumor models and clinical studies compared with solvent-based paclitaxel. Anti-vascular endothelial growth factor A (VEGF-A) antibody bevacizumab is known to enhance antitumor activity of cytotoxic drugs. This study evaluated the effects of combined nab-paclitaxel and bevacizumab therapy on growth and metastatic spread of orthotopic breast tumors. Cytotoxic and clonogenic assays measured VEGF-A-dependent modulation of nabpaclitaxel toxicity on cultured tumor cells. Antitumor effects were assessed in mice with luciferase-tagged, well-established MDA-MB-231 tumors (250-310 mm3) treated with one, two, or three cycles of nab-paclitaxel (10 mg/kg, daily for five consecutive days), bevacizumab (2-8 mg/kg, twice a week), or with combination of both drugs. VEGF-A protected MDA-MB-231 cells against nab-paclitaxel cytotoxicity, whereas bevacizumab sensitized cells to the effect of the drug. Combined bevacizumab and nab-paclitaxel treatment synergistically inhibited tumor growth and metastasis resulting in up to 40% of complete regressions of well-established tumors. This therapy also decreased the incidence of lymphatic and pulmonary metastases by 60% and 100%, respectively. The significant increase in the cure of tumor-bearing mice in the nab-paclitaxel/bevacizumab combined group compared with mice treated with single drugs strongly advocates for implementing such strategy in clinics.

The use of xenograft models for the selection of cancer treatments with the EGFR as an example

Mouse models of cancer have consistently been used to qualify new anti-cancer drugs for development of human clinical trials. The most used models are xenografts of human tumors grown subcutaneously in immunodeficient mice such as athymic (nude) or severe combined immune deficient (SCID) mice. However, the number of anti-cancer agents that fail in the clinic far outweighs those considered effective, suggesting that the selection procedure for progression of molecules into the clinic requires improvement. This has provoked considerable skepticism about the value of using such preclinical models. As a result, a shift has occurred towards developing and using spontaneous mouse tumor arising in transgenic and/or knockout mice engineered to recapitulate various genetic alterations thought to be causative of specific types of human cancers. Alternatively, the option has been to improve human tumor xenograft models by using orthotopic transplantation and, therefore, promotion of metastatic spread of the resultant 'primary' tumors. Here we review the value and the limitations of xenograft models and their role in developing new anti-cancer treatments.

Molecular mechanisms of ZD1839 (Iressa)-induced apoptosis in human leukemic U937 cells

AIM

To investigate the molecular mechanisms of ZD1839-induced apoptosis in human leukemic U937 cells.

METHODS

The inhibition of human leukemic U937 cell growth was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphnyl-2H-tetrazolim bromide (MTT) assays, lactate dehydrogenase (LDH) release, and cell cycle distribution. The expression of anti- and pro-apoptotic proteins was detected by Western blot analysis.

RESULTS

This study demonstrated that ZD1839 induced apoptosis in leukemic U937 cells by the downregulation of Bcl-2, caspase activation and subsequent apoptotic features. Cotreatment with ZD1839 and the caspase-3 inhibitor z-DEVD-fmk blocked apoptosis, indicating that caspase-3 activation is at least partially responsible for ZD1839-induced apoptosis. The ectopic expression of Bcl-2 attenuated caspase-3 activation, PARP cleavage, and subsequent indicators of apoptosis, including sub-G1 DNA content and LDH release. These results indicate that the downregulation of Bcl-2 plays a major role in the initiation of ZD1839-induced apoptosis, and that the activation of a caspase cascade is involved in the execution of apoptosis. Furthermore, ZD1839 treatment triggered the activation of p38 mitogen-activated protein kinase (MAPK) and the down-regulation of c-Jun-N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and phosphatidyl inositol 3-kinase (PI3K)/Akt. The inhibition of the ERK and PI3K/Akt pathways also significantly increased cellular death.

CONCLUSION

ZD1839 activated caspase-3 and the inhibited Bcl-2 in human leukemic U937 cells through the downregulation of the ERK and PI3K/Akt pathways.

Tumor growth inhibition with cetuximab and chemotherapy in non-small cell lung cancer xenografts expressing wild-type and mutated epidermal growth factor receptor

PURPOSE

Targeting the epidermal growth factor receptor (EGFR) is a validated approach to treat cancer. In non-small cell lung cancer (NSCLC), EGFR contains somatic mutations in 10% of patients, which correlates with increased response rates to small molecule inhibitors of EGFR. We analyzed the effects of the monoclonal IgG1 antibody Erbitux (cetuximab) in NSCLC xenografts with wild-type (wt) or mutated EGFR.

EXPERIMENTAL DESIGN

NSCLC cell lines were grown s.c. in nude mice. Dose-dependent efficacy was established for cetuximab. To determine whether combination therapy produces tumor regressions, cetuximab was dosed at half-maximal efficacy with chemotherapy used at maximum tolerated dose.

RESULTS

Cetuximab showed antitumor activity in wt (A549, NCI-H358, NCI-H292) and mutated [HCC-827 (delE746-A750), NCI-H1975 (L858R, T790M)] EGFR-expressing xenografts. In the H292 model, cetuximab and docetaxel combination therapy was more potent to inhibit tumor growth than cetuximab or docetaxel alone. Cisplatin augmented efficacy of cetuximab to produce 6 of 10 regressions, whereas 1 of 10 regressions was found with cetuximab and no regression was found with cisplatin. Using H1975 xenografts, gemcitabine increased efficacy of cetuximab resulting in 12 of 12 regressions. Docetaxel with cetuximab was more efficacious with seven of nine regressions compared with single treatments. Cetuximab inhibited autophosphorylation of EGFR in both H292 and H1975 tumor lysates. Exploring the underlying mechanism for combination effects in the H1975 xenograft model, docetaxel in combination with cetuximab added to the antiproliferative effects of cetuximab but was the main component in this drug combination to induce apoptosis.

CONCLUSIONS

Cetuximab showed antitumor activity in NSCLC models expressing wt and mutated EGFR. Combination treatments increased the efficacy of cetuximab, which may be important for the management of patients with chemorefractory NSCLC.

Cellular responses to EGFR inhibitors and their relevance to cancer therapy

EGFR is a trans-membrane receptor tyrosine kinase that belongs to the HER family of receptors. The EGFR family plays an essential role in normal organ development by mediating morphogenesis and differentiation. Unlike normal cells that have tight regulatory mechanisms controlling EGFR pathways, tumor cells often have dysregulated EGFR signaling through receptor overexpression and/or mutation. This leads to proliferation under adverse conditions, invasion of surrounding tissues, and increased angiogenesis as well as resistance to radiation and chemotherapy. Therefore, EGFR is a legitimate therapeutic target. Numerous EGFR inhibitors are under development, but to date only four of them are FDA-approved, including two that inhibit the receptor's intracellular tyrosine kinase activity (gefitinib and erlotinib) and two that block extracellular ligand binding (cetuximab, and most recently panitumumab). In this review, we focus on how these different inhibitors affect EGFR signaling and the mechanisms by which they potentiate the effects of chemotherapy and radiation therapy. Numerous clinical trials have been conducted with these agents either as monotherapy, in combination with chemotherapy, or concurrently with radiation. Unfortunately, many of the clinical trials reported so far have shown at best limited gains; therefore, understanding the actions of these agents is essential to improving their efficacy in the treatment of cancers.

Concomitant inhibition of epidermal growth factor and vascular endothelial growth factor receptor tyrosine kinases reduces growth and metastasis of human salivary adenoid cystic carcinoma in an orthotopic nude mouse model

We hypothesized that epidermal growth factor (EGF) receptor (EGFR) activation and vascular endothelial growth factor (VEGF)-induced angiogenic signals are important for the progression and metastasis of human salivary adenoid cystic carcinoma (ACC). To test this hypothesis, we evaluated the therapeutic effect of AEE788, a dual inhibitor of EGF and VEGF receptor (VEGFR) tyrosine kinases, on human salivary ACC. In clinical specimens of salivary ACC, EGF and VEGF signaling proteins were expressed at markedly higher levels than in adjacent normal glandular tissues. We examined the effects of AEE788 on salivary ACC cell growth and apoptosis and on the phosphorylation of EGFR and VEGFR-2 in salivary ACC cells. Treatment of salivary ACC cells with AEE788, alone or in combination with chemotherapy, led to growth inhibition, induction of apoptosis, and dose-dependent inhibition of EGFR and VEGFR-2 phosphorylation. To determine the in vivo antitumor effects of AEE788, nude mice with orthotopic parotid tumors were randomized to receive oral AEE788 alone, paclitaxel alone, cisplatin alone, a combination of AEE788 plus paclitaxel, a combination of AEE788 plus cisplatin, or a placebo. AEE788 inhibited tumor growth and prevented lung metastasis in nude mice. To study the mechanism of interaction between AEE788 and chemotherapy, AEE788 was found to potentiate growth inhibition and apoptosis of ACC tumor cells mediated by chemotherapy. Tumors of mice treated with AEE788 and AEE788 plus chemotherapy exhibited down-regulation of activated EGFR and VEGFR-2, increased tumor and endothelial cell apoptosis, and decreased microvessel density, which correlated with a decrease in the level of matrix metalloproteinase-9 and matrix metalloproteinase-2 expression and a decrease in the incidence of vascular metastasis. These data show that EGFR and VEGFR can be molecular targets for therapy of salivary ACC.

Integration of EGFR inhibitors with radiochemotherapy

Laboratory studies that led to the development of epidermal growth factor receptor (EGFR) inhibitors indicated that such inhibitors would be effective when given to patients with tumours that are driven by activated EGFR. However, initial clinical studies have shown modest responses to EGFR inhibitors when used alone, and it has not yet been possible to clearly identify which tumours will respond to this therapy. As a result, EGFR inhibitors are now used in combination with radiation therapy, chemotherapy and, more recently, with concurrent radiochemotherapy. In general, these clinical trials have been designed without much preclinical data. What do we need to know to make these combinations successful in the clinic?

Gefitinib and the modulation of the signaling pathways downstream of epidermal growth factor receptor in human liver cancer cells

BACKGROUND

The transforming growth factor-alpha (TGF-alpha)/epidermal growth factor receptor (EGFR) signaling pathway has been demonstrated to have a pivotal role in hepatocarcinogenesis. We examined whether abrogation of the TGF-alpha/EGFR signaling pathway with a selective EGFR tyrosine kinase inhibitor, gefitinib, could inhibit the proliferation of human hepatocellular carcinoma (HCC) cells.

METHODS

Cellular growth was monitored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Cell-cycle distribution was analyzed by flow cytometric analysis. Activities of signaling molecules were evaluated by Western blot analysis.

RESULTS

HCC cells expressed EGFR at variable levels; however, extracellular signal-regulated kinase (ERK)1/2 and AKT, key signaling molecules downstream of EGFR, were not constitutively active in the cells. When HCC cells were treated with TGF-alpha, cellular growth was accelerated in a manner dependent on activation of ERK1/2 and AKT. When the cells were co-treated with gefitinib and TGF-alpha, enhanced proliferation and activation of ERK1/2 and AKT were canceled, and the cell-cycle promotion by TGF-alpha was inhibited by co-treatment with gefitinib and TGF-alpha, independently of expression levels of EGFR. In contrast, gefitinib did not show an antiproliferative effect on HCC cells cultivated under the 10% serum condition.

CONCLUSIONS

The present data demonstrated that gefitinib exerted an antiproliferative action on HCC cells under a limited condition when signaling pathways downstream of EGFR were activated by TGF-alpha.

Prediction of anticancer drug potency from expression of genes involved in growth factor signaling

PURPOSE

This study develops and evaluates a systematic approach to finding biomarker genes for predicting potency of anticancer drugs against tumor cells, focusing on gene families related to growth factor signaling.

METHODS

Cytotoxic potencies of 119 drugs against 60 neoplastic cell lines (NCI-60) were correlated with expression of 343 genes, including 90 growth factors and receptors, 63 metalloproteinases, and 92 ras-like GTPases as downstream signaling factors. Progressively more stringent criteria and predictive models aim at identifying the smallest subset of genes predictive of cytotoxic potency.

RESULTS

Comparing gene expression with drug potency across the NCI-60 yielded genes with negative and positive correlations (p < 0.001), indicative of a role in chemoresistance and chemosensitivity, respectively. Of 17 genes with multiple negative correlations, 8 are known chemoresistance factors, validating the approach. Negatively correlated genes clustered into two main groups with distinct expression profiles and drug correlations, represented by EGFR and ERBB2 (Her-2/Neu). Accordingly, no synergism was observed between EGFR and ERBB2 inhibitors. However, combinations with classical anticacer drugs were not correlated with EGFR and ERBB2 expression in four cell lines tested, suggesting complex interactions in combination treatments. Finally, a subset of only 13 genes was found to be sufficient for near optimal prediction of drug potency against the NCI-60.

CONCLUSIONS

Our approach using a small subset of genes reveals known and potential biomarkers in cancer chemotherapy, providing a strategy for genome-wide analysis.

EGFR mRNA is Upregulated, but Somatic Mutations of the Gene are Hardly Found in Renal Cell Carcinoma in Japanese Patients

PURPOSE

Heterozygous somatic mutations of epidermal growth factor receptor (EGFR) in exons 18, 19, and 21 were recently reported to be associated with response to gefitinib in patients having nonsmall cell lung cancer. Such mutations are more frequently found among Japanese than Europeans. In this work, the frequency of mutations was investigated in renal cell carcinoma (RCC) samples obtained from Japanese subjects to examine the potential of gefitinib as a therapeutic agent for RCC.

METHODS

Nineteen patients with RCC, who gave written informed consent, were enrolled in this study. mRNA expression levels of EGFR were measured in RCC and its adjacent noncancerous renal tissue via the real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Somatic mutations were determined using genomic DNA extracted from RCC by direct sequencing method.

RESULTS

mRNA expression was confirmed to be about 19 times higher in RCC than in adjacent noncancerous renal tissues, but no such mutations were detected in both.

CONCLUSION

Results from this study do not support the validity of further clinical trials on gefitinib for RCC with genotyping even in Japanese patients, although EGFR plays a key role in tumor progression.

Gene signatures of progression and metastasis in renal cell cancer

PURPOSE

To address the progression, metastasis, and clinical heterogeneity of renal cell cancer (RCC).

EXPERIMENTAL DESIGN

Transcriptional profiling with oligonucleotide microarrays (22,283 genes) was done on 49 RCC tumors, 20 non-RCC renal tumors, and 23 normal kidney samples. Samples were clustered based on gene expression profiles and specific gene sets for each renal tumor type were identified. Gene expression was correlated to disease progression and a metastasis gene signature was derived.

RESULTS

Gene signatures were identified for each tumor type with 100% accuracy. Differentially expressed genes during early tumor formation and tumor progression to metastatic RCC were found. Subsets of these genes code for secreted proteins and membrane receptors and are both potential therapeutic or diagnostic targets. A gene pattern ("metastatic signature") derived from primary tumor was very accurate in classifying tumors with and without metastases at the time of surgery. A previously described "global" metastatic signature derived by another group from various non-RCC tumors was validated in RCC.

CONCLUSION

Unlike previous studies, we describe highly accurate and externally validated gene signatures for RCC subtypes and other renal tumors. Interestingly, the gene expression of primary tumors provides us information about the metastatic status in the respective patients and has the potential, if prospectively validated, to enrich the armamentarium of diagnostic tests in RCC. We validated in RCC, for the first time, a previously described metastatic signature and further showed the feasibility of applying a gene signature across different microarray platforms. Transcriptional profiling allows a better appreciation of the molecular and clinical heterogeneity in RCC.

A phase II, open-label study of gefitinib (IRESSA) in patients with locally advanced, metastatic, or relapsed renal-cell carcinoma

Epidermal growth factor receptor (EGFR) expression has been associated with clinical outcome in some studies of renal-cell carcinoma (RCC). We investigated the efficacy and safety of gefitinib (IRESSA), an EGFR tyrosine kinase inhibitor, in RCC patients. This phase II trial recruited 28 patients with advanced, metastatic, or relapsed RCC. Patients received oral gefitinib 500 mg/day. Objective responses (ORs) were assessed every 2 months according to RECIST. Baseline tumor biopsies were analyzed immunohistochemically for EGFR expression. At trial closure (March 2003), no ORs were seen but 14 patients (53.8%) had stable disease. At extended analysis (August 2004), median time to progression was 110 days (95% confidence interval [CI]: 55, 117); median overall survival was 303 days (95% CI 180, 444). Gefitinib was generally well tolerated. Skin rash and diarrhea were the most common drug-related adverse events (AEs) [54 and 39% of patients, respectively] and the most common drug-related grade 3/4 AEs (both 11%). The majority of tumor biopsies (91%) had > or =70% of tumor cells expressing membrane EGFR. Despite the lack of ORs in this study, disease control was observed in 53.8% of patients. Gefitinib was generally well tolerated and no unexpected drug-related AEs were observed.

The effect of ZD1839 (Iressa), an epidermal growth factor receptor tyrosine kinase inhibitor, in combination with cisplatin, on apoptosis in SCC-15 cells

The aim of this study was to determine the effect of ZD1839 on growth and apoptosis in SCC-15 (a human head and neck cancer cell line) lone, or in combination with cisplatin. High expression of the epidermal growth factor receptor has been implicated in the development of squamous cell carcinomas of head and neck. ZD1839 ('Iressa') is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor that blocks signal transduction pathways implicated in proliferation and survival of cancer cells, and other host-dependent processes promoting cancer growth. Here, growth arrest was observed with 3.64 microm ZD1839. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (sMTT) viability assay revealed a significant decrease (P < 0.001) in the percentage of surviving cells upon treatment with ZD1839 and cisplatin compared with cisplatin or ZD1839 on their own. Combined therapy of 3.64 microm ZD1839 for 24 h, prior to administration of 100 microm cisplatin, significantly (P < 0.001) and additively increased the cytotoxicity effect of cisplatin. p53-independent apoptosis was seen with cisplatin treatment, a novel finding. These data support the use of ZD1839 in anti-cancer therapy, and particularly in combination therapy. Cisplatin may induce p53-independent apoptosis. Over-expression of Bcl-2 in head and neck squamous cell carcinoma tumour cell lines is unlikely to be a general mechanism to protect these cells from apoptosis.

Protein-interaction mapping in search of effective drug targets

Signaling complexes and networks are being intensely studied in an attempt to discover pathways that are amenable to therapeutic intervention. A challenge in this search is to understand the effect that the modulation of a target will have on the overall function of a cell and its surrounding neighbors. Protein-interaction mapping reveals relationships between proteins and their impact on cellular processes and is being used more widely in our understanding of disease mechanisms and their treatment. The review discusses challenges and breakthroughs in this new and evolving area and its impact on medicine.