Integration of Epidermal Growth Factor Receptor Inhibitors with Preoperative Chemoradiation: Fig. 1

The therapeutic targets of N6-methyladenosine (m6A) modifications on tumor radioresistance

Radiation therapy is an important tool for malignant tumors, and its tolerance needs to be addressed. In recent years, several studies have shown that regulators of aberrant m6A methylation play an important role in the formation, development and invasion and metastasis of tumors. A large number of studies have confirmed aberrant m6A methylation as a new target for tumour therapy, but research on whether it can play a role in tumor sensitivity to radiotherapy has not been extensive and thorough enough. Recent studies have shown that all three major enzymes of m6A methylation have significant roles in radioresistance, and that the enzymes that play a role differ in different tumor types and by different mechanisms, including regulating tumor cell stemness, affecting DNA damage and repair, and controlling the cell cycle. Therefore, elucidating the mechanisms of m6A methylation in the radiotherapy of malignant tumors is essential to counteract radioresistance, improve the efficacy of radiotherapy, and even propose targeted treatment plans for specific tumors. The latest research progress on m6A methylation and radioresistance is reviewed in this article.

Simultaneous inhibition of IGF1R and EGFR enhances the efficacy of standard treatment for colorectal cancer by the impairment of DNA repair and the induction of cell death

Overexpression and activation of receptor tyrosine kinases (RTKs), such as the insulin-like growth factor 1 receptor (IGF1R) and the epidermal growth factor receptor (EGFR), are frequent phenomena in colorectal cancer (CRC). Here, we evaluated the effect and the cellular mechanisms of the simultaneous inhibition of these two RTKs both in vitro and in vivo in addition to a 5-fluoruracil (5-FU)-based radiochemotherapy (RCT), which is a standard treatment scheme for CRC. Using the small molecule inhibitors AEW541 and erlotinib, specific against IGF1R and EGFR, respectively, different CRC cell lines exhibited a reduced survival fraction after RCT, with the highest effect after the simultaneous inhibition of IGF1R/EGFR. In vivo, xenograft mice simultaneously treated with low dose AEW541/erlotinib plus RCT revealed a significant reduction in tumour volume and weight compared with the tumours of mice treated with either AEW541 or erlotinib alone. In vitro, the combined inhibition of IGF1R/EGFR resulted in a stronger reduction of downstream signalling, an increase in DNA double strand breaks (DSBs), apoptosis and mitotic catastrophe after RCT depending on the cell line. Moreover, the existence of IGF1R/EGFR heterodimers in CRC cells and human rectal cancer samples was proven. The heterodimerisation of these RTKs was dependent on the presence of both ligands, IGF-1 and EGF, and functional receptors. In conclusion, these results demonstrate that the strategy of targeting both IGF1R and EGFR, in addition to basic RCT, could be of intriguing importance in CRC therapy.

In vitro and in vivo evaluation of the radiosensitizing effect of a selective FGFR inhibitor (JNJ-42756493) for rectal cancer

Background

We examined the anti-tumor effect and radiosensitizing potential of a small molecule inhibitor of fibroblast growth factor receptor (FGFR) in colorectal cancer (CRC) in vitro and in vivo.

Methods

Effects of in vitro drug treatment on cell survival, proliferation, FGFR signaling, cell cycle distribution, apoptosis and radiosensitivity were assessed using various CRC cell lines with FGFR wild type (Caco2 and HCA7) and FGFR2 amplification (HCT116, NCI-H716). In vivo tumor responses to FGFR inhibition with and without radiation therapy were evaluated by growth delay assays in two colorectal xenograft mouse models (NMRI nu/nu mice injected with NCI-H716 or CaCo2 cells). Mechanistic studies were conducted using Western blot analysis, immunohistochemistry and qPCR.

Results

In the tested cell lines, the FGFR inhibitor (JNJ-42756493) was effective in vitro and in vivo in CRC tumors with highest expression of FGFR2 (NCI-H716). In vitro, cell proliferation in this line was decreased, associated with increased apoptotic death and decreased cell survival. In vivo, growth of NCI-H716 tumors was delayed by 5 days by drug treatment alone, although when drug delivery was stopped the relative tumor volume increased compared to control. The FGFR inhibitor did not radiosensitize NCI-H716 tumors either in vitro or in vivo.

Conclusions

Among tested CRC cell lines, the growth inhibitory activity of this FGFR inhibitor was evident in cell lines with high constitutive FGFR2 expression, suggesting that FGFR addiction may provide a window for therapeutic intervention, though caution is advised. Preclinical study with NCI-H716 and Caco2 tumor demonstrated that continued presence of drug could be essential for tumor growth control, especially in cells with aberrant FGFR expression. In the tested set-up, the inhibitor showed no radiosensitizing effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-2000-8) contains supplementary material, which is available to authorized users.

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.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

Concomitant EGFR inhibitors combined with radiation for treatment of non-small cell lung carcinoma

Epidermal growth factor receptor (EGFR) is considered to be one of the key driver genes in non-small cell lung cancer (NSCLC). Several clinical trials have shown great promise of EGFR tyrosine kinase inhibitors (TKIs) in the first-line treatment of NSCLC. Many advances have been made in the understanding of EGFR signal transduction network and the interaction between EGFR and tumor microenvironment in mediating cancer survival and development. The concomitant targeted therapy and radiation is a new strategy in the treatment of NSCLC. A number of preclinical studies have demonstrated synergistic anti-tumor activity in the combination of EGFR inhibitors and radiotherapy in vitro and in vivo. In the present review, we discuss the rationale of the combination of EGFR inhibitors and radiotherapy in the treatment of NSCLC.

Comparative analysis of radiosensitizers for K-RAS mutant rectal cancers

Approximately 40% of rectal cancers harbor activating K-RAS mutations, and these mutations are associated with poor clinical response to chemoradiotherapy. We aimed to identify small molecule inhibitors (SMIs) that synergize with ionizing radiation (IR) ("radiosensitizers") that could be incorporated into current treatment strategies for locally advanced rectal cancers (LARCs) expressing mutant K-RAS. We first optimized a high-throughput assay for measuring individual and combined effects of SMIs and IR that produces similar results to the gold standard colony formation assay. Using this screening platform and K-RAS mutant rectal cancer cell lines, we tested SMIs targeting diverse signaling pathways for radiosensitizing activity and then evaluated our top hits in follow-up experiments. The two most potent radiosensitizers were the Chk1/2 inhibitor AZD7762 and the PI3K/mTOR inhibitor BEZ235. The chemotherapeutic agent 5-fluorouracil (5-FU), which is used to treat LARC, synergized with AZD7762 and enhanced radiosensitization by AZD7762. This study is the first to compare different SMIs in combination with IR for the treatment of K-RAS mutant rectal cancer, and our findings suggest that Chk1/2 inhibitors should be evaluated in new clinical trials for LARC.

Radiation-induced Notch signaling in breast cancer stem cells

PURPOSE

To explore patterns of Notch receptor and ligand expression in response to radiation that could be crucial in defining optimal dosing schemes for γ-secretase inhibitors if combined with radiation.

METHODS AND MATERIALS

Using MCF-7 and T47D breast cancer cell lines, we used real-time reverse transcription-polymerase chain reaction to study the Notch pathway in response to radiation.

RESULTS

We show that Notch receptor and ligand expression during the first 48 hours after irradiation followed a complex radiation dose-dependent pattern and was most pronounced in mammospheres, enriched for breast cancer stem cells. Additionally, radiation activated the Notch pathway. Treatment with a γ-secretase inhibitor prevented radiation-induced Notch family gene expression and led to a significant reduction in the size of the breast cancer stem cell pool.

CONCLUSIONS

Our results indicate that, if combined with radiation, γ-secretase inhibitors may prevent up-regulation of Notch receptor and ligand family members and thus reduce the number of surviving breast cancer stem cells.

Hedgehog signaling in prostate cancer and its therapeutic implication

Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition.

Recurrent oral cancer: current and emerging therapeutic approaches

Oral cavity cancer (OCC) is associated with high incidence of loco-regional recurrences, which account for the majority of treatment failures post-surgery and radiotherapy. The time-course of relapse manifestation and metastasis are unpredictable. Relapsed OCC represents a major clinical challenge in part due to their aggressive and invasive behaviors. Chemotherapy remains the only option for advanced OCC whenever salvage surgery or re-irradiation is not feasible, but its efficacy is limited as a result of the drug resistance development. Alternatives to use of different permutations of standard cytotoxic drugs or combinations with modulators of drug resistance have led to incremental therapeutic benefits. The introduction of targeted agents and biologics against selective targets that drive cancer progression has opened-up optimism to achieve superior therapeutic activity and overcome drug resistance because, unlike the non-selective cytotoxic, the target can be monitored at molecular levels to identify patients who can benefit from the drug. This review discusses the multifactorial aspects of clinical drug resistance and emerging therapeutic approaches in recurrent OCC, emphasizing recent advances in targeted therapies, immunotherapy, and potential relevance of new concepts such as epithelial-mesenchymal transition and cancer stem cell hypothesis to drug resistance.

KRAS mutation status and clinical outcome of preoperative chemoradiation with cetuximab in locally advanced rectal cancer: a pooled analysis of 2 phase II trials

PURPOSE

Cetuximab-containing chemotherapy is known to be effective for KRAS wild-type metastatic colorectal cancer; however, it is not clear whether cetuximab-based preoperative chemoradiation confers an additional benefit compared with chemoradiation without cetuximab in patients with locally advanced rectal cancer.

METHODS AND MATERIALS

We analyzed EGFR, KRAS, BRAF, and PIK3CA mutation status with direct sequencing and epidermal growth factor receptor (EGFR) and Phosphatase and tensin homolog (PTEN) expression status with immunohistochemistry in tumor samples of 82 patients with locally advanced rectal cancer who were enrolled in the IRIX trial (preoperative chemoradiation with irinotecan and capecitabine; n=44) or the ERBIRIX trial (preoperative chemoradiation with irinotecan and capecitabine plus cetuximab; n=38). Both trials were similarly designed except for the administration of cetuximab; radiation therapy was administered at a dose of 50.4 Gy/28 fractions and irinotecan and capecitabine were given at doses of 40 mg/m2 weekly and 1650 mg/m2/day, respectively, for 5 days per week. In the ERBIRIX trial, cetuximab was additionally given with a loading dose of 400 mg/m2 on 1 week before radiation, and 250 mg/m2 weekly thereafter.

RESULTS

Baseline characteristics before chemoradiation were similar between the 2 trial cohorts. A KRAS mutation in codon 12, 13, and 61 was noted in 15 (34%) patients in the IRIX cohort and 5 (13%) in the ERBIRIX cohort (P=.028). Among 62 KRAS wild-type cancer patients, major pathologic response rate, disease-free survival and pathologic stage did not differ significantly between the 2 cohorts. No mutations were detected in BRAF exon 11 and 15, PIK3CA exon 9 and 20, or EGFR exon 18-24 in any of the 82 patients, and PTEN and EGFR expression were not predictive of clinical outcome.

CONCLUSIONS

In patients with KRAS wild-type locally advanced rectal cancer, the addition of cetuximab to the chemoradiation with irinotecan plus capecitabine regimen was not associated with improved clinical outcome compared with chemoradiation without cetuximab.

The molecular basis of chemoradiosensitivity in rectal cancer: implications for personalized therapies

Introduction

Preoperative chemoradiotherapy represents the standard treatment for patients with locally advanced rectal cancer. Unfortunately, the response of individual tumors to multimodal treatment is not uniform and ranges from complete response to complete resistance. This poses a particular problem for patients with a priori resistant tumors because they may be exposed to irradiation and chemotherapy, treatment regimens that are both expensive and at times toxic, without benefit. Accordingly, there is a strong need to establish molecular biomarkers that predict the response of an individual patient’s tumor to multimodal treatment and that indicate treatment-associated toxicities prior to therapy. Such biomarkers may guide clinicians in choosing the best possible treatment for each individual patient. In addition, these biomarkers could be used to identify novel molecular targets and thereby assist in implementing novel strategies to sensitize a priori resistant tumors to multimodal treatment regimens.

Objective

The aim of this review is to summarize recent findings about the molecular basis of treatment resistance and treatment toxicity in patients with rectal cancer. Whole-genome, as well as single-biomarker or multibiomarker, analyses and their potential implications will be highlighted. At the end, we will outline a future vision of rectal cancer treatment in the era of personalized medicine.

A phase II study of neoadjuvant bevacizumab plus capecitabine and concomitant radiotherapy in patients with locally advanced rectal cancer

PURPOSE

To assess safety and activity of neoadjuvant bevacizumab, capecitabine and standard radiotherapy in locally advanced rectal cancer as well as potential predictive biomarkers.

PATIENTS AND METHODS

The multicentric phase II study enrolled 43 patients who received bevacizumab infusion (5 mg/kg) every 2 weeks for 4 cycles; oral capecitabine at 825 mg/m(2) twice a day for 5.5 weeks with external-beam irradiation (50.4 Gy in 28 fractions over 5.5 weeks). We determined certain biomarkers before and after therapy for correlation with response.

RESULTS

Post-operative histologic examination revealed no residual cancer cells in 6 of the 43 patients (14%; 95% confidence limits 3.60-24.31%). In another 22 patients (51.2%) a varying percentage of cancer cells in residual areas of fibrosis/ necrosis was found, corresponding to Mandard TRG 2 or 3 classification. Tumor resection with negative circumferential margin was achieved in 38/40 (95%) operated patients. Sphincter-sparing surgery was obtained in 31 (72.1%) patients. Primary tumor and lymph nodes downstaging was observed in 15 (34.9%) and 16 (37.2%) cases, respectively. Neoadjuvant therapy was safe and well tolerated. The most frequent side effects were G1-2 diarrhea, proctitis, rectal bleeding and hypertension. No biomarker tested was significantly predictive of both pathological complete response and disease-free survival. Pre-treatment CD-34 vessel density, post-treatment Ki-67 labeling index and VEGFR-2 cancer cells expression significantly correlated with residual tumor area.

CONCLUSIONS

The schedule of neoadjuvant therapy tested was safe and active. Pre-treatment vessel density by the panendothelial marker anti CD-34 antibody, post-treatment Ki-67 labeling index and VEGFR-2 expression were significantly associated to residual tumor area. The biomarkers correlations warrant further evaluation in prospective clinical trials.

Molecular mechanisms of cigarette smoke-induced proliferation of lung cells and prevention by vitamin C

Lung cancer is the leading cause of cancer dearth. Cigarette smoking is the strongest risk factor for developing lung cancer, which is conceivably initiated by proliferation. Here, we show that low concentration of aqueous extract of cigarette smoke (AECS) causes excessive proliferation of human lung epithelial cells (A549) without any apoptotic cell death. The causative factor responsible for AECS-induced proliferation has been identified as p-benzoquinone (p-BQ). Coimmunoprecipitation and immunoblot experiments indicate that p-BQ binds with epidermal growth factor receptor (EGFR). However, in contrast to EGF, it causes aberrant phosphorylation of EGFR that lacks c-Cbl-mediated ubiquitination and degradation resulting in persistent activation of EGFR. This is followed by activation of Hras + Kras and the downstream survival and proliferative signaling molecules Akt and ERK1/2, as well as the nuclear transcription factors c-Myc and c-Fos. Vitamin C and/or antibody to p-BQ prevents AECS/p-BQ-induced proliferation of lung cells apparently by inactivating p-BQ and thereby preventing activation of EGFR and the downstream signaling molecules. The results suggest that vitamin C and/or antibody to p-BQ may provide a novel intervention for preventing initiation of lung cancer in smokers.

Predictive factors of the response of rectal cancer to neoadjuvant radiochemotherapy

Locally advanced rectal cancer is currently treated with pre-operative radiochemotherapy (pRCT), but the response is not uniform. Identification of patients with higher likelihood of responding to pRCT is clinically relevant, as patients with resistant tumors could be spared exposure to radiation or DNA-damaging drugs that are associated with adverse side effects. To highlight predictive biomarkers of response to pRCT, a systematic search of PubMed was conducted with a combination of the following terms: "rectal", "predictive", "radiochemotherapy", "neoadjuvant", "response" and "biomarkers". Genetic polymorphisms in epithelial growth factor receptor (EGFR) and thymidylate synthase (TS) genes, the expression of several markers, such as EGFR, bcl-2/bax and cyclooxygenase (COX)-2, and circulating biomarkers, such as serum carcinoembryonic antigen (CEA) level, are promising as predictor markers, but need to be further evaluated. The majority of the studies did not support the predictive value of p53, while the values of Ki-67, TS and p21 is still controversial. Gene expression profiles of thousands of genes using microarrays, microRNA studies and the search for new circulating molecules, such as human telomerase reverse transcriptase mRNA and cell-free DNA, are providing interesting results that might lead to the identification of new useful biomarkers. Evaluation of biomarkers in larger, prospective trials are required to guide therapeutic strategies.