Epidermal growth factor and ionizing radiation up-regulate the DNA repair genes XRCC1 and ERCC1 in DU145 and LNCaP prostate carcinoma through MAPK signaling

Reactivation of nucleases with peroxidation damages induced by a menadione: ascorbate combination devastates human prostate carcinomas: ultrastructural aspects

INTRODUCTION

Xenografts of androgen-independent human DU145 prostate metastatic carcinomas implanted in nu/nu male mice have revealed a significant survival after a prooxidant anticancer treatment consisting of a combination of menadione bisulfite and sodium ascorbate (VK3:VC).

METHODS

Implanted samples of diaphragm carcinomas from longest survived mice from either oral, intraperitoneal (IP), or both oral and IP treatment groups were assessed with light, scanning, and transmission electron microscopy to analyze morphologic damages.

RESULTS

Compared with previous fine structure data of in vitro untreated carcinomas, the changes induced by oral, IP, and oral with IP VK3:VC treatment dismantled those xenografts with autoschizis, and necrotic atrophy was accomplished by cell's oxidative stress whose injuries were consequent to reactivated deoxyribonucleases and ribonucleases. Tumor destructions resulted from irreversible damages of nucleus components, endoplasmic reticulum, and mitochondria there. Other alterations included those of the cytoskeleton that resulted in characteristic self-excisions named " autoschizis." All these injuries lead resilient cancer cells to necrotic cell death.

CONCLUSION

The fine structure damages caused by VK3:VC prooxidant combination in the human DU145 prostate xenografts confirmed those shown in vitro and of other cell lines with histochemistry and biomolecular investigations. These devastations incurred without damage to normal tissues; thus, our data brought support for the above combination to assist in the treatment of prostate cancers and other cancers.

Epidermal growth factor receptor dual-target inhibitors as a novel therapy for cancer: A review

Overexpression of the epidermal growth factor receptor (EGFR) has been linked to several human cancers, including esophageal cancer, pancreatic cancer, anal cancer, breast cancer, and lung cancer, particularly non-small cell lung cancer (NSCLC). Therefore, EGFR has emerged as a critical target for treating solid tumors. Many 1st-, 2nd-, 3rd-, and 4th-generation EGFR single-target inhibitors with clinical efficacy have been designed and synthesized in recent years. Drug resistance caused by EGFR mutations has posed a significant challenge to the large-scale clinical application of EGFR single-target inhibitors and the discovery of novel EGFR inhibitors. Therapeutic methods for overcoming multipoint EGFR mutations are still needed in medicine. EGFR dual-target inhibitors are more promising than single-target inhibitors as they have a lower risk of drug resistance, higher efficacy, lower dosage, and fewer adverse events. EGFR dual-target inhibitors have been developed sequentially to date, providing new options for remission in patients with previously untreatable malignancies and laying the groundwork for a future generation of compounds. This paper introduces the EGFR family proteins and their synergistic effects with other anticancer targets, and provides a comprehensive review of the development of EGFR dual-target inhibitors in cancer, as well as the opportunities and challenges associated with those fields.

KZ02 enhances the radiosensitivity of BRAF-mutated CRC in vitro and in vivo

Colorectal cancer (CRC) is a common malignant tumor with a high incidence and mortality worldwide. Preoperative chemoradiotherapy is a common treatment for patients with metastatic colorectal cancer (mCRC) as it reduces colostomy and local recurrence. The RAS (rat sarcoma)-RAF (extracellular signal-regulated kinase)-MEK (mitogen-activated protein kinase)-ERK (extracellular signal-regulated kinase) pathway regulates important cellular processes in the CRC. Abnormal ERK activation stimulates cell growth and provides a survival advantage. Our group has previously reported that the compound KZ02 has a stronger ability to inhibit tumor growth than AZD6244 (a MEK inhibitor). In this study, we evaluated the antitumor activity of KZ02 in combination with ionizing radiation (IR) and investigated its mechanism of action in BRAF-mutated colorectal cancer. Our results showed that this combination kills tumor cells better than either radiation or drugs alone, both in vivo and in vitro. Furthermore, studies have shown that KZ02 inhibits ERK overactivation. The combination resulted in a G1 phase arrest, a reduction in the radioresistant S phase, and aggravating DNA damage. It can also inhibit Pim-1 (Moloney murine leukemia virus-1), p-BAD (Bcl-2 associated agonist of cell death), Bcl-2 (B-cell lymphoma 2) and Bcl-XL (B-cell lymphoma-extra large) levels and promote apoptosis when combined with radiation. Our results suggest that KZ02 significantly increases the radiosensitivity of BRAF-mutated CRC cells by perturbing the cell cycle, increasing DNA damage, and promoting tumor apoptosis.

METTL3 promotes homologous recombination repair and modulates chemotherapeutic response in breast cancer by regulating the EGF/Rad51 axis

METTL3 and N6-methyladenosine (m6A) are involved in many types of biological and pathological processes, including DNA repair. However, the function and mechanism of METTL3 in DNA repair and chemotherapeutic response remain largely unknown. In present study, we identified that METTL3 participates in the regulation of homologous recombination repair (HR), which further influences chemotherapeutic response in both MCF-7 and MDA-MB-231 breast cancer (BC) cells. Knockdown of METTL3 sensitized these BC cells to Adriamycin (ADR; also named as doxorubicin) treatment and increased accumulation of DNA damage. Mechanically, we demonstrated that inhibition of METTL3 impaired HR efficiency and increased ADR-induced DNA damage by regulating m6A modification of EGF/RAD51 axis. METTL3 promoted EGF expression through m6A modification, which further upregulated RAD51 expression, resulting in enhanced HR activity. We further demonstrated that the m6A 'reader', YTHDC1, bound to the m6A modified EGF transcript and promoted EGF synthesis, which enhanced HR and cell survival during ADR treatment in breast cancer cells. Our findings reveal a pivotal mechanism of METTL3-mediated HR and chemotherapeutic drug response, which may contribute to cancer therapy.

Development of Dual Inhibitors Targeting Epidermal Growth Factor Receptor in Cancer Therapy

Epidermal growth factor receptor (EGFR) is of great significance in mediating cell signaling transduction and tumor behaviors. Currently, third-generation inhibitors of EGFR, especially osimertinib, are at the clinical frontier for the treatment of EGFR-mutant non-small-cell lung cancer (NSCLC). Regrettably, the rapidly developing drug resistance caused by EGFR mutations and the compensatory mechanism have largely limited their clinical efficacy. Given the synergistic effect between EGFR and other compensatory targets during tumorigenesis and tumor development, EGFR dual-target inhibitors are promising for their reduced risk of drug resistance, higher efficacy, lower dosage, and fewer adverse events than those of single-target inhibitors. Hence, we present the synergistic mechanism underlying the role of EGFR dual-target inhibitors against drug resistance, their structure-activity relationships, and their therapeutic potential. Most importantly, we emphasize the optimal target combinations and design strategies for EGFR dual-target inhibitors and provide some perspectives on new challenges and future directions in this field.

Cell Signaling Pathways That Promote Radioresistance of Cancer Cells

Radiation therapy (RT) is a standard treatment for solid tumors and about 50% of patients with cancer, including pediatric cancer, receive RT. While RT has significantly improved the overall survival and quality of life of cancer patients, its efficacy has still been markedly limited by radioresistance in a significant number of cancer patients (intrinsic or acquired), resulting in failure of the RT control of the disease. Radiation eradicates cancer cells mainly by causing DNA damage. However, radiation also concomitantly activates multiple prosurvival signaling pathways, which include those mediated by ATM, ATR, AKT, ERK, and NF-κB that promote DNA damage checkpoint activation/DNA repair, autophagy induction, and/or inhibition of apoptosis. Furthermore, emerging data support the role of YAP signaling in promoting the intrinsic radioresistance of cancer cells, which occurs through its activation of the transcription of many essential genes that support cell survival, DNA repair, proliferation, and the stemness of cancer stem cells. Together, these signaling pathways protect cancer cells by reducing the magnitude of radiation-induced cytotoxicity and promoting radioresistance. Thus, targeting these prosurvival signaling pathways could potentially improve the radiosensitivity of cancer cells. In this review, we summarize the contribution of these pathways to the radioresistance of cancer cells.

Rational Design and Synthesis of Novel Dual PROTACs for Simultaneous Degradation of EGFR and PARP

Inspired by the success of dual-targeting drugs, especially bispecific antibodies, we propose to combine the concept of proteolysis targeting chimera (PROTAC) and dual targeting to design and synthesize dual PROTAC molecules with the function of degrading two completely different types of targets simultaneously. A library of novel dual-targeting PROTAC molecules has been rationally designed and prepared. A convergent synthetic strategy has been utilized to achieve high synthetic efficiency. These dual PROTAC structures are characterized using trifunctional natural amino acids as star-type core linkers to connect two independent inhibitors and E3 ligands together. In this study, gefitinib, olaparib, and CRBN or VHL E3 ligands were used as substrates to synthesize novel dual PROTACs. They successfully degraded both the epidermal growth factor receptor (EGFR) and poly(ADP-ribose) polymerase (PARP) simultaneously in cancer cells. Being the first successful example of dual PROTACs, this technique will greatly widen the range of application of the PROTAC method and open up a new field for drug discovery.

Design and Mechanism of Action of a New Prototype of Combi-Molecule "Programed" to Release Bioactive Species at a pH Range Akin to That of the Tumor Microenvironment

The clinical use of cytotoxic agents is plagued by systemic toxicity. We report a novel approach that seeks to design a “combi-molecule” to behave as an alkylating agent on its own and to undergo acid-catalyzed conversion to two bioactive species at a pH range akin to that of a tumor microenvironment: an AL530 prototype was synthesized and we studied its ability to release a chlorambucil analogue (CBL-A) plus a potent mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059) at different pHs in buffered solutions, plasma and tumors. Its potency was compared in vitro with CBL+PD98059 (SRB assay) and in vivo in a xenograft model. Its target modulation was studied by western blotting and immunohistochemistry. AL530 released PD98059+CBL-A at mild acidic pH and in vitro was fivefold more potent than CBL and three-to-fivefold more potent than CBL+PD98059. In vivo it released high levels of PD98059 in tumors with a tumor/plasma ratio of five. It induced γ-H2AX phosphorylation and blocked pErk1,2, indirectly indicating its ability to damage DNA and modulate MEK. It induced significant tumor delay and less toxicity at unachievable doses for CBL and CBL+PD98059. We demonstrated the feasibility of a pH-labile combi-molecule capable of delivering high MEK inhibitor concentration in tumors, damaging DNA therein, and inducing tumor growth delay.

Design and Synthesis of a Trifunctional Molecular System "Programmed" to Block Epidermal Growth Factor Receptor Tyrosine Kinase, Induce High Levels of DNA Damage, and Inhibit the DNA Repair Enzyme (Poly(ADP-ribose) Polymerase) in Prostate Cancer Cells

Resistance to chemotherapy in advanced cancers can be mediated by different factors such as epidermal growth factor receptor (EGFR) overexpression and DNA repair enzymes. Therefore, current standards of care usually involve combinations of multiple treatments. Here, to reduce the adverse effects of multiple drug combinations and improve outcome, we proposed a single drug approach to block multiple overlapping effects that characterize chemoresistance. Thus, we designed a new linker that allows assembly of multiple functions (e.g., inhibition of EGFR phosphorylation, induction of DNA lesions, and blockade of their repair) into a single molecule. This led to the successful synthesis of a novel and potent combi-molecule JS230. Here, we demonstrated that in resistant prostate cancer cells overexpressing EGFR, it was capable of (a) inhibiting EGFR in a dose-dependent manner, (b) damaging DNA, and (c) sustaining the damage by inhibiting the DNA repair protein poly(ADP-ribose) polymerase (PARP). The triple mechanism of action of JS230 cumulated into growth inhibitory potency superior to that of classical two- or three-drug combinations.

Dual effects of active ERK in cancer: A potential target for enhancing radiosensitivity

Ionizing radiation (IR) is an important cancer treatment approach. However, radioresistance eventually occurs, resulting in poor outcomes in patients with cancer. Radioresistance is associated with multiple signaling pathways, particularly pro-survival signaling pathways. The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade is an important signaling pathway that initiates several cellular processes and is regulated by various stimuli, including IR. Although numerous studies have demonstrated the pro-survival effects of active ERK, activation of ERK has also been associated with cell death, indicating that radiosensitization may occur by ERK stimulation. In this context, the present review describes the associations between ERK signaling, cancer and IR, and discusses the association between ERK and its pro-survival function in cancer cells, including stimuli, molecular mechanisms, clinical use of inhibitors and underlying limitations. Additionally, the present review introduces the view that active ERK may induce cell death, and describes the potential factors associated with this process. This review describes the various outcomes induced by active ERK to prompt future studies to aim to enhance radiosensitivity in the treatment of cancer.

Role of Cervical Cancer Radiotherapy in the Expression of EGFR and p53 Gene

Background:

Cervical cancer arises from the cervix and it is the 3rd most diagnosed malignancy and a foremost cause of cancer-related death in females. On the other hand, the expressions of EGFR and p53 are two important proteins observed in various studies on cervical cancer.

Objective:

The study aims to evaluate the beneficial effect of radiotherapy based on the regulation of p53 and EGFR gene in patients with cervical cancer.

Methods:

In this investigation, the regulation of important molecules responsible for cancer cell proliferation and DNA repair in the cervical cancer cell line was evaluated. The study comprises of an evaluation based on clinical study design from the malignant biopsies of 15 cervical cancer patients. The patterns of expression for the p53 gene and Epidermal Growth Factor Receptor (EGFR) were evaluated in DoTc2 and SiHa cervical cancer cell lines using clonogenic assay, western blotting and immunohistochemistry techniques from the malignant biopsies of the 15 patients.

Results:

The study observed that the regulation of p53 and EGFR was very weak after the exposure of the radiation. In addition, the expression of p53 and EGFR was observed in malevolent biopsy samples after radiation with a dosage of 1.8 Gy radiations. Additionally, the expression of p53 and EGFR was able to induce by a single dose of radiotherapy in the malignant biopsies whereas it was unable to induce in DoTc2 and SiHa cervical cancer cells.

Conclusion:

The study observed that radiation exposed cancer cell lines modulates the expression of p53 and EGFR gene. The study also highlights the gap between in vitro experimental models and clinical study design.

Mechanisms and Antitumor Activity of a Binary EGFR/DNA-Targeting Strategy Overcomes Resistance of Glioblastoma Stem Cells to Temozolomide

PURPOSE

Glioblastoma (GBM) is a fatal primary malignant brain tumor. GBM stem cells (GSC) contribute to resistance to the DNA-damaging chemotherapy, temozolomide. The epidermal growth factor receptor (EGFR) displays genomic alterations enabling DNA repair mechanisms in half of GBMs. We aimed to investigate EGFR/DNA combi-targeting in GBM.

EXPERIMENTAL DESIGN

ZR2002 is a "combi-molecule" designed to inflict DNA damage through its chlorethyl moiety and induce irreversible EGFR tyrosine kinase inhibition. We assessed its in vitro efficacy in temozolomide-resistant patient-derived GSCs, mesenchymal temozolomide-sensitive and resistant in vivo-derived GSC sublines, and U87/EGFR isogenic cell lines stably expressing EGFR/wild-type or variant III (EGFRvIII). We evaluated its antitumor activity in mice harboring orthotopic EGFRvIII or mesenchymal TMZ-resistant GSC tumors.

RESULTS

ZR2002 induced submicromolar antiproliferative effects and inhibited neurosphere formation of all GSCs with marginal effects on normal human astrocytes. ZR2002 inhibited EGF-induced autophosphorylation of EGFR, downstream Erk1/2 phosphorylation, increased DNA strand breaks, and induced activation of wild-type p53; the latter was required for its cytotoxicity through p53-dependent mechanism. ZR2002 induced similar effects on U87/EGFR cell lines and its oral administration significantly increased survival in an orthotopic EGFRvIII mouse model. ZR2002 improved survival of mice harboring intracranial mesenchymal temozolomide-resistant GSC line, decreased EGFR, Erk1/2, and AKT phosphorylation and was detected in tumor brain tissue by MALDI imaging mass spectrometry.

CONCLUSIONS

These findings provide the molecular basis of binary EGFR/DNA targeting and uncover the oral bioavailability, blood-brain barrier permeability, and antitumor activity of ZR2002 supporting potential evaluation of this first-in-class drug in recurrent GBM.

A novel role for NFIA in restoring radiosensitivity in radioresistant NSCLC cells by downregulating the AKT and ERK pathways

Radioresistance remains the most challenging issue leading to radiotherapy failure in the treatment of non-small cell lung cancer (NSCLC). The nuclear factor IA (NFIA) is associated with tumor response to treatments in many cancers, but its role in NSCLC radioresistance remains unclear. Here, we established two radioresistant NSCLC cell lines, H226R and H460R, by dose-gradient irradiation to investigate the function of NFIA in NSCLC radioresistance. The results showed a dramatically reduced expression of NFIA in radioresistant cells accompanied with elevated phosphorylation of AKT and ERK, when compared with their parental cells. Overexpression of NFIA restored the sensitivity of radioresistant cells to radiation through increased ionizing radiation (IR)-induced apoptosis and DNA damage by downregulating p-AKT and p-ERK, whereas knockdown of NFIA promoted radioresistance of the parental cells. Our findings suggested that NFIA enhanced cell radiosensitivity by downregulating p-AKT and p-ERK in NSCLC. Our study fills a gap in the field of NFIA and radioresistance, and establishes a mechanistic foundation to improve radiotherapy efficiency in NSCLC patients.

Biological Rationale for Targeting MEK/ERK Pathways in Anti-Cancer Therapy and to Potentiate Tumour Responses to Radiation

ERK1 and ERK2 (ERKs), two extracellular regulated kinases (ERK1/2), are evolutionary-conserved and ubiquitous serine-threonine kinases involved in regulating cell signalling in normal and pathological tissues. The expression levels of these kinases are almost always different, with ERK2 being the more prominent. ERK1/2 activation is fundamental for the development and progression of cancer. Since their discovery, much research has been dedicated to their role in mitogen-activated protein kinases (MAPK) pathway signalling and in their activation by mitogens and mutated RAF or RAS in cancer cells. In order to gain a better understanding of the role of ERK1/2 in MAPK pathway signalling, many studies have been aimed at characterizing ERK1/2 splicing isoforms, mutants, substrates and partners. In this review, we highlight the differences between ERK1 and ERK2 without completely discarding the hypothesis that ERK1 and ERK2 exhibit functional redundancy. The main goal of this review is to shed light on the role of ERK1/2 in targeted therapy and radiotherapy and highlight the importance of identifying ERK inhibitors that may overcome acquired resistance. This is a highly relevant therapeutic issue that needs to be addressed to combat tumours that rely on constitutively active RAF and RAS mutants and the MAPK pathway.

Rescue Effect Inherited in Colony Formation Assays Affects Radiation Response

It is well known that nonirradiated cells can exhibit radiation damage (bystander effect), and recent findings have shown that nonirradiated cells may help protect irradiated cells (rescue effect). These findings call into question the traditional view of radiation response: cells cannot be envisioned as isolated units. Here, we investigated traditional colony formation assays to determine if they also comprise cellular communication affecting the radiation response, using colony formation assays with varying numbers of cells, modulated beam irradiation and media transfer. Our findings showed that surviving fraction gradually increased with increasing number of irradiated cells. Specifically, for DU-145 human prostate cancer cells, surviving fraction increased 1.9-to-4.1-fold after 5-12 Gy irradiation; and for MM576 human melanoma cells, surviving fraction increased 1.9-fold after 5 Gy irradiation. Furthermore, increased surviving fraction was evident after modulated beam irradiation, where irradiated cells could communicate with nonirradiated cells. Media from dense cell culture also increased surviving fraction. The results suggest that traditional colony formation assays comprise unavoidable cellular communication affecting radiation outcome and the shape of the survival curve. We also propose that the increased in-field surviving fraction after modulated beam irradiation is due to the same effect.

Radiotherapy modulates expression of EGFR, ERCC1 and p53 in cervical cancer

Cervical cancer is a public health problem and the molecular mechanisms underlying radioresistance are still poorly understood. Here, we evaluated the modulation of key molecules involved in cell proliferation, cell cycle and DNA repair in cervical cancer cell lines (CASKI and C33A) and in malignant tissues biopsied from 10 patients before and after radiotherapy. The expression patterns of epidermal growth factor receptor (EGFR), excision repair cross-complementation group 1 (ERCC1) and p53 were evaluated in cancer cell lines by quantitative PCR and western blotting, and in human malignant tissues by immunohistochemistry. The mutation status of TP53 gene was evaluated by direct sequencing. Among cell lines, absent or weak modulations of EGFR, ERCC1 and p53 were observed after exposure to 1.8 Gy. Conversely, increased expressions of p53 (5/10 patients; P=0.0239), ERCC1 (5/10 patients; P=0.0294) and EGFR (4/10 patients; P=0.1773) were observed in malignant tissues after radiotherapy with the same radiation dose. TP53 mutations were found only in one patient. Here we show that a single dose of radiotherapy induced EGFR, ERCC1 and p53 expression in malignant tissues from cervical cancer patients but not in cancer cell lines, highlighting the gap between in vitro and in vivo experimental models. Studies on larger patient cohorts are needed to allow an interpretation that an upregulation of p53, EGFR and ERCC1 may be part of a radioresistance mechanism.

Not breathing is not an option: How to deal with oxidative DNA damage

Oxidative DNA damage constitutes a major threat to genetic integrity, and has thus been implicated in the pathogenesis of a wide variety of diseases, including cancer and neurodegeneration. 7,8-dihydro-8oxo-deoxyGuanine (8-oxo-G) is one of the best characterised oxidative DNA lesions, and it can give rise to point mutations due to its miscoding potential that instructs most DNA polymerases (Pols) to preferentially insert Adenine (A) opposite 8-oxo-G instead of the correct Cytosine (C). If uncorrected, A:8-oxo-G mispairs can give rise to C:G→A:T transversion mutations. Cells have evolved a variety of pathways to mitigate the mutational potential of 8-oxo-G that include i) mechanisms to avoid incorporation of oxidized nucleotides into DNA through nucleotide pool sanitisation enzymes (by MTH1, MTH2, MTH3 and NUDT5), ii) base excision repair (BER) of 8-oxo-G in DNA (involving MUTYH, OGG1, Pol λ, and other components of the BER machinery), and iii) faithful bypass of 8-oxo-G lesions during replication (using a switch between replicative Pols and Pol λ). In the following, the fate of 8-oxo-G in mammalian cells is reviewed in detail. The differential origins of 8-oxo-G in DNA and its consequences for genetic stability will be covered. This will be followed by a thorough discussion of the different mechanisms in place to cope with 8-oxo-G with an emphasis on Pol λ-mediated correct bypass of 8-oxo-G during MUTYH-initiated BER as well as replication across 8-oxo-G. Furthermore, the multitude of mechanisms in place to regulate key proteins involved in 8-oxo-G repair will be reviewed. Novel functions of 8-oxo-G as an epigenetic-like regulator and insights into the repair of 8-oxo-G within the cellular context will be touched upon. Finally, a discussion will outline the relevance of 8-oxo-G and the proteins involved in dealing with 8-oxo-G to human diseases with a special emphasis on cancer.

Increased ERCC1 expression is linked to chromosomal aberrations and adverse tumor biology in prostate cancer

BACKGROUND

Animal model experiments have suggested a role of the DNA repair protein ERCC1 (Excision Repair Cross-Complementation Group 1) in prostate cancer progression.

METHODS

To better understand the impact of ERCC1 protein expression in human prostate cancer, a preexisting tissue microarray (TMA) containing more than 12,000 prostate cancer specimens was analyzed by immunohistochemistry and data were compared with tumor phenotype, PSA recurrence and several of the most common genomic alterations (TMPRSS2:ERG fusions: deletions of PTEN, 6q, 5q, 3p).

RESULTS

ERCC1 staining was seen in 64.7% of 10,436 interpretable tissues and was considered weak in 37.1%, moderate in 22.6% and strong in 5% of tumors. High-level ERCC1 staining was linked to advanced pT stage, high Gleason grade, positive lymph nodes, high pre-operative serum PSA, and positive surgical margin status (p < 0.0001 each). High ERCC1 expression was strongly associated with an elevated risk of PSA recurrence (p < 0.0001). This was independent of established prognostic features. A subgroup analysis of cancers defined by comparable quantitative Gleason grades revealed that the prognostic impact was mostly driven by low-grade tumors with a Gleason 3 + 3 or 3 + 4 (Gleason 4: ≤5%). High ERCC1 expression was strongly associated with the presence of genomic alterations and expression levels increased with the number of deletions present in the tumor. These latter data suggest a functional relationship of ERCC1 expression with genomic instability.

CONCLUSION

The results of our study demonstrate that expression of ERCC1 - a potential surrogate for genomic instability - is an independent prognostic marker in prostate cancer with particular importance in low-grade tumors.

A phase I clinical trial of binimetinib in combination with FOLFOX in patients with advanced metastatic colorectal cancer who failed prior standard therapy

Background

This was a first in-human, open-label, dose-escalation phase I study conducted to evaluate the maximum tolerated dose (MTD), safety, and efficacy of the combination of oral binimetinib and FOLFOX.

Materials and Methods

Patients with metastatic colorectal cancer (mCRC) who progressed on prior standard therapies received twice daily binimetinib continuously or intermittently with FOLFOX. Dose-limiting toxicities (DLTs) were assessed in the first 2 cycles of study treatment. Pharmacokinetic (PK) analysis of 5-FU and oxaliplatin was performed at the MTD in an expanded 6 patient cohort.

Results

Twenty-six patients were enrolled and assessed for safety. In the dose-escalation phase, no DLTs were noted in all binimetinib dosing schedules and the MTD of binimetinib in with FOLFOX was 45 mg orally twice daily. There were no significant differences in the PKs of 5-FU or oxaliplatin with or without binimetinib. Continuous dosing of binimetinib produced SD at 2 months in 9 of 13 evaluable patients and a median PFS of 3.5 months. Nine of 10 patients had PD at 2 months on the intermittent arm.

Conclusions

Oral binimetinib and FOLFOX has a manageable toxicity profile and showed some evidence of antitumor activity in heavily pretreated mCRC patients.

CAF-secreted CXCL1 conferred radioresistance by regulating DNA damage response in a ROS-dependent manner in esophageal squamous cell carcinoma

Five-year survival rate of esophageal squamous cell carcinoma (ESCC) patients treated with radiotherapy is <20%. Our study aimed to investigate whether cancer-associated fibroblasts (CAFs), one major component of tumor microenvironment, were involved in tumor radioresistance in ESCC. By use of human chemokine/cytokine array, human chemokine CXCL1 was found to be highly expressed in CAFs compared with that in matched normal fibroblasts. Inhibition of CXCL1 expression in CAFs significantly reversed CAF-conferred radioresistance in vitro and in vivo. CAF-secreted CXCL1 inhibited the expression of reactive oxygen species (ROS)-scavenging enzyme superoxide dismutase 1, leading to increased ROS accumulation following radiation, by which DNA damage repair was enhanced and the radioresistance was mediated. CAF-secreted CXCL1 mediated the radioresistance also by activation of Mek/Erk pathway. The cross talk of CAFs and ESCC cells induced CXCL1 expression in an autocrine/paracrine signaling loop, which further enhanced tumor radioresistance. Together, our study highlighted CAF-secreted CXCL1 as an attractive target to reverse tumor radioresistance and can be used as an independent prognostic factor of ESCC patients treated with chemoradiotherapy.

Cross-reacting material 197, a heparin-binding EGF-like growth factor inhibitor, reverses the chemoresistance in human cisplatin-resistant ovarian cancer

Cross-reacting material 197 (CRM197), a specific HB-EGF inhibitor, has been proven to be a promising antitumor agent for ovarian cancer therapy. Our previous studies have shown that CRM197 has potent antitumor activity in human cisplatin-resistant ovarian cancer. However, the relationship between CRM197 and the resistance to cisplatin remains unclear. Here, we report that CRM197 significantly reverses the resistance to cisplatin in cisplatin-resistant ovarian carcinoma cell line (A2780/CDDP). We established xenograft nude mice models with A2780 and A2780/CDDP cells. Notably, we observed that CRM197 suppresses the expression of HB-EGF and epidermal growth factor receptor in A2780/CDDP cells and xenografts harboring the overexpression of HB-EGF and epidermal growth factor receptor. Experiments conducted in vitro and in vivo suggest that CRM197 markedly downregulates the expression of excision repair cross-complementing group 1 (P = 0.002) and DNA repair capacity in A2780/CDDP tumor (P < 0.001) by inactivation of extracellular signal-regulated kinase signaling, providing novel possible mechanisms for the ability of CRM197 to restore drug sensitivity. These results suggest that CRM197 as an HB-EGF inhibitor might be a cisplatin-chemosensitizing agent for the treatment of ovarian carcinoma with resistance to cisplatin.

Radiation-Induced Esophagitis In Vivo and In Vitro Reveals That Epidermal Growth Factor Is a Potential Candidate for Therapeutic Intervention Strategy

PURPOSE

To establish and characterize radiation-induced esophagitis (RIE) in vivo and in vitro.

METHODS AND MATERIALS

Fractionated thoracic irradiation at 0, 8, 12, or 15 Gy was given daily for 5 days to Balb/c or C57Bl/6 mice. Changes in body weight gain and daily food intake were assessed. At the end of the study, we removed the esophagus and examined histology by hematoxylin and eosin staining, immune cell infiltration and apoptosis by fluorescence-activated cell sorting, and gene expression changes by quantitative real-time polymerase chain reaction. Het-1A human esophageal epithelial cells were irradiated at 6 Gy, treated with recombinant human growth factors, and examined for gene expression changes, apoptosis, proliferation, and signal transduction pathways.

RESULTS

We observed that irradiation at 12 Gy or 15 Gy per fraction produced significant reduction in body weight and decreased food intake in Balb/c mice but not as much in C57Bl/6 mice. Further analyses of Balb/c mice irradiated at 12 Gy/fraction revealed attenuated epithelium, inflamed mucosa, and increased numbers of infiltrating CD4+ helper T cells and apoptotic cells. Moreover, we found that expression of tissue inhibitor for metalloproteinase-1, plasminogen activator inhibitor-1, granulocyte macrophage-colony stimulating factor, vascular endothelial growth factor, and stromal-derived factor-1 were increased, whereas epidermal growth factor (EGF) was decreased. Irradiated Het-1A cells similarly showed a significant decrease in expression of EGF and connective tissue growth factor (CTGF). Treatment of EGF but not CTGF partially protected Het-1A cells from radiation-induced apoptosis and revealed phosphorylation of EGFR, AKT, and ERK signaling pathways.

CONCLUSIONS

We established a mouse model of RIE in Balb/c mice with 12 Gy × 5 fractions, which showed reduced body weight gain, food intake, and histopathologic features similar to those of human esophagitis. Decreased EGF expression in the irradiated esophagus suggests that EGF may be a potential therapeutic intervention strategy to treat RIE.

Radioprotective Agents: Strategies and Translational Advances

Radioprotectors are agents required to protect biological system exposed to radiation, either naturally or through radiation leakage, and they protect normal cells from radiation injury in cancer patients undergoing radiotherapy. It is imperative to study radioprotectors and their mechanism of action comprehensively, looking at their potential therapeutic applications. This review intimately chronicles the rich intellectual, pharmacological story of natural and synthetic radioprotectors. A continuous effort is going on by researchers to develop clinically promising radioprotective agents. In this article, for the first time we have discussed the impact of radioprotectors on different signaling pathways in cells, which will create a basis for scientific community working in this area to develop novel molecules with better therapeutic efficacy. The bright future of exceptionally noncytotoxic derivatives of bisbenzimidazoles is also described as radiomodulators. Amifostine, an effective radioprotectant, has been approved by the FDA for limited clinical use. However, due to its adverse side effects, it is not routinely used clinically. Recently, CBLB502 and several analog of a peptide are under clinical trial and showed high success against radiotherapy in cancer. This article reviews the different types of radioprotective agents with emphasis on the strategies for the development of novel radioprotectors for drug development. In addition, direction for future strategies relevant to the development of radioprotectors is also addressed.

Cellular Pathways in Response to Ionizing Radiation and Their Targetability for Tumor Radiosensitization

During the last few decades, improvements in the planning and application of radiotherapy in combination with surgery and chemotherapy resulted in increased survival rates of tumor patients. However, the success of radiotherapy is impaired by two reasons: firstly, the radioresistance of tumor cells and, secondly, the radiation-induced damage of normal tissue cells located in the field of ionizing radiation. These limitations demand the development of drugs for either radiosensitization of tumor cells or radioprotection of normal tissue cells. In order to identify potential targets, a detailed understanding of the cellular pathways involved in radiation response is an absolute requirement. This review describes the most important pathways of radioresponse and several key target proteins for radiosensitization.

DNA damage induces GDNF secretion in the tumor microenvironment with paracrine effects promoting prostate cancer treatment resistance

Though metastatic cancers often initially respond to genotoxic therapeutics, acquired resistance is common. In addition to cytotoxic effects on tumor cells, DNA damaging agents such as ionizing radiation and chemotherapy induce injury in benign cells of the tumor microenvironment resulting in the production of paracrine-acting factors capable of promoting tumor resistance phenotypes. In studies designed to characterize the responses of prostate and bone stromal cells to genotoxic stress, we found that transcripts encoding glial cell line-derived neurotrophic factor (GDNF) increased several fold following exposures to cytotoxic agents including radiation, the topoisomerase inhibitor mitoxantrone and the microtubule poison docetaxel. Fibroblast GDNF exerted paracrine effects toward prostate cancer cells resulting in enhanced tumor cell proliferation and invasion, and these effects were concordant with the expression of known GDNF receptors GFRA1 and RET. Exposure to GDNF also induced tumor cell resistance to mitoxantrone and docetaxel chemotherapy. Together, these findings support an important role for tumor microenvironment damage responses in modulating treatment resistance and identify the GDNF signaling pathway as a potential target for improving responses to conventional genotoxic therapeutics.

Localization and distribution of neurons that co-express xeroderma pigmentosum-A and epidermal growth factor receptor within Rosenthal's canal

Xeroderma pigmentosum-A (XPA) is a C4-type zinc-finger scaffolding protein that regulates the removal of bulky-helix distorting DNA damage products from the genome. Phosphorylation of serine residues within the XPA protein is associated with improved protection of genomic DNA and cell death resistance. Therefore, kinase signaling is one important mechanism for regulating the protective function of XPA. Previous experiments have shown that spiral ganglion neurons (SGNs) may mobilize XPA as a general stress response to chemical and physical ototoxicants. Therapeutic optimization of XPA via kinase signaling could serve as a means to improve DNA repair capacity within neurons following injury. The kinase signaling activity of the epidermal growth factor receptor (EGFR) has been shown in tumor cell lines to increase the repair of DNA damage products that are primarily repaired by XPA. Such observations suggest that EGFR may regulate the protective function of XPA. However, it is not known whether SGNs in particular or neurons in general could co-express XPA and EGFR. In the current study gene and protein expression of XPA and EGFR were determined from cochlear homogenates. Immunofluorescence assays were then employed to localize neurons expressing both EGFR and XPA within the ganglion. This work was then confirmed with double-immunohistochemistry. Rosenthal's canal served as the reference space in these experiments and design-based stereology was employed in first-order stereology quantification of immunoreactive neurons. The results confirmed that a population of SGNs that constitutively express XPA may also express the EGFR. These results provide the basis for future experiments designed to therapeutically manipulate the EGFR in order to regulate XPA activity and restore gene function in neurons following DNA damage.

Resveratrol Enhances Etoposide-Induced Cytotoxicity through Down-Regulating ERK1/2 and AKT-Mediated X-ray Repair Cross-Complement Group 1 (XRCC1) Protein Expression in Human Non-Small-Cell Lung Cancer Cells

Etoposide (VP-16), a topoisomerase II inhibitor, is an effective anti-cancer drug used for the treatment of non-small-cell lung cancer (NSCLC). Resveratrol is a naturally occurring polyphenolic compound that has been proved to have anti-cancer activity. XRCC1 is an important scaffold protein involved in base excision repair that is regulated by ERK1/2 and AKT signals and plays an important role in the development of lung cancer. However, the role of ERK1/2 and AKT-mediated XRCC1 expression in etoposide treatment alone or combined with resveratrol-induced cytotoxicity in NSCLC cells has not been identified. In this study, etoposide treatment increased XRCC1 mRNA and protein expression through AKT and ERK1/2 activation in two NSCLC cells, H1703 and H1975. Knockdown of XRCC1 in NSCLC cells by transfection of XRCC1 siRNA or inactivation of ERK1/2 and AKT resulted in enhancing cytotoxicity and cell growth inhibition induced by etoposide. Resveratrol inhibited the expression of XRCC1 and enhanced the etoposide-induced cell death and anti-proliferation effect in NSCLC cells. Furthermore, transfection with constitutive active MKK1 or AKT vectors could rescue the XRCC1 protein level and also the cell survival suppressed by co-treatment with etoposide and resveratrol. These findings suggested that down-regulation of XRCC1 expression by resveratrol can enhance the chemosensitivity of etoposide in NSCLC cells.

Treatment effect of buparlisib, cetuximab and irradiation in wild-type or PI3KCA-mutated head and neck cancer cell lines

Introduction In complement to anti-EGFR therapy, the targeting of PI3K/AKT/mTOR signaling pathway is of particular interest in the management of Head and Neck Squamous Cell Carcinoma (HNSCC). Here, we assess the effects of PI3K inhibition combined with anti-EGFR monoclonal antibody cetuximab and/or irradiation (RT). Material and methods Anti-proliferative effects of the combination of buparlisib (a specific PI3K inhibitor), cetuximab and RT was determined in two HNSCC cell lines (CAL33, PI3KCA H1047R-mutated and CAL27, PI3KCA wild-type). We examined biochemical factors related to proliferation, apoptosis (caspases), DNA repair (ERCC1, XRCC1) and the PI3K pathway (pEGFR/EGFR, pAKT/AKT, p-p70, p4EBP1). Results The best synergistic combined treatment in inhibiting cell proliferation was sequence 2 (cetuximab followed by buparlisib) in both cell lines. Addition of RT increased sequence 2 anti-proliferative effect only in CAL27. Data on protein expression indicated a possible activation of mTORC2 complex and caspases proteins in CAL27 not seen in CAL33. In CAL33, the synergistic anti-proliferative effect of the two drugs may derive from the higher sensitivity of mutated cells to PI3K targeting. Conclusions Our study demonstrates a synergistic effect of cetuximab followed by buparlisib in both PI3KCA wild-type and mutated cells, even with different intracellular signaling cross-talk depending on mutational status.

ERCC1 Induction after Oxaliplatin Exposure May Depend on KRAS Mutational Status in Colorectal Cancer Cell Line: In Vitro Veritas

Introduction: Oxaliplatin (Oxa) is widely used in metastatic colorectal cancer (mCRC), but currently there are not valid predictors of response to this drug. In the control arms both of OPUS and PRIME studies Oxa seems more active in patients with mCRC with mutated (mt) KRAS than in those with wild type (wt) KRAS. Recently we have retrospectively confirmed this suggestion, therefore we have hypothesized that the mutational status of KRAS could influence the expression of ERCC1, one of the main mechanisms of Oxa resistance.

Material and Methods: We used four cell lines of colorectal cancer: two KRAS wild type (wt) (HCT-8 and HT-29) and two KRAS mt (SW620 and SW480). We evaluated the sensitivity of these cell lines to Oxa by MTT-test as well the ERCC1 levels before and after 24 h exposure to Oxa by Real-Time PCR. We silenced KRAS in a KRAS mt cell line (SW620LV) to evaluate the impact on Oxa sensitivity and ERCC1 levels. Lastly, ERCC1 was also silenced in order to confirm the importance of this protein as an Oxa resistance factor.

Results: The KRAS mt cell lines resulted more sensitive to Oxa (OR 2.68; IC 95% 1.511-4.757 p<0.001). The basal levels of ERCC1 did not show significant differences between KRAS mt and wt cell lines, however, after 24 h exposure to Oxa, only the wt KRAS lines showed the ability to induce ERCC1, with a statistically significant difference (OR 42.9 IC 95% 17.260-106.972 p<0.0005). By silencing KRAS, sensitivity to Oxa was reduced in mt KRAS cell lines and this effect was associated with the acquisition of ability to induce ERCC1. Silencing of ERCC1, in turn, enhanced the sensitivity to Oxa in wt KRAS cell lines and restored sensitivity to Oxa in SW620LV cell line.

Conclusion: KRAS mutated cell lines were more sensitive to Oxa. This feature seems secondary to the inability of these cells to induce ERCC1 after exposure to Oxa. Thus, KRAS mutational status might be a predictor of response to Oxa in CRC surrogating the cell ability to induce ERCC1.

Radiation-induced signaling pathways that promote cancer cell survival (review)

Radiation therapy is a staple cancer treatment approach that has significantly improved local disease control and the overall survival of cancer patients. However, its efficacy is still limited by the development of radiation resistance and the presence of residual disease after therapy that leads to cancer recurrence. Radiation impedes cancer cell growth by inducing cytotoxicity, mainly caused by DNA damage. However, radiation can also simultaneously induce multiple pro-survival signaling pathways, such as those mediated by AKT, ERK and ATM/ATR, which can lead to suppression of apoptosis, induction of cell cycle arrest and/or initiation of DNA repair. These signaling pathways act conjointly to reduce the magnitude of radiation-induced cytotoxicity and promote the development of radioresistance in cancer cells. Thus, targeting these pro-survival pathways has great potential for the radiosensitization of cancer cells. In the present review, we summarize the current literature on how these radiation‑activated signaling pathways promote cancer cell survival.

Mig6 haploinsufficiency protects mice against streptozotocin-induced diabetes

AIMS/HYPOTHESIS

EGF and gastrin co-administration reverses type 1 diabetes in rodent models. However, the failure of this to translate into a clinical treatment suggests that EGF-mediated tissue repair is a complicated process and warrants further investigation. Thus, we aimed to determine whether EGF receptor (EGFR) feedback inhibition by mitogen-inducible gene 6 protein (MIG6) limits the effectiveness of EGF therapy and promotes type 1 diabetes development.

METHODS

We treated Mig6 (also known as Errfi1) haploinsufficient mice (Mig6 (+/-)) and their wild-type littermates (Mig6 (+/+)) with multiple low doses of streptozotocin (STZ), and monitored diabetes development via glucose homeostasis tests and histological analyses. We also investigated MIG6-mediated cytokine-induced desensitisation of EGFR signalling and the DNA damage repair response in 832/13 INS-1 beta cells.

RESULTS

Whereas STZ-treated Mig6 (+/+) mice became diabetic, STZ-treated Mig6 (+/-) mice remained glucose tolerant. In addition, STZ-treated Mig6 (+/-) mice exhibited preserved circulating insulin levels following a glucose challenge. As insulin sensitivity was similar between Mig6 (+/-) and Mig6 (+/+) mice, the preserved glucose tolerance in STZ-treated Mig6 (+/-) mice probably results from preserved beta cell function. This is supported by elevated Pdx1 and Irs2 mRNA levels in islets isolated from STZ-treated Mig6 (+/-) mice. Conversely, MIG6 overexpression in isolated islets compromises glucose-stimulated insulin secretion. Studies in 832/13 cells suggested that cytokine-induced MIG6 hinders EGFR activation and inhibits DNA damage repair. STZ-treated Mig6 (+/-) mice also have increased beta cell mass recovery.

CONCLUSIONS/INTERPRETATION

Reducing Mig6 expression promotes beta cell repair and abates the development of experimental diabetes, suggesting that MIG6 may be a novel therapeutic target for preserving beta cells.

Doubling down on the PI3K-AKT-mTOR pathway enhances the antitumor efficacy of PARP inhibitor in triple negative breast cancer model beyond BRCA-ness

Phosphoinositide 3-kinase (PI3K) pathway, in addition to its pro-proliferative and antiapoptotic effects on tumor cells, contributes to DNA damage repair (DDR). We hypothesized that GDC-0980, a dual PI3K-mammalian target of rapamycin (mTOR) inhibitor, would induce an efficient antitumor effect in BRCA-competent triple negative breast cancer (TNBC) model when combined with ABT888 and carboplatin. Mechanism-based in vitro studies demonstrated that GDC-0980 treatment alone or in combination led to DNA damage (increased pγH2AX(S139); Western blot, immunofluorescence), gain in poly ADP-ribose (PAR), and a subsequent sensitization of BRCA-competent TNBC cells to ABT888 plus carboplatin with a time-dependent 1) decrease in proliferation signals (pAKTT308/S473, pP70S6KT421/S424, pS6RPS235/236), PAR/poly(ADP-ribose) polymerase (PARP) ratios, PAR/pγH2AX ratios, live/dead cell ratios, cell cycle progression, and three-dimensional clonogenic growths and 2) increase in apoptosis markers (cleaved caspases 3 and 9, a pro-apoptotic BH3-only of Bcl-2 family (BIM), cleaved PARP, annexin V). The combination was effective in vitro in BRCA-wild-type PIK3CA-H1047R-mutated BT20 and PTEN-null HCC70 cells. The combination blocked the growth of established xenograft tumors by 80% to 90% with a concomitant decrease in tumor Ki67, CD31, phosphorylated vascular endothelial growth factor receptor, pS6RPS235/236, and p4EBP1T37/46 as well as an increase in cleaved caspase 3 immunohistochemistry (IHC) levels. Interestingly, a combination with GDC-0941, a pan-PI3K inhibitor, failed to block the tumor growth in MDA-MB231. Results demonstrate that the dual inhibition of PI3K and mTOR regulates DDR. In a BRCA-competent model, GDC-0980 enhanced the antitumor activity of ABT888 plus carboplatin by inhibiting both tumor cell proliferation and tumor-induced angiogenesis along with an increase in the tumor cell apoptosis. This is the first mechanism-based study to demonstrate the integral role of the PI3K-AKT-mTOR pathway in DDR-mediated antitumor action of PARP inhibitor in TNBC.

PARP and CHK inhibitors interact to cause DNA damage and cell death in mammary carcinoma cells

The present studies examined viability and DNA damage levels in mammary carcinoma cells following PARP1 and CHK1 inhibitor drug combination exposure. PARP1 inhibitors [AZD2281 ; ABT888 ; NU1025 ; AG014699] interacted with CHK1 inhibitors [UCN-01 ; AZD7762 ; LY2603618] to kill mammary carcinoma cells. PARP1 and CHK1 inhibitors interacted to increase both single strand and double strand DNA breaks that correlated with increased γH2AX phosphorylation. Treatment of cells with CHK1 inhibitors increased the phosphorylation of CHK1 and ERK1/2. Knock down of ATM suppressed the drug-induced increases in CHK1 and ERK1/2 phosphorylation and enhanced tumor cell killing by PARP1 and CHK1 inhibitors. Expression of dominant negative MEK1 enhanced drug-induced DNA damage whereas expression of activated MEK1 suppressed both the DNA damage response and tumor cell killing. Collectively our data demonstrate that PARP1 and CHK1 inhibitors interact to kill mammary carcinoma cells and that increased DNA damage is a surrogate marker for the response of cells to this drug combination.

The Molecular Crosstalk between the MET Receptor Tyrosine Kinase and the DNA Damage Response-Biological and Clinical Aspects

Radiation therapy remains an imperative treatment modality for numerous malignancies. Enduring significant technical achievements both on the levels of treatment planning and radiation delivery have led to improvements in local control of tumor growth and reduction in healthy tissue toxicity. Nevertheless, resistance mechanisms, which presumably also involve activation of DNA damage response signaling pathways that eventually may account for loco-regional relapse and consequent tumor progression, still remain a critical problem. Accumulating data suggest that signaling via growth factor receptor tyrosine kinases, which are aberrantly expressed in many tumors, may interfere with the cytotoxic impact of ionizing radiation via the direct activation of the DNA damage response, leading eventually to so-called tumor radioresistance. The aim of this review is to overview the current known data that support a molecular crosstalk between the hepatocyte growth factor receptor tyrosine kinase MET and the DNA damage response. Apart of extending well established concepts over MET biology beyond its function as a growth factor receptor, these observations directly relate to the role of its aberrant activity in resistance to DNA damaging agents, such as ionizing radiation, which are routinely used in cancer therapy and advocate tumor sensitization towards DNA damaging agents in combination with MET targeting.

Induction of apoptosis and suppression of ERCC1 expression by the potent amonafide analogue 8-c in human colorectal carcinoma cells

Previous studies have reported that 8-c [6-(2-(2-(dimethylamino)ethylamino)ethylamino)-2-octyl-1H-benzo[de]isoquinoline-1,3(2H)-dione], a novel amonafide analogue, was generated as a new anticancer candidate. However, little is known about its activity in chemoresistant cells. In this study, the antitumor effects of 8-c on the multi-drug-resistant human colorectal carcinoma cancer cell lines HCT-116/L-OHP and HCT-8/VCR have been investigated for the first time. 8-c showed similar concentration-dependent inhibitory activities against multi-drug-resistant cells and corresponding parental cell lines by the MTT assay after 48 h of treatment. 8-c treatment resulted in the induction of apoptosis, as evidenced by fluorescent staining analysis, comet assay data, and the increase in the number of apoptotic cells as detected by flow cytometry. Western blot, qPCR, and siRNA techniques were used to elucidate the molecular mechanism. Our study suggested that the apoptotic effect of 8-c can be attributed to the upregulation of p53, caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP) and the downregulation of Bcl-2. Furthermore, ERCC1 is essential for nucleotide excision repair. ERCC1 expression was correlated with sensitivity to chemotherapy in various colon cancer cell lines. It is intriguing that decreases in ERCC1 protein and mRNA levels were also observed in the HCT-116/L-OHP and HCT-8/VCR cells after exposure to 8-c. Further transient transfection of multi-drug-resistant cells with ERCC1 siRNA enhanced 8-c-induced cytotoxicity. In contrast, epidermal growth factor-induced increase in ERCC1 protein levels was shown to rescue cell viability upon 8-c treatment. These findings suggest that 8-c has a strong potential to be developed as a new antitumor agent for the treatment of multi-drug-resistant colon cancer cells, and is worthy of further studies.

Transcriptional regulation of human DNA repair genes following genotoxic stress: trigger mechanisms, inducible responses and genotoxic adaptation

DNA repair is the first barrier in the defense against genotoxic stress. In recent years, mechanisms that recognize DNA damage and activate DNA repair functions through transcriptional upregulation and post-translational modification were the focus of intensive research. Most DNA repair pathways are complex, involving many proteins working in discrete consecutive steps. Therefore, their balanced expression is important for avoiding erroneous repair that might result from excessive base removal and DNA cleavage. Amelioration of DNA repair requires both a fine-tuned system of lesion recognition and transcription factors that regulate repair genes in a balanced way. Transcriptional upregulation of DNA repair genes by genotoxic stress is counteracted by DNA damage that blocks transcription. Therefore, induction of DNA repair resulting in an adaptive response is only visible through a narrow window of dose. Here, we review transcriptional regulation of DNA repair genes in normal and cancer cells and describe mechanisms of promoter activation following genotoxic exposures through environmental carcinogens and anticancer drugs. The data available to date indicate that 25 DNA repair genes are subject to regulation following genotoxic stress in rodent and human cells, but for only a few of them, the data are solid as to the mechanism, homeostatic regulation and involvement in an adaptive response to genotoxic stress.

MicroRNA and signal transduction pathways in tumor radiation response

Tumor radiation response is an essential issue in radiotherapy and a core determining factor of tumor radioresistance or radiosensitivity. Multiple factors can influence tumor radiation response, and among them tumor genetic and epigenetic background, tumor microenvironment and tumor blood flow status may take a leading role. During the whole process of tumor radiation response, tumor radiosensitivity can be regulated in an orderly manner through some classical signal transduction pathways. Although these pathways have already owned multiple biological functions and involved in the process of carcinogenesis, their regulatory roles in tumor radiation response can not be ignored. MicroRNA (miRNA) is a class of non-coding RNA of about 22 nucleotides in length, which binds to the 3'-untranslated region (3'-UTR) of target gene and controls the expression of it at the post-transcriptional level. MiRNA participates in numerous physiology and pathology processes and acts as oncogene or tumor suppressor to affect cancer progression. Through interplaying with the key components in radiation related signal transduction pathways, miRNA could effectively activate the expression of DNA damage response genes and cell cycle related genes in the nucleus, and play a critical role in the modulation of radiation response and radiosensitivity in tumor cells. In this review, we mainly elucidate the regulatory mechanisms and functions of miRNA in these radiation related signal transduction pathways from three different aspects which include the upstream receptors, midstream transducer pathways, and downstream effector genes.

Metformin induces cytotoxicity by down-regulating thymidine phosphorylase and excision repair cross-complementation 1 expression in non-small cell lung cancer cells

Metformin is an antidiabetic drug recently shown to inhibit cancer cell proliferation and growth, although the involved molecular mechanisms have not been elucidated. In many cancer cells, high expression of thymidine phosphorylase (TP) and Excision repair cross-complementation 1 (ERCC1) is associated with poor prognosis. We used A549 and H1975 human non-small cell lung cancer (NSCLC) cell lines to investigate the role of TP and ERCC1 expression in metformin-induced cytotoxicity. Metformin treatment decreased cellular TP and ERCC1 protein and mRNA levels by down-regulating phosphorylated MEK1/2-ERK1/2 protein levels in a dose- and time-dependent manner. The enforced expression of the constitutively active MEK1 (MEK1-CA) vectors significantly restored cellular TP and ERCC1 protein levels and cell viability. Specific inhibition of TP and ERCC1 expression by siRNA enhanced the metformin-induced cytotoxicity and growth inhibition. Arachidin-1, an antioxidant stilbenoid, further decreased TP and ERCC1 expression and augmented metformin's cytotoxic effect, which was abrogated in lung cancer cells transfected with MEK1/2-CA expression vector. In conclusion, metformin induces cytotoxicity by down-regulating TP and ERCC1 expression in NSCLC cells.

The Concept of Divergent Targeting through the Activation and Inhibition of Receptors as a Novel Chemotherapeutic Strategy: Signaling Responses to Strong DNA-Reactive Combinatorial Mimicries

Recently, we reported the combination of multitargeted ErbB1 inhibitor-DNA damage combi-molecules with OCT in order to downregulate ErbB1 and activate SSTRs. Absence of translation to cell kill was believed to be partially due to insufficient ErbB1 blockage and DNA damage. In this study, we evaluated cell response to molecules that damage DNA more aggressively and induce stronger attenuation of ErbB1 phosphorylation. We used three cell lines expressing low levels (U87MG) or transfected to overexpress wildtype (U87/EGFR) or a variant (U87/EGFRvIII) of ErbB1. The results showed that Iressa ± HN2 and the combi-molecules, ZRBA4 and ZR2003, significantly blocked ErbB1 phosphorylation in U87MG cells. Addition of OCT significantly altered cell cycle distribution. Analysis of the DNA damage response pathway revealed strong upregulation of p53 by HN2 and the combi-molecules. Apoptosis was only induced by a 48 h exposure to HN2. All other treatments resulted in cell necrosis. This is in agreement with Akt-Bad pathway activation and survivin upregulation. Despite strong DNA damaging properties and downregulation of ErbB1 phosphorylation by these molecules, the strongest effect of SSTR activation was on cell cycle distribution. Therefore, any enhanced antiproliferative effects of combining ErbB1 inhibition with SSTR activation must be addressed in the context of cell cycle arrest.

Treatment of recurrent metastatic head and neck cancer: focus on cetuximab

EGFR belongs to the ErbB family of receptor tyrosine kinases and is associated with worse prognosis in head and neck squamous cell carcinoma (HNSCC). Cetuximab is a monoclonal antibody to the extracellular domain of EGFR and inhibits its downstream actions via multiple mechanisms. Besides its proven efficacy in locally advanced and incurable HNSCC, cetuximab has the distinct advantage of having a relatively tolerable side effect profile and not potentiating radiation toxicity. Though therapies for advanced HNSCC are evolving, locoregional recurrence and/or distant metastases occur in a large percentage of patients. Though some patients can be salvaged with surgery or radiation therapy, the majority are incurable, and are treated palliatively with systemic therapy. In the setting of first line therapy for recurrent/metastatic HNSCC, the EXTREME trial provided level 1 evidence that cetuximab improves overall survival when combined with cisplatinum and 5 FU. Following progression on first line chemotherapy, several phase II trials suggest that cetuximab monotherapy is a reasonable choice in this setting. Future studies should concentrate on clinical and molecular markers that may allow more personalized approaches to treating HNSCC, and combining EGFR inhibitors with other agents in a synergistic approach.

JWA deficiency suppresses dimethylbenz[a]anthracene-phorbol ester induced skin papillomas via inactivation of MAPK pathway in mice

Our previous studies indicated that JWA plays an important role in DNA damage repair, cell migration, and regulation of MAPKs. In this study, we investigated the role of JWA in chemical carcinogenesis using conditional JWA knockout (JWA^Δ2/Δ2) mice and two-stage model of skin carcinogenesis. Our results indicated that JWA^Δ2/Δ2 mice were resistant to the development of skin papillomas initiated by 7, 12-dimethylbenz(a)anthracene (DMBA) followed by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). In JWA^Δ2/Δ2 mice, the induction of papilloma was delayed, and the tumor number and size were reduced. In primary keratinocytes from JWA^Δ2/Δ2 mice, DMBA exposure induced more intensive DNA damage, while TPA-promoted cell proliferation was reduced. The further mechanistic studies showed that JWA deficiency blocked TPA-induced activation of MAPKs and its downstream transcription factor Elk1 both in vitro and in vivo. JWA^Δ2/Δ2 mice are resistance to tumorigenesis induced by DMBA/TPA probably through inhibition of transcription factor Elk1 via MAPKs. These results highlight the importance of JWA in skin homeostasis and in the process of skin tumor development.

Protein-intrinsic and signaling network-based sources of resistance to EGFR- and ErbB family-targeted therapies in head and neck cancer

Agents targeting EGFR and related ErbB family proteins are valuable therapies for the treatment of many cancers. For some tumor types, including squamous cell carcinomas of the head and neck (SCCHN), antibodies targeting EGFR were the first protein-directed agents to show clinical benefit, and remain a standard component of clinical strategies for management of the disease. Nevertheless, many patients display either intrinsic or acquired resistance to these drugs; hence, major research goals are to better understand the underlying causes of resistance, and to develop new therapeutic strategies that boost the impact of EGFR/ErbB inhibitors. In this review, we first summarize current standard use of EGFR inhibitors in the context of SCCHN, and described new agents targeting EGFR currently moving through pre-clinical and clinical development. We then discuss how changes in other transmembrane receptors, including IGF1R, c-Met, and TGF-β, can confer resistance to EGFR-targeted inhibitors, and discuss new agents targeting these proteins. Moving downstream, we discuss critical EGFR-dependent effectors, including PLC-γ; PI3K and PTEN; SHC, GRB2, and RAS and the STAT proteins, as factors in resistance to EGFR-directed inhibitors and as alternative targets of therapeutic inhibition. We summarize alternative sources of resistance among cellular changes that target EGFR itself, through regulation of ligand availability, post-translational modification of EGFR, availability of EGFR partners for hetero-dimerization and control of EGFR intracellular trafficking for recycling versus degradation. Finally, we discuss new strategies to identify effective therapeutic combinations involving EGFR-targeted inhibitors, in the context of new system level data becoming available for analysis of individual tumors.

Role and expression of FRS2 and FRS3 in prostate cancer

Background

FGF receptor substrates (FRS2 and FRS3) are key adaptor proteins that mediate FGF-FGFR signalling in benign as well as malignant tissue. Here we investigated FRS2 and FRS3 as a means of disrupting global FGF signalling in prostate cancer.

Methods

FRS2 and FRS3 manipulation was investigated in vitro using over-expression, knockdown and functional assays. FRS2 and FRS3 expression was profiled in cell lines and clinical tumors of different grades.

Results

In a panel of cell lines we observed ubiquitous FRS2 and FRS3 transcript and protein expression in both benign and malignant cells. We next tested functional redundancy of FRS2 and FRS3 in prostate cancer cells. In DU145 cells, specific FRS2 suppression inhibited FGF induced signalling. This effect was not apparent in cells stably over-expressing FRS3. Indeed FRS3 over-expression resulted in enhanced proliferation (p = 0.005) compared to control cells. Given this functional redundancy, we tested the therapeutic principle of dual targeting of FRS2 and FRS3 in prostate cancer. Co-suppression of FRS2 and FRS3 significantly inhibited ERK activation with a concomitant reduction in cell proliferation (p < 0.05), migration and invasion (p < 0.05). Synchronous knockdown of FRS2 and FRS3 with exposure to cytotoxic irradiation resulted in a significant reduction in prostate cancer cell survival compared to irradiation alone (p < 0.05). Importantly, this synergistic effect was not observed in benign cells. Finally, we investigated expression of FRS2 and FRS3 transcript in a cohort of micro-dissected tumors of different grades as well as by immunohistochemistry in clinical biopsies. Here, we did not observe any difference in expression between benign and malignant biopsies.

Conclusions

These results suggest functional overlap of FRS2 and FRS3 in mediating mitogenic FGF signalling in the prostate. FRS2 and FRS3 are not over-expressed in tumours but targeted dual inhibition may selectively adversely affect malignant but not benign prostate cells.

A Review of ERCC1 Gene in Bladder Cancer: Implications for Carcinogenesis and Resistance to Chemoradiotherapy

The excision repair cross-complementing group 1 (ERCC1) gene performs a critical incision step in DNA repair and is reported to be correlated with carcinogenesis and resistance to drug or ionizing radiation therapy. We reviewed the correlation between ERCC1 and bladder cancer. In carcinogenesis, several reports discussed the relation between ERCC1 single nucleotide polymorphisms and carcinogenesis in bladder cancer only in case-control studies. Regarding the relation between ERCC1 and resistance to chemoradiotherapy, in vitro and clinical studies indicate that ERCC1 might be related to resistance to radiation therapy rather than cisplatin therapy. It is controversial whether ERCC1 predicts prognosis of bladder cancer treated with cisplatin-based chemotherapy. Tyrosine kinase receptors or endothelial-mesenchymal transition are reported to regulate the expression of ERCC1, and further study is needed to clarify the mechanism of ERCC1 expression and resistance to chemoradiotherapy in vitro and to discover novel therapies for advanced and metastatic bladder cancer.

Inhibition of p42 MAPK using a nonviral vector-delivered siRNA potentiates the anti-tumor effect of metformin in prostate cancer cells

AIMS

The aim of this work was to study if a G1-polyamidoamine dendrimer/siRNA dendriplex can remove the p42 MAPK protein in prostate cancer cells and to potentiate the anti-tumoral effect of the antidiabetic drug metformin and taxane docetaxel.

MATERIAL & METHODS

The dendriplex uptake was studied using flow cytometry analysis. Transfection efficiency was determined by measuring p42 MAPK mRNA and protein levels. Anti-tumoral effects were determined by measuring cellular proliferation and damage.

RESULTS

The dendriplex siRNA/G1-polyamidoamine dendrimer decreased both p42 MAPK mRNA and protein levels by more than 80%, which potentiates the anti-tumoral effects of metformin.

CONCLUSION

Blockade of the MAPK pathway using a dendrimer-vehiculized siRNA to block the MAPK signaling pathway in prostate cancer cells can potentiate the anti-tumoral activity of anticancer drugs, indicating that the combination of siRNA-mediated blockade of survival signals plus anti-tumoral therapy might be a useful approach for cancer therapy.