Differential functions of Ras for malignant phenotypic conversion

Role of RAS signaling in ovarian cancer

The RAS family of proteins is among the most frequently mutated genes in human malignancies. In ovarian cancer (OC), the most lethal gynecological malignancy, RAS, especially KRAS mutational status at codons 12, 13, and 61, ranges from 6-65% spanning different histo-types. Normally RAS regulates several signaling pathways involved in a myriad of cellular signaling cascades mediating numerous cellular processes like cell proliferation, differentiation, invasion, and death. Aberrant activation of RAS leads to uncontrolled induction of several downstream signaling pathways such as RAF-1/MAPK (mitogen-activated protein kinase), PI3K phosphoinositide-3 kinase (PI3K)/AKT, RalGEFs, Rac/Rho, BRAF (v-Raf murine sarcoma viral oncogene homolog B), MEK1 (mitogen-activated protein kinase kinase 1), ERK (extracellular signal-regulated kinase), PKB (protein kinase B) and PKC (protein kinase C) involved in cell proliferation as well as maintenance pathways thereby driving tumorigenesis and cancer cell propagation. KRAS mutation is also known to be a biomarker for poor outcome and chemoresistance in OC. As a malignancy with several histotypes showing varying histopathological characteristics, we focus on reviewing recent literature showcasing the involvement of oncogenic RAS in mediating carcinogenesis and chemoresistance in OC and its subtypes.

Targeted and systemic insights into the crosstalk between DNA-dependent protein kinase catalytic subunit and receptors of estrogen, progesterone and epidermal growth factor in the context of cancer

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) has emerged as a regulator of carcinogenesis. Increased expression of DNA-PKcs correlates with metastatic cancers. Here we review recently reported crosstalk of DNA-PKcs with estrogen (ER), progesterone (PR) and epidermal growth factor (EGFR) receptors. The reports show an extensive network of functional and direct interactions. Targeted studies focused on specific molecular mechanisms, and a systems biology network analysis shows unbiasedly engagement of various cellular functions. Feedforward regulation between expression and activities of DNA-PKcs and ER, DNA-PKcs-dependent phosphorylation of PR and an impact on PR-dependent transcription, and DNA-PKcs-promoted EGFR-dependent aggressiveness and metastases are examples of the results of targeted studies. Systems biology approach extracted many more genes and proteins engaged by DNA-PKcs in interaction with ER, PR, and EGFR. Examples are such regulators and predictors of breast tumorigenesis as BRCA1, TP53, and 18 genes of the MammaPrint signature. Reviewed here data suggest that the diagnostic value of DNA-PKcs in the context of ER, PR and EGFR signaling is defined by a network signature rather than by single markers. This review summarizes mechanisms of DNA-PKcs interaction with ER, PR, and EGFR, highlights tumor suppressors and oncogenes engaged by DNA-PKcs, and emphasizes the importance of diagnostic network-based signatures.

Isolation and characterization of adult mammary stem cells from breast cancer-adjacent tissues

Normal adult mammary stem cells (AMSCs) are promising sources for breast reconstruction, particularly following the resection of breast tumors. However, carcinogenic events can potentially convert normal AMSCs to cancer stem cells, posing a safety concern for the use of AMSCs for clinical tissue regeneration. In the present study, AMSCs and autologous primary breast cancer cells were isolated and compared for their ability to differentiate, their gene expression profile, and their potential to form tumors in vivo. AMSCs were isolated from normal tissue surrounding primary breast tumors by immunomagnetic sorting. The pluripotency of these cells was investigated by differentiation analysis, and gene expression profiles were compared with microarrays. Differentially expressed candidate genes were confirmed by reverse transcription-polymerase chain reaction and western blot analyses. The in vivo tumorigenicity of these cells, compared with low-malignancy MCF-7 cells, was also investigated by xenograft tumor formation analysis. The results revealed that AMSCs isolated from normal tissues surrounding primary breast tumors were positive for the stem cell markers epithelial-specific antigen and keratin-19. When stimulated with basic fibroblast growth factor, a differentiation agent, these AMSCs formed lobuloalveolar structures with myoepithelia that were positive for common acute lymphoblastic leukemia antigen. The gene expression profiles revealed that, compared with cancer cells, AMSCs expressed low levels of oncogenes, including MYC, RAS and ErbB receptor tyrosine kinase 2, and high levels of tumor suppressor genes, including RB transcriptional corepressor 1, phosphatase and tensin homolog, and cyclin-dependent kinase inhibitor 2A. When injected into nude non-obese diabetic/severe combined immunodeficiency-type mice, the AMSCs did not form tumors, and regular mammary ductal structures were generated. The AMSCs isolated from normal tissue adjacent to primary breast tumors had the normal phenotype of mammary stem cells, and therefore may be promising candidates for mammary reconstruction subsequent to breast tumor resection.

RAS mutations in indeterminate thyroid nodules are predictive of the follicular variant of papillary thyroid carcinoma

OBJECTIVE

RAS mutations are the most common mutations in thyroid nodules with indeterminate cytology by fine-needle aspiration cytology (FNAC), and are mutually exclusive with BRAF mutations. However, the diagnostic utility of RAS mutation analysis is uncertain. We evaluated the diagnostic utility of RAS mutation analysis in indeterminate thyroid nodules.

DESIGN, PATIENTS, AND MEASUREMENTS

A total of 155 thyroid nodules (90 benign and 65 indeterminate) negative for BRAF(V) (600E) mutations on FNAC were analysed for mutations in RAS codon 61 using pyrosequencing methods. We evaluated diagnostic accuracy of RAS mutation for predicting thyroid malignancy based on the surgical pathologic diagnosis.

RESULTS

Among the 65 BRAF(V) (600E) -negative indeterminate thyroid nodules identified by FNAC, 25 (38·5%) exhibited point mutations in RAS 61 consisting of 18 NRAS 61 (72%), and 7 HRAS 61 (28%) mutations. In contrast, only five of 90 (5·6%) nodules with benign cytology had RAS mutations. Only two of 25 (8·0%) RAS 61(+) indeterminate nodules exhibited malignant ultrasonographic features. Of the 15 patients with RAS 61(+) -indeterminate nodules who underwent thyroid surgery, 14 (93·3%) were diagnosed as malignant, including 13 follicular variant of papillary thyroid carcinomas (FVPTC), and one follicular thyroid carcinoma (FTC). The average tumour size was 1·79 ± 0·62 cm. Multifocality was seen in 28·6% of cases, with 7·1% exhibiting extrathyroidal extension; no lymph node or distant metastases were evident. Based on the surgical pathologic diagnosis results, preoperative RAS 61 mutation analysis on FNAC exhibited 93·3% sensitivity, 75·0% specificity, 93·3% positive predictive value, 75·0% negative predictive value and 89·5% diagnostic accuracy for predicting malignancies.

CONCLUSION

Our results suggest that RAS mutation analysis holds great promise as a preoperative diagnostic tool for predicting FVPTC in cytologically and sonographically indeterminate nodules negative for BRAF mutations.

Role of molecular diagnostic markers in the management of indeterminate and suspicious thyroid nodules

Incidental thyroid nodules are commonly found during routine neck examination. Fine needle aspiration (FNA) followed by cytological examination is currently considered as the most reliable method for evaluation of thyroid nodules. However, 10–40% of FNA results are inconclusive, and are reported as indeterminate or suspicious. Approximately 20% of indeterminate or suspicious nodules are malignant. Therefore, there has been an increasing trend in use of molecular markers as an adjunctive measure for more accurate preoperative diagnosis of indeterminate or suspicious nodules. Molecular markers can be used alone or as a part of molecular panels. Although some investigations revealed promising findings regarding the potential use of molecular markers in the management of thyroid nodules, their true impact on management of patients with indeterminate nodules is still unclear.

The transcription factor FOXM1 (Forkhead box M1): proliferation-specific expression, transcription factor function, target genes, mouse models, and normal biological roles

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor, which stimulates cell proliferation and exhibits a proliferation-specific expression pattern. Accordingly, both the expression and the transcriptional activity of FOXM1 are increased by proliferation signals, but decreased by antiproliferation signals, including the positive and negative regulation by protooncoproteins or tumor suppressors, respectively. FOXM1 stimulates cell cycle progression by promoting the entry into S-phase and M-phase. Moreover, FOXM1 is required for proper execution of mitosis. Accordingly, FOXM1 regulates the expression of genes, whose products control G1/S-transition, S-phase progression, G2/M-transition, and M-phase progression. Additionally, FOXM1 target genes encode proteins with functions in the execution of DNA replication and mitosis. FOXM1 is a transcriptional activator with a forkhead domain as DNA binding domain and with a very strong acidic transactivation domain. However, wild-type FOXM1 is (almost) inactive because the transactivation domain is repressed by three inhibitory domains. Inactive FOXM1 can be converted into a very potent transactivator by activating signals, which release the transactivation domain from its inhibition by the inhibitory domains. FOXM1 is essential for embryonic development and the foxm1 knockout is embryonically lethal. In adults, FOXM1 is important for tissue repair after injury. FOXM1 prevents premature senescence and interferes with contact inhibition. FOXM1 plays a role for maintenance of stem cell pluripotency and for self-renewal capacity of stem cells. The functions of FOXM1 in prevention of polyploidy and aneuploidy and in homologous recombination repair of DNA-double-strand breaks suggest an importance of FOXM1 for the maintenance of genomic stability and chromosomal integrity.

RAS mutations in thyroid FNA specimens are highly predictive of predominantly low-risk follicular-pattern cancers

INTRODUCTION

RAS mutations are common in thyroid tumors and confer a high risk of cancer when detected in fine-needle aspiration (FNA) specimens. Specific characteristics of RAS-positive thyroid cancers are not well described.

METHODS

From April 2007 to April 2009, 921 consecutive patients undergoing FNA were evaluated prospectively with a panel of molecular markers. Ultrasonographic, cytological, histological, and surgical outcomes were retrospectively assessed.

RESULTS

Sixty-eight aspirates from 66 patients were positive for RAS mutations including 63 cytologically indeterminate (93%), 3 malignant (4%), and 2 benign (3%) specimens. Cancer was histologically confirmed in 52 of 63 aspirates (83%) including the following: 46 papillary thyroid cancers, 4 follicular thyroid cancers, 1 medullary cancer, and 1 anaplastic cancer. All 46 RAS-positive papillary thyroid cancers, including 1 metastatic cancer, had follicular variant histology papillary thyroid cancer; only 11 tumors demonstrated vascular/capsular invasion and 4 had infiltrative growth. Of 48 patients with differentiated thyroid cancer, lymph node metastasis was uncommon and bilateral cancer was present in 48%. Only 33% of malignant nodules were suspicious by preoperative ultrasonography. At a mean follow-up of 22 months, 31 of 35 differentiated thyroid cancer patients (89%) have no evidence of recurrence, 4 patients (9%) have detectable thyroglobulin, 1 patient has bone metastases, and both patients with medullary and anaplastic cancer have died.

CONCLUSION

Most RAS-positive thyroid cancers have indeterminate cytology, lack suspicious ultrasound features, and are histologically low-grade follicular variant histology papillary thyroid cancer. Lymph node and distant metastases are uncommon but bilateral disease is frequent. Total thyroidectomy should be considered for initial surgical management of most patients with RAS-positive FNA results. The role of prophylactic lymphadenectomy remains unclear.

RAS Mutations and Oncogenesis: Not all RAS Mutations are Created Equally

Mutation in RAS proteins is one of the most common genetic alterations observed in human and experimentally induced rodent cancers. In vivo, oncogenic mutations have been shown to occur at exons 12, 13, and 61, resulting in any 1 of 19 possible point mutations in a given tumor for a specific RAS isoform. While some studies have suggested a possible role of different mutant alleles in determining tumor severity and phenotype, no general consensus has emerged on the oncogenicity of different mutant alleles in tumor formation and progression. Part of this may be due to a lack of a single, signature pathway that shows significant alterations between different mutations. Rather, it is likely that subtle differences in the activation, or lack thereof, of downstream effectors by different RAS mutant alleles may determine the eventual outcome in terms of tumor phenotype. This paper reviews our current understanding of the potential role of different RAS mutations on tumorigenesis, highlights studies in model cell culture and in vivo systems, and discusses the potential of expression array and computational network modeling to dissect out differences in activated RAS genes in conferring a transforming phenotype.

RASOnD-a comprehensive resource and search tool for RAS superfamily oncogenes from various species

Background

The Ras superfamily plays an important role in the control of cell signalling and division. Mutations in the Ras genes convert them into active oncogenes. The Ras oncogenes form a major thrust of global cancer research as they are involved in the development and progression of tumors. This has resulted in the exponential growth of data on Ras superfamily across different public databases and in literature. However, no dedicated public resource is currently available for data mining and analysis on this family. The present database was developed to facilitate straightforward accession, retrieval and analysis of information available on Ras oncogenes from one particular site.

Description

We have developed the RAS Oncogene Database (RASOnD) as a comprehensive knowledgebase that provides integrated and curated information on a single platform for oncogenes of Ras superfamily. RASOnD encompasses exhaustive genomics and proteomics data existing across diverse publicly accessible databases. This resource presently includes overall 199,046 entries from 101 different species. It provides a search tool to generate information about their nucleotide and amino acid sequences, single nucleotide polymorphisms, chromosome positions, orthologies, motifs, structures, related pathways and associated diseases. We have implemented a number of user-friendly search interfaces and sequence analysis tools. At present the user can (i) browse the data (ii) search any field through a simple or advance search interface and (iii) perform a BLAST search and subsequently CLUSTALW multiple sequence alignment by selecting sequences of Ras oncogenes. The Generic gene browser, GBrowse, JMOL for structural visualization and TREEVIEW for phylograms have been integrated for clear perception of retrieved data. External links to related databases have been included in RASOnD.

Conclusions

This database is a resource and search tool dedicated to Ras oncogenes. It has utility to cancer biologists and cell molecular biologists as it is a ready source for research, identification and elucidation of the role of these oncogenes. The data generated can be used for understanding the relationship between the Ras oncogenes and their association with cancer. The database updated monthly is freely accessible online at http://202.141.47.181/rasond/ and http://www.aiims.edu/RAS.html.

Activation of H-Ras and Rac1 correlates with epidermal growth factor-induced invasion in Hs578T and MDA-MB-231 breast carcinoma cells

There is considerable experimental evidence that hyperactive Ras proteins promote breast cancer growth and development including invasiveness, despite the low frequency of mutated forms of Ras in breast cancer. We have previously shown that H-Ras, but not N-Ras, induces an invasive phenotype mediated by small GTPase Rac1 in MCF10A human breast epithelial cells. Epidermal growth factor (EGF) plays an important role in aberrant growth and metastasis formation of many tumor types including breast cancer. The present study aims to investigate the correlation between EGF-induced invasiveness and Ras activation in four widely used breast cancer cell lines. Upon EGF stimulation, invasive abilities and H-Ras activation were significantly increased in Hs578T and MDA-MB-231 cell lines, but not in MDA-MB-453 and T47D cell lines. Using small interfering RNA (siRNA) to target H-Ras, we showed a crucial role of H-Ras in the invasive phenotype induced by EGF in Hs578T and MDA-MB-231 cells. Moreover, siRNA-knockdown of Rac1 significantly inhibited the EGF-induced invasiveness in these cells. Taken together, this study characterized human breast cancer cell lines with regard to the relationship between H-Ras activation and the invasive phenotype induced by EGF. Our data demonstrate that the activation of H-Ras and the downstream molecule Rac1 correlates with EGF-induced breast cancer cell invasion, providing important information on the regulation of malignant progression in mammary carcinoma cells.

K-RAS mutation in the screening, prognosis and treatment of cancer

The potential use of K-RAS mutation as a cancer screening biomarker has been investigated for many years. Numerous associations between K-RAS mutation and various cancers have been established, but these associations have not been translated into effective, cost-efficient cancer screening strategies. This lack of progress may be due to the existence of K-RAS mutation in nontumor tissues and/or using detection, rather than quantitation, of K-RAS mutation as the endpoint for cancer risk categorization. K-RAS mutation appears to be a useful prognostic biomarker for colon cancer. Recent progress toward sensitive and quantitative mutation characterization and the successful use of K-RAS mutation in a personalized medicine approach to targeted biological therapy selection are likely to re-direct and expand the use of K-RAS mutation as a cancer biomarker in the near future.

Src signaling in cancer invasion

Src is a non-receptor cytoplasmic tyrosine kinase which becomes activated following the stimulation of plasma membrane receptors including receptor tyrosine kinases and integrins, and is an indispensable player of multiple physiological homeostatic pathways. Once activated, Src is the starting point for several biochemical cascades that thereby propagate signals generated extracellularly along intracellular interconnected transduction pathways. Src transmits signals promoting cell survival and mitogenesis and, in addition, exerts a profound effect on the reorganization of the cytoskeleton and the adhesion systems that underpin cell migration and invasion. Because increased activity of Src is a frequent occurrence in many types of human cancer, and because there is evidence of a prominent role of Src in invasion and in other tumor progression-related events such as epithelial-mesenchymal transition (EMT) and development of metastasis, inhibitors targeting Src are being viewed as promising drugs for cancer therapy.

Phenotype-assisted transcriptome analysis identifies FOXM1 downstream from Ras-MKK3-p38 to regulate in vitro cellular invasion

The Ras oncogene is known to activate three major MAPK pathways, ERK, JNK, p38 and exert distinct cellular phenotypes, that is, apoptosis and invasion through the Ras-MKK3-p38-signaling cascade. We attempted to identify the molecular targets of this pathway that selectively govern the invasive phenotype. Stable transfection of NIH3T3 fibroblasts with MKK3(act) cDNA construct revealed similar p38-dependent in vitro characteristics observed in Ha-Ras(EJ)-transformed NIH3T3 cells, including enhanced invasiveness and anchorage-independent growth correlating with p38 phosphorylation status. To identify the consensus downstream targets of the Ras-MKK3-p38 cascade involved in invasion, in vitro invasion assays were used to isolate highly invasive cells from both, MKK3 and Ha-Ras(EJ) transgenic cell lines. Subsequently a genome-wide transcriptome analysis was employed to investigate differentially regulated genes in invasive Ha-Ras(EJ)- and MKK3(act)-transfected NIH3T3 fibroblasts. Using this phenotype-assisted approach combined with system level protein-interaction network analysis, we identified FOXM1, PLK1 and CDK1 to be differentially regulated in invasive Ha-Ras(EJ)-NIH3T3 and MKK3(act)-NIH3T3 cells. Finally, a FOXM1 RNA-knockdown approach revealed its requirement for both invasion and anchorage-independent growth of Ha-Ras(EJ)- and MKK3(act)-NIH3T3 cells. Together, we identified FOXM1 as a key downstream target of Ras and MKK3-induced cellular in vitro invasion and anchorage-independent growth signaling.

Pathogenesis of lung cancer signalling pathways: roadmap for therapies

Lung cancer is the major cancer killer worldwide, and 5-yr survival is extremely poor (<or=15%), accentuating the need for more effective therapeutic strategies. Significant advances in lung cancer biology may lead to customised therapy based on targeting specific genes and pathways. The main signalling pathways that could provide roadmaps for therapy include the following: growth promoting pathways (Epidermal Growth Factor Receptor/Ras/PhosphatidylInositol 3-Kinase), growth inhibitory pathways (p53/Rb/P14(ARF), STK11), apoptotic pathways (Bcl-2/Bax/Fas/FasL), DNA repair and immortalisation genes. Epigenetic changes in lung cancer contribute strongly to cell transformation by modifying chromatin structures and the specific expression of genes; these include DNA methylation, histone and chromatin protein modification, and micro-RNA, all of which are responsible for the silencing of tumour suppressor genes while enhancing expression of oncogenes. The genetic and epigenetic pathways involved in lung tumorigenesis differ between smokers and nonsmokers, and are tools for cancer diagnosis, prognosis, clinical follow-up and targeted therapies.

The miR-18a* microRNA functions as a potential tumor suppressor by targeting on K-Ras

The Ras proto-oncogene mediates a wide variety of cellular events and is frequently mutated in cancer. MicroRNAs (miRNAs) may regulate the development of cancer through their effect on the target genes. In the search of miRNAs that target on Ras, miR-18a* is the first time confirmed to target on K-Ras and furthermore not on N- and H-Ras. miR-18a* repression by transfection with anti-miR-18a* inhibitor increased the K-Ras expression as well as the luciferase activity of a reporter construct containing the 3'-untranslated region of K-Ras messenger RNA. Furthermore, the miR-18a* repression also increased the cell proliferation and promoted the anchorage-independent growth in soft agar of human squamous carcinoma A431 cells, colon adenocarcinoma HT-29 cells and fetal hepatic WRL-68 cells. On the other hand, ectopic expression of miR-18a* by transfection with miR-18a* precursor suppressed K-Ras expression, cell proliferation and anchorage-independent growth of A431 cells. The increase in cell proliferation and anchorage-independent growth upon miR-18a* repression was, however, rendered by the Ras inhibitor farnesylthiosalicylic acid. In conclusion, miR-18a* may function as a tumor suppressor by targeting on K-Ras. Therefore, the miRNA may also be a potential therapeutic agent or target for cancer therapy.

Mouse breast cancer model-dependent changes in metabolic syndrome-associated phenotypes caused by maternal dioxin exposure and dietary fat

Diets high in fat are associated with increased susceptibility to obesity and metabolic syndrome. Increased adipose tissue that is caused by high-fat diets (HFD) results in altered storage of lipophilic toxicants like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which may further increase susceptibility to metabolic syndrome. Because both TCDD and HFD are associated with increased breast cancer risk, we examined their effects on metabolic syndrome-associated phenotypes in three mouse models of breast cancer: 7,12-dimethylbenz[a]anthracene (DMBA), Tg(MMTV-Neu)202Mul/J (HER2), and TgN(MMTV-PyMT)634Mul/J (PyMT), all on an FVB/N genetic background. Pregnant mice dosed with 1 microg/kg of TCDD or vehicle on gestational day 12.5 were placed on a HFD or low-fat diet (LFD) at parturition. Body weights, percent body fat, and fasting blood glucose were measured longitudinally, and triglycerides were measured at study termination. On HFD, all cancer models reached the pubertal growth spurt ahead of FVB controls. Among mice fed HFD, the HER2 model had a greater increase in body weight and adipose tissue from puberty through adulthood compared with the PyMT and DMBA models. However, the DMBA model consistently had higher fasting blood glucose levels than the PyMT and HER2 models. TCDD only impacted serum triglycerides in the PyMT model maintained on HFD. Because the estrogenic activity of the HFD was three times lower than that of the LFD, differential dietary estrogenic activities did not drive the observed phenotypic differences. Rather, the HFD-dependent changes were cancer model dependent. These results show that cancer models can have differential effects on metabolic syndrome-associated phenotypes even before cancers arise.

Targeting receptor tyrosine kinase signalling in small cell lung cancer (SCLC): what have we learned so far?

Small cell lung cancer (SCLC) is an aggressive form of lung cancer, which represents 13% of all cases and is strongly associated with cigarette smoking. The survival of SCLC patients is dismal and has not greatly improved in the last 20 years, despite advances in chemotherapy regimens and a better understanding of SCLC biology. The development of resistance to chemotherapy and metastasis are commonly recognized as important causes of poor clinical outcome in SCLC. Targeting receptor tyrosine kinase (RTK) signalling represents an attractive approach to develop new drugs for SCLC, in view of the accumulating data demonstrating that polypeptide growth factors play a key role in driving SCLC cell proliferation, chemoresistance and metastasis. The insulin-like growth factor-I receptor (IGF-IR), c-Kit, vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR) have been identified as potential drug targets in SCLC. Moreover, downstream signalling mediators of RTKs, such as phosphoinositide 3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) may also represent attractive candidate molecules for anti-cancer therapies in SCLC. Here we will review the available data concerning results with RTK inhibitors in SCLC and the clinical trials undertaken to investigate the potential of these compounds as anti-tumour agents in SCLC.

Activating Transcription Factor 2 Mediates Matrix Metalloproteinase-2 Transcriptional Activation Induced by p38 in Breast Epithelial Cells

Mounting evidence suggests a role for matrix metalloproteinase (MMP)-2 in the malignant progression of breast cancer cells. We showed previously that H-Ras, but not N-Ras, induced invasion of MCF10A human breast epithelial cells through Rac-MKK3/6-p38 pathway resulted in MMP-2 up-regulation. Activation of p38 pathway by MKK6 caused a selective up-regulation of MMP-2. In this study, we aimed to elucidate the transcriptional regulation of MMP-2 by p38 pathway leading to the invasive phenotype of MCF10A cells. By using 5' deletion mutant constructs of MMP-2 promoter, we showed that deletion of the region containing activator protein-1 (AP-1) site caused the greatest reduction of MMP-2 promoter activity both in MKK6- and H-Ras-activated MCF10A cells, suggesting that the AP-1 binding site is critical for the MMP-2 promoter activation. DNA binding and transcriptional activities of AP-1 were increased by MKK6 or H-Ras as evidenced by electrophoretic mobility shift assay and luciferase assay using an AP-1-driven plasmid. By doing immunoinhibition assay and chromatin immunoprecipitation assay, we revealed the activating transcription factor (ATF) 2 as a transcription factor for MMP-2 gene expression through binding to the functional AP-1 site. Activation of ATF2, which depended on p38 activity, was crucial for MMP-2 promoter activity as well as induction of invasive and migrative phenotypes in MCF10A cells. This is the first report revealing ATF2 as an essential transcription factor linking MKK3/6-p38 signaling pathway to MMP-2 up-regulation, providing evidence for a direct role of ATF2 activation in malignant phenotypic changes of human breast epithelial cells.

H-Ras selectively up-regulates MMP-9 and COX-2 through activation of ERK1/2 and NF-kappaB: an implication for invasive phenotype in rat liver epithelial cells

One of the most frequent events in carcinogenesis is uncontrolled activation of Ras signaling pathway. A previous study demonstrated that the introduction of H-Ras into the normal WB-F344 rat liver epithelial (WB) cell line and adult male F344 rats resulted in tumorigenicity. The present study investigated whether H-Ras induced the invasive and migrative phenotypes in WB cells, and subsequently aimed at characterizing the underlying mechanisms. H-Ras induced the invasive and migrative phenotypes of WB cells with a selective up-regulation of matrix metalloproteinase (MMP)-9, but not MMP-2. Cyclooxygenase (COX)-2 and the subsequent production of prostaglandin E2 (PGE2) were also induced by H-Ras. Treatment of H-Ras WB cells with GM6001 and NS398, the inhibitors of MMPs and COX-2, respectively, significantly inhibited the H-Ras-induced invasive and migrative phenotypes. DNA binding activity of nuclear factor (NF)-kappaB, but not that of activator protein (AP)-1, was increased by H-Ras. Caffeic acid phenethyl ester and Bay 11-7082, specific inhibitors of NF-kappaB and IKK, respectively, significantly inhibited the expression of MMP-9 and COX-2, invasion and migration of H-Ras WB cells, revealing NF-kappaB as a transcriptional factor responsible for H-Ras-induced malignant phenotypic conversion of WB cells. Activation of ERKs pathway was critical for H-Ras-induced invasive and migrative phenotypes, up-regulation of MMP-9 and COX-2 as well as enhanced DNA binding activity of NF-kappaB in WB cells. Taken together, these results demonstrate that H-Ras up-regulates MMP-9 and COX-2 through activation of ERKs and IKK-IkappaBalpha-NF-kappaB signal pathway which may contribute to the malignant progression of WB rat liver epithelial cells.

Antitumor Activity of an Oncolytic Adenovirus-Delivered Oncogene Small Interfering RNA

Despite successes in animal models, cancer gene therapy with small interfering RNAs (siRNA) is hindered by the lack of an optimal delivery platform. We examined the applicability of the replication-competent, oncolytic adenovirus, ONYX-411, to deliver a mutant K-ras siRNA transgene to human cancer cells. Proof-of-principle studies showed an additive tumor growth-inhibitory response through siRNA-mediated K-ras knockdown and ONYX-411-mediated cancer cell lysis. A novel construct, termed Internavec (for interfering RNA vector), was generated by cloning a K-ras(v12)-specific siRNA(ras-4) hairpin construct under the control of the human H1 promoter into the deleted E3b region of ONYX-411. Internavec acquired an increase in potency of approximately 10-fold in human cancer cells expressing the relevant K-ras(v12) mutation (H79, H441, and SW480), as defined by a reduction in the effective dose needed to achieve 50% growth inhibition (ED(50)). Internavec remained attenuated in nonmalignant epithelial cells. Daily intratumoral injections of Internavec (five daily injections of 1 x 10(8) plaque-forming units) significantly reduced the growth of s.c. H79 pancreatic cancer xenografts in nu/nu mice by 85.5%, including complete growth suppression in three of five mice. Parental ONYX-411 or ONYX-411-siRNA(GFP) was markedly less effective (47.8% growth reduction, P = 0.03; and 44.1% growth reduction, P = 0.03, respectively). siRNA(ras) transgene activity contributed to cell cycle blockage, increased apoptosis, and marked down-regulation of Ras signaling-related gene expression (AKT2, GSK3 beta, E2F2, and MAP4K5). These findings indicate that Internavec can generate a two-pronged attack on tumor cells through oncogene knockdown and viral oncolysis, resulting in a significantly enhanced antitumor outcome.

Modern challenges in colorectal cancer

Colorectal cancer is a major problem worldwide and in the United Kingdom it is responsible for some 20,000 deaths per annum. Mortality from the disease is gradually decreasing in developed countries but, in the United Kingdom at least, its incidence is on the increase. In this article the major current challenges in colorectal cancer will be dealt with under the following headings: aetiology and prevention, early detection, diagnosis, surgery, adjuvant therapy and management of advanced disease.

Ras stimulation of E2F activity and a consequent E2F regulation of integrin alpha6beta4 promote the invasion of breast carcinoma cells

Active Ras proteins contribute to breast carcinogenesis and progression. Here, we provide evidence that active H-Ras regulates the expression and activity of the E2F family of transcription factors in SUM-159 breast carcinoma cells. In addition, we show by using a DNA-binding mutant of E2F, as well as expression of specific E2Fs that are transcriptionally active, that the active E2Fs1-3 can mediate the H-Ras-dependent invasion of SUM-159 cells. The inhibitory E2Fs4-5, in contrast, do not influence invasion. One mechanism by which the active E2Fs promote H-Ras-dependent invasion seems to be their ability to increase expression of the beta4 integrin subunit, a component of the alpha6beta4 integrin that is known to enhance carcinoma invasion. Specifically, expression of E2Fs1-3 increased beta4 mRNA, protein, and cell surface expression. The active E2Fs were unable to stimulate invasion in cells that expressed a beta4 short hairpin RNA. This effect of the active E2Fs on beta4 expression does not seem to result from E2F-mediated beta4 transcription because the beta4 promoter lacks known E2F binding motifs. In summary, the data reported here indicate a novel mechanism by which H-Ras can promote the invasion of breast carcinoma cells. This mechanism links active H-Ras, transcriptionally active E2F, and the alpha6beta4 integrin in a common pathway that culminates in enhanced alpha6beta4-dependent invasion.