The role of Aquaporins in tumorigenesis: implications for therapeutic development

Aquaporins (AQPs) are ubiquitous channel proteins that play a critical role in the homeostasis of the cellular environment by allowing the transit of water, chemicals, and ions. They can be found in many different types of cells and organs, including the lungs, eyes, brain, glands, and blood vessels. By controlling the osmotic water flux in processes like cell growth, energy metabolism, migration, adhesion, and proliferation, AQPs are capable of exerting their regulatory influence over a wide range of cellular processes. Tumour cells of varying sources express AQPs significantly, especially in malignant tumours with a high propensity for metastasis. New insights into the roles of AQPs in cell migration and proliferation reinforce the notion that AQPs are crucial players in tumour biology. AQPs have recently been shown to be a powerful tool in the fight against pathogenic antibodies and metastatic cell migration, despite the fact that the molecular processes of aquaporins in pathology are not entirely established. In this review, we shall discuss the several ways in which AQPs are expressed in the body, the unique roles they play in tumorigenesis, and the novel therapeutic approaches that could be adopted to treat carcinoma.

Towards Understanding the Development of Breast Cancer: The Role of RhoJ in the Obesity Microenvironment

Obesity is a growing pandemic with an increasing risk of inducing different cancer types, including breast cancer. Adipose tissue is proposed to be a major player in the initiation and progression of breast cancer in obese people. However, the mechanistic link between adipogenicity and tumorigenicity in breast tissues is poorly understood. We used in vitro and in vivo approaches to investigate the mechanistic relationship between obesity and the onset and progression of breast cancer. In obesity, adipose tissue expansion and remodeling are associated with increased inflammatory mediator's release and anti-inflammatory mediators' reduction.. In order to mimic the obesity micro-environment, we cultured cells in an enriched pro-inflammatory cytokine medium to which we added a low concentration of beneficial adipokines. Epithelial cells exposed to the obesity micro-environment were phenotypically transformed into mesenchymal-like cells, characterized by an increase in different mesenchymal markers and the acquisition of the major hallmarks of cancerous cells; these include sustained DNA damage, the activation of the ATR-Chk2 pathway, an increase in proliferation rate, cell invasion, and resistance to conventional chemotherapy. Transcriptomic analysis revealed that several genes, including RhoJ, CCL7, and MMP9, acted as potential major players in the observed phenomenon. The transcriptomics findings were confirmed in vitro using qRT-PCR and in vivo using high-fat-diet-fed mice. Our data suggests RhoJ as a potential novel molecular driver of tumor development in breast tissues and a mediator of cell resistance to conventional chemotherapy through PAK1 activation. These data propose that RhoJ is a potential target for therapeutic interventions in obese breast cancer patients.

Comprehensive analysis of the role of ubiquitin-specific peptidases in colorectal cancer: A systematic review

BACKGROUND

Colorectal cancer (CRC) is the third most frequent and the second most fatal cancer. The search for more effective drugs to treat this disease is ongoing. A better understanding of the mechanisms of CRC development and progression may reveal new therapeutic strategies. Ubiquitin-specific peptidases (USPs), the largest group of the deubiquitinase protein family, have long been implicated in various cancers. There have been numerous studies on the role of USPs in CRC; however, a comprehensive view of this role is lacking.

AIM

To provide a systematic review of the studies investigating the roles and functions of USPs in CRC.

METHODS

We systematically queried the MEDLINE (via PubMed), Scopus, and Web of Science databases.

RESULTS

Our study highlights the pivotal role of various USPs in several processes implicated in CRC: Regulation of the cell cycle, apoptosis, cancer stemness, epithelial-mesenchymal transition, metastasis, DNA repair, and drug resistance. The findings of this study suggest that USPs have great potential as drug targets and noninvasive biomarkers in CRC. The dysregulation of USPs in CRC contributes to drug resistance through multiple mechanisms.

CONCLUSION

Targeting specific USPs involved in drug resistance pathways could provide a novel therapeutic strategy for overcoming resistance to current treatment regimens in CRC.

Potential anticancer properties of calotropis procera: An investigation on breast and colon cancer cells

Calotropis procera is a perennial flowering plant of the Apocynaceae family, traditionally used in medicine to treat various ailments. Recent investigations have revealed its potential therapeutic activities such as anti-inflammatory, gastroprotective, analgesic, anti-obesity, and anti-diabetic properties. RP-HPLC qualitatively and quantitatively evaluated the phenolic acids and flavonoids in the ethanolic extract at two different wavelengths, 280 and 330 nm. In addition, total phenolic and flavonoid contents were measured via spectrophotometric determination in addition to the antioxidant activity. The antiproliferative effects of C. procera were investigated on two cancer cell lines: human colon (HCT-116) and breast (MCF-7) cancer. Several methods were utilised to analyse the effectiveness of the plant extract on the cytotoxicity, apoptosis, cell cycle progression, genes involved in the cell cycle, and protein expression profiles of HCT-116 and MCF-7 cells. These included the MTT assay, Annexin V-FITC/PI, analysis of the cell cycle, and Western blot. Results indicated that ferulic and caffeic acids were the major compounds at λ_max 280 nm (1.374% and 0.561%, respectively), while the major compounds at λ_max 325 nm were kaempferol and luteolin (1.036% and 0.512%, respectively). The ethanolic extract had significantly higher antioxidant activity (80 ± 2.3%) compared to ascorbic acid (90 ± 3.1%). C. procera extract exhibited dose-dependent cell growth inhibition, with an estimated IC₅₀ of 50 μg/mL for MCF-7 and 55 μg/mL for HCT-116 cells at 24 h. Annexin V-FITC/PI confirmed the induction of apoptosis. Remarkably, cell cycle arrest occurred at the sub-G1 phase in MCF-7 cells, while in HCT-116 cells, it was observed at the G2-M phase. The sub-G1 arrest was associated with dysregulation of Akt, p-AKT, mTOR, and p-mTOR proteins, as confirmed by the Western blot analysis, while downregulation of CDK1, cyclin B1, and survivin caused G2-M arrest.

Immunohistochemical Expression Analysis of Caldesmon Isoforms in Colorectal Carcinoma Reveals Interesting Correlations with Tumor Characteristics

Colorectal cancer is a notorious disease, with almost half of the patients succumbing to the disease. The prevalence and incidence rates of colorectal cancer are increasing in many parts of the world, highlighting the need to discover new biomarkers for diagnosis and therapy. Caldesmon (CaD), an actin-binding protein that plays a significant role in controlling cell motility, has emerged as a promising biomarker. The CALD1 gene encodes CaD as multiple transcripts that mainly encode two protein isoforms: High-molecular-weight (h-CaD), expressed in smooth muscle, and low-molecular-weight (l-CaD), expressed in nonsmooth muscle cells. Most studies have suggested an oncogenic role of CaD in colorectal cancer, but the exact subcellular localization of the two CaD isoforms in tumor cells and stroma have not been clarified yet. Here, we analyzed tissue samples from 262 colorectal cancer patients by immunohistochemistry analysis using specific antibodies for l-CaD and h-CaD. The results showed elevated cytoplasmic expression levels of l-Cad in 187/262 (71.4%) cases. l-Cad was expressed at low levels in the normal colon mucosa and was also consistently expressed in the cancer-associated stroma of all cases, suggesting that it could play a role in modulating the tumor microenvironment. l-CaD expression in cancer cells was associated with preinvasive stages of cancer. Survival analysis indicated that patients with high l-CaD expression in tumor cells could respond poorly to selective chemotherapeutic 5FU, but not combination chemotherapy. h-CaD was expressed in colonic and vascular smooth muscle cells as expected and to a lesser extent in the tumor-associated stroma, but it was not expressed in the cancer cells or normal colon mucosal epithelial cells. Collectively, these data clarify how the expression patterns of CaD isoforms in colorectal cancer can have applications in the management of colorectal cancer patients.

Characterization of the Molecular Alterations Induced by the Prolonged Exposure of Normal Colon Mucosa and Colon Cancer Cells to Low-Dose Bisphenol A

Colorectal cancer is a common cancer with a poor prognosis in both males and females. The influence of bisphenol A (BPA), a widely used environmental contaminant, in colon cancer development and progression is not well identified, in spite of the fact that the most common mode of exposure to BPA is ingestion. The aim of this work is to elucidate the carcinogenic effects of BPA in the colon in vitro. We analyzed BPA’s effects on human colon epithelial (HCoEpiC) and colon cancer (HCT116) cells. BPA exerted cytotoxic effects and augmented the 5FU cytotoxicity on both cell lines at high doses, while it did not show this effect at low doses. Therefore, we focused on studying the effects of low-dose (0.0043 nM) exposure on normal colonic epithelial cells for a long period of time (two months), which is more consistent with environmental exposure levels and patterns. BPA increased cellular invasiveness through collagen and the ability to anchorage-independent cell growth, as measured by colony formation in soft agar, which could support oncogenicity. To gain insights into the mechanism of these actions, we performed transcriptomic analysis using next-generation sequencing, which revealed 340 differentially expressed transcripts by BPA in HCT116 and 75 in HCoEpiC. These transcripts belong in many cancer-related pathways such as apoptosis, cell proliferation, signal transduction, and angiogenesis. Some of the significant genes (FAM83H, CXCL12, PITPNA, HMOX1, DGKZ, NR5A2, VMP1, and ID1) were confirmed by quantitative RT-PCR. Furthermore, BPA induced the phosphorylation of protein kinases such as JNK1/2/3, GSK-3α/β, AMPKα1, AKT1/2/3, AMPKα2, HSP27, β-catenin, STAT2, Hck, Chk2, FAK, and PRAS40 in HCoEpiC, as well as GSK-3α/β, p53, AKT1/2/3, p70 S6 kinase, and WNK1 in HCT116. The majority of these proteins are involved in potential carcinogenic pathways. Taken together, these data suggest that BPA plays a role in colon carcinogenesis, and they provide insights into the molecular mechanisms of colon epithelial cell transformation by BPA. Increasing exposure to environmental toxins such as BPA can explain the increasing incidence of colorectal cancer.

Emerging role of caldesmon in cancer: A potential biomarker for colorectal cancer and other cancers

Colorectal cancer (CRC) is a devastating disease, mainly because of metastasis. As a result, there is a need to better understand the molecular basis of invasion and metastasis and to identify new biomarkers and therapeutic targets to aid in managing these tumors. The actin cytoskeleton and actin-binding proteins are known to play an important role in the process of cancer metastasis because they control and execute essential steps in cell motility and contractility as well as cell division. Caldesmon (CaD) is an actin-binding protein encoded by the CALD1 gene as multiple transcripts that mainly encode two protein isoforms: High-molecular-weight CaD, expressed in smooth muscle, and low-molecular weight CaD (l-CaD), expressed in nonsmooth muscle cells. According to our comprehensive review of the literature, CaD, particularly l-CaD, plays a key role in the development, metastasis, and resistance to chemoradiotherapy in colorectal, breast, and urinary bladder cancers and gliomas, among other malignancies. CaD is involved in many aspects of the carcinogenic hallmarks, including epithelial mesenchymal transition via transforming growth factor-beta signaling, angiogenesis, resistance to hormonal therapy, and immune evasion. Recent data show that CaD is expressed in tumor cells as well as in stromal cells, such as cancer-associated fibroblasts, where it modulates the tumor microenvironment to favor the tumor. Interestingly, CaD undergoes selective tumor-specific splicing, and the resulting isoforms are generally not expressed in normal tissues, making these transcripts ideal targets for drug design. In this review, we will analyze these features of CaD with a focus on CRC and show how the currently available data qualify CaD as a potential candidate for targeted therapy in addition to its role in the diagnosis and prognosis of cancer.

Evaluation of Galanin Expression in Colorectal Cancer: An Immunohistochemical and Transcriptomic Study

Colorectal cancer (CRC) represents around 10% of all cancers, with an increasing incidence in the younger age group. The gut is considered a unique organ with its distinctive neuronal supply. The neuropeptide, human galanin, is widely distributed in the colon and expressed in many cancers, including the CRC. The current study aimed to explore the role of galanin at different stages of CRC. Eighty-one CRC cases (TNM stages I – IV) were recruited, and formalin-fixed paraffin-embedded samples were analyzed for the expression of galanin and galanin receptor 1 (GALR1) by immunohistochemistry (IHC). Galanin intensity was significantly lower in stage IV (n= 6) in comparison to other stages (p= 0.037 using the Mann-Whitney U test). Whole transcriptomics analysis using NGS was performed for selected samples based on the galanin expression by IHC [early (n=5) with high galanin expression and late (n=6) with low galanin expression]. Five differentially regulated pathways (using Absolute GSEA) were identified as drivers for tumor progression and associated with higher galanin expression, namely, cell cycle, cell division, autophagy, transcriptional regulation of TP53, and immune system process. The top shared genes among the upregulated pathways are AURKA, BIRC5, CCNA1, CCNA2, CDC25C, CDK2, CDK6, EREG, LIG3, PIN1, TGFB1, TPX2. The results were validated using real-time PCR carried out on four cell lines [two primaries (HCT116 and HT29) and two metastatic (LoVo and SK-Co-1)]. The current study shows galanin as a potential negative biomarker. Galanin downregulation is correlated with advanced CRC staging and linked to cell cycle and division, autophagy, transcriptional regulation of TP53 and immune system response.

Ramadan Diurnal Intermittent Fasting Is Associated With Attenuated FTO Gene Expression in Subjects With Overweight and Obesity: A Prospective Cohort Study

Aim and Background

A growing body of evidence supports the impact of intermittent fasting (IF) on normalizing body weight and that the interaction between body genes and environmental factors shapes human susceptibility to developing obesity. FTO gene is one of these genes with metabolic effects related to energy metabolism and body fat deposition. This research examined the changes in FTO gene expression upon Ramadan intermittent fasting (RIF) in a group of metabolically healthy subjects with overweight and obesity.

Methods

Sixty-three (63) subjects were recruited, of which 57 (17 males and 40 females, mean age 38.4 ± 11.2 years) subjects with overweight and obesity (BMI = 29.89 ± 5.02 kg/m2were recruited and monitored before and at the end of Ramadan month), and 6 healthy subjects with normal BMI (21.4 ± 2.20 kg/m2) recruited only to standardize the reference for normal levels of FTO gene expression. In the two-time points, anthropometric, biochemical, and dietary assessments were undertaken, and FTO gene expression tests were performed using RNA extracted from the whole blood sample.

Results

In contrast to normal BMI subjects, the relative gene expressions in overweight/obese were significantly decreased at the end of Ramadan (−32.30%, 95% CI–0.052 −0.981) in comparison with the pre-fasting state. Significant reductions were found in body weight, BMI, fat mass, body fat percent, hip circumference, LDL, IL-6, TNF-α (P<0.001), and in waist circumference (P<0.05), whilst HDL and IL-10 significantly increased (P<0.001) at the end of Ramadan in comparison with the pre-fasting levels. Binary logistic regression analysis for genetic expressions showed no significant association between high-energy intake, waist circumference, or obesity and FTO gene expression.

Conclusions

RIF is associated with the downregulation of the FTO gene expression in subjects with obesity, and this may explain, at least in part, its favorable metabolic effects. Hence, RIF presumably may entail a protective impact against body weight gain and its adverse metabolic-related derangements in subjects with obesity.

Obesity and inflammation: colorectal cancer engines

The prevalence of obesity continues to increase to the extent that it became a worldwide pandemic. An accumulating body of evidence has associated obesity with the development of different types of cancer, including colorectal cancer, which is a notorious disease with a high mortality rate. At the molecular level, colorectal cancer is a heterogenous disease characterized by a myriad of genetic and epigenetic alterations associated with various forms of genomic instability (detailed in Supplementary Materials). Recently, the microenvironment has emerged as a major factor in carcinogenesis. Our aim is to define the different molecular alterations leading to the development of colorectal cancer in obese patients with a focus on the role of the microenvironment in carcinogenesis. We also highlight all existent molecules in clinical trials that target the activated pathways in obesity-associated colorectal cancer, whether used as single treatments or in combination. Obesity predisposes to colorectal cancer via creating a state of chronic inflammation with dysregulated adipokines, inflammatory mediators, and other factors such as immune cell infiltration. A unifying theme in obesity-mediated colorectal cancer is the activation of the PI3K/AKT, mTOR/MAPK, and STAT3 signaling pathways. Different inhibitory molecules towards these pathways exist, increasing the therapeutic choice of obesity-associated colon cancer. However, obese patients are more likely to suffer from chemotherapy overdosing. Preventing obesity through maintaining a healthy and active lifestyle remains to be the best remedy.

Chronic Inflammation and Cancer: The Role of Endothelial Dysfunction and Vascular Inflammation

Long-lasting subclinical inflammation is associated with a wide range of human diseases, particularly at a middle and older age. Recent reports showed that there is a direct causal link between inflammation and cancer development, as several cancers were found to be associated with chronic inflammatory conditions. In patients with cancer, healthy endothelial cells regulate vascular homeostasis, and it is believed that they can limit tumor growth, invasiveness, and metastasis. Conversely, dysfunctional endothelial cells that have been exposed to the inflammatory tumor microenvironment can support cancer progression and metastasis. Dysfunctional endothelial cells can exert these effects via diverse mechanisms, including dysregulated adhesion, permeability, and activation of NF-κB and STAT3 signaling. In this review, we highlight the role of vascular inflammation in predisposition to cancer within the context of two common disease risk factors: obesity and smoking. In addition, we discuss the molecular triggers, pathophysiological mechanisms, and the biological consequences of vascular inflammation during cancer development and metastasis. Finally, we summarize the current therapies and pharmacological agents that target vascular inflammation and endothelial dysfunction.

Antioxidant Properties of Olive Mill Wastewater Polyphenolic Extracts on Human Endothelial and Vascular Smooth Muscle Cells

This work aims to analyze the chemical and biological evaluation of two extracts obtained by olive mill wastewater (OMW), an olive oil processing byproduct. The exploitation of OMW is becoming an important aspect of development of the sustainable olive oil industry. Here we chemically and biologically evaluated one liquid (L) and one solid (S) extract obtained by liquid–liquid extraction followed by acidic hydrolysis (LLAC). Chemical characterization of the two extracts indicated that S has higher phenol content than L. Hydroxytyrosol and tyrosol were the more abundant phenols in both OMW extracts, with hydroxytyrosol significantly higher in S as compared to L. Both extracts failed to induce cell death when challenged with endothelial cells and vascular smooth muscle cells in cell viability experiments. On the contrary, the higher extract dosages employed significantly affected cell metabolic activity, as indicated by the MTT tests. Their ability to counteract H₂O₂-induced oxidative stress and cell death was assessed to investigate potential antioxidant activities of the extracts. Fluorescence measurements obtained with the reactive oxygen species (ROS) probe H₂DCF-DA indicated strong antioxidant activity of the two OMW extracts in both cell models, as indicated by the inhibition of H₂O₂-induced ROS generation and the counteraction of the oxidative-induced cell death. Our results indicate LLAC-obtained OMW extracts as a safe and useful source of valuable compounds harboring antioxidant activity.

The Endocrine Disruptor Bisphenol A (BPA) Exerts a Wide Range of Effects in Carcinogenesis and Response to Therapy

BACKGROUND

Bisphenol A (BPA) is a synthetic plasticizer that is commonly used in the production of polycarbonate plastics and epoxy resins. Human exposure occurs when BPA migrates from food and beverage containers into the contents when heated or even under normal conditions of use. BPA exerts endocrine disruptor action due to its weak binding affinity for the estrogen receptors ERα and ERβ. BPA exerts other effects by activating the membrane receptor GPER (GPR30) and/or other receptors such as the estrogen-related receptors (ERRs).

OBJECTIVE

This review summarizes emerging data on BPA and cancer. These include data linking exposure to BPA with an increased risk of hormone-related cancers such as those of the ovary, breast, prostate, and even colon cancer. BPA can also induce resistance to various chemotherapeutics such as doxorubicin, cisplatin, and vinblastine in vitro. The development of chemoresistance to available therapeutics is an emerging significant aspect of BPA toxicity because it worsens the prognosis of many tumors.

CONCLUSION

Recent findings support a causal role of BPA at low levels in the development of cancers and in dictating their response to cytotoxic therapy. Accurate knowledge and consideration of these issues would be highly beneficial to cancer prevention and management.

Potential Adverse Effects of Resveratrol: A Literature Review

Due to its health benefits, resveratrol (RE) is one of the most researched natural polyphenols. Resveratrol's health benefits were first highlighted in the early 1990s in the French paradox study, which opened extensive research activity into this compound. Ever since, several pharmacological activities including antioxidant, anti-aging, anti-inflammatory, anti-cancerous, anti-diabetic, cardioprotective, and neuroprotective properties, were attributed to RE. However, results from the available human clinical trials were controversial concerning the protective effects of RE against diseases and their sequelae. The reason for these conflicting findings is varied but differences in the characteristics of the enrolled patients, RE doses used, and duration of RE supplementation were proposed, at least in part, as possible causes. In particular, the optimal RE dosage capable of maximizing its health benefits without raising toxicity issues remains an area of extensive research. In this context, while there is a consistent body of literature on the protective effects of RE against diseases, there are relatively few reports investigating its possible toxicity. Indeed, toxicity and adverse effects were reported following consumption of RE; therefore, extensive future studies on the long-term effects, as well as the in vivo adverse effects, of RE supplementation in humans are needed. Furthermore, data on the interactions of RE when combined with other therapies are still lacking, as well as results related to its absorption and bioavailability in the human body. In this review, we collect and summarize the available literature about RE toxicity and side effects. In this process, we analyze in vitro and in vivo studies that have addressed this stilbenoid. These studies suggest that RE still has an unexplored side. Finally, we discuss the new delivery methods that are being employed to overcome the low bioavailability of RE.

Calponin 3 promotes invasion and drug resistance of colon cancer cells

BACKGROUND

Calponin 3 (CNN3) is an actin-binding protein expressed in smooth muscle and non-smooth muscle cells. It is required for cytoskeletal rearrangement and wound healing.

AIM

To dissect the role of CNN3 in carcinogenesis with a focus on colon cancer.

METHODS

A total of 20 cancer cell lines (8 breast, 11 colon, and HeLa cervical cancer cell as a positive control for mesenchymal phenotype) and 57 formalin-fixed, paraffin-embedded sections from archived sporadic colorectal carcinomas were included in this study. CNN3 expression analysis by western blot or immunohistochemistry was followed by functional analyses. The CNN3 gene was silenced by specific small interfering RNA (commonly known as siRNA), followed by confirmation of the silencing efficiency by western blotting. Then, the silenced cells and control siRNA-transfected cells were analyzed for changes in epithelial and mesenchymal markers, invasion, and response to 5-fluoruracil treatment. We also performed proteomics analysis using a phospho-kinase array-based panel of 45 proteins.

RESULTS

CNN3 showed positive expression in 6/8 breast and 9/11 colon cancer lines and in HeLa cells. Interestingly, the colorectal adenocarcinoma line SW480 was negative, while the cell line developed from its matching lymph node metastasis (SW620) was positive for CNN3. CNN3 expression was fairly consistent with the metastatic phenotype in colon cancer because it was absent in one other colon cell line from a primary site and expressed in all others. We selected SW620 for subsequent functional analyses. CNN3-silenced SW620 cells showed a reduction in collagen invasion and loss of mesenchymal markers. CNN3 silencing caused an increase in the SW620 colon cancer cell sensitivity to 5-fluorouracil. Phospho-kinase array-based proteomics analysis showed that CNN3 silencing in SW620 reduced extracellular signal-regulated kinase, β-Catenin, mutant p53, c-Jun, and heat shock protein 60 activities but increased that of checkpoint kinase 2. CNN3 was expressed in 20/57 (35%) colon cancer cases as shown by immunohistochemistry. CNN3 was associated with a decrease in overall survival in colon cancer in silico.

CONCLUSION

These results show the involvement of CNN3 in lymph node metastasis and resistance to chemotherapy in colon cancer and suggest that significant oncogenic pathways are involved in these CNN3-related actions.

Molecular Determinants of Colon Cancer Susceptibility in the East and West

The currently available knowledge of factors that dictate the development and progression as well as the clinical outcome of colorectal cancers (CRC) is mainly derived from Western countries. Considerable number of publications document different incidence rates and contrasting clinical features of CRC in various groups such as the differences between urban vs. rural areas, young vs. old age and the East vs. the West. In particular, Egyptian CRC is a surprisingly young age disease with higher proportion of poorly differentiated and advanced stage cancers as compared to the Western counterparts. Less number of publications addressed the molecular genetics and epigenetic basis of these differences. The available data on CRC and other cancers support a substantial role of several environmental risk factors which impinge on the epigenome and alter the overall cellular and tissue homeostasis. Thus, environmental factors could play a role in predisposition to CRC in general as well as in shaping distinct disease phenotypes in different settings. On the other hand, the environment offers a wide range of preventive modalities including a selection of dietary chemopreventive agents which could play a significant role in fighting cancer at early stages. We here compare the clinical and molecular characteristics of Eastern and Western CRC based on the latest literature. The genetic, epigenetic and environmental etiologies for the observed differences are discussed. Finally, prospects for cancer prevention in light of the increased etiologic understanding are outlined.

The role of p53-microRNA 200-Moesin axis in invasion and drug resistance of breast cancer cells

This study aimed to analyze the expression of microRNAs in relation to p53 status in breast cancer cells and to delineate the role of Moesin in this axis. We used three isogenic breast carcinoma cell lines MCF7 (with wild-type p53), 1001 (MCF7 with mutated p53), and MCF7-E6 (MCF7 in which p53 function was disrupted). MicroRNA expression was analyzed using microarray analysis and confirmed by real-time polymerase chain reaction. The 1001 clone with mutant p53 showed 22 upregulated and 25 downregulated microRNAs. The predicted targets of these 47 microRNAs were >700 human genes belonging to interesting functional groups such as stem cell development and maintenance. The most significantly downregulated microRNAs in the p53-mutant cell line were from the miR-200 family. We focused on miR-200c which targets many transcripts involved in epithelial-to-mesenchymal transition including Moesin. We found that Moesin was expressed in 1001 but not in its p53 wild-type parental MCF7 consistent with the observed mesenchymal features in the 1001, such as vimentin positivity, E-cadherin negativity, and ZEB1 positivity in addition to the morphological changes. After Moesin silencing, the p53-mutant cells 1001 reverted from mesenchymal-to-epithelial phenotype and showed subtle reduction in migration and invasion and loss of ZEB1 and SNAIL expression. Interestingly, Moesin silencing restored the 1001 sensitivity to Doxorubicin. These results indicate that loss of miR-200c, as a consequence of p53 mutation, can upregulate Moesin oncogene and thus promote carcinogenesis. Moesin may play a role in metastasis and drug resistance of breast cancer.

Role of AXL in invasion and drug resistance of colon and breast cancer cells and its association with p53 alterations

AIM

To characterize AXL receptor tyrosine kinase (AXL) expression in relationship to tumor protein P53 (TP53 gene, p53 protein) and its role in tumor invasion and response to therapy.

METHODS

We used 14 cell lines, including 3 isogenic pairs carrying mutant/knockout p53, to gain insight into the relationship between AXL and TP53. These included HCT116, HCT116.p53 mutant, RKO, and RKO.p53^-/- lines (all from colon cancers) as well as breast cancer cell lines MCF7 and 1001 (MCF7-p53 mutant clone). HeLa cell line was used as a positive control for epithelial to mesenchymal transition (EMT). AXL expression was determined by Western blotting using rabbit monoclonal antibody clone C89E7. AXL siRNA silencing was performed and followed by collagen invasion assay. Cell viability analysis using the sulforhodamine B assay and the invasion assay were performed after exposure to chemotherapeutic agents (doxorubicin for breast cancer cells; 5FU or irinotecan for colon cancer cells).

RESULTS

We showed that the introduction of p53 mutations or knockout increased expression levels of AXL in isogenic cells compared to the matching p53 wild-type parental cells. Overall, we found a trend for correlation between the potential EMT candidate AXL, p53 alterations, and EMT markers in colorectal and breast cancers. The expression of AXL in RKO cells, a rare colon cancer cell line with inactive Wnt signaling, suggests that the AXL oncogene might provide an alternative genetic pathway for colorectal carcinogenesis in the absence of Wnt signaling activation and TP53 mutation. AXL silencing in the TP53 mutant isogenic cell lines 1001, HCT116.p53 mutant and RKO.P53^-/- was > 95% efficient and the silenced cells were less invasive compared to the parental TP53 wild-type cells. AXL silencing showed a subtle trend to restore colon cancer cell sensitivity to 5FU or irinotecan. Importantly, AXL expressing cells developed more invasive potential after exposure to chemotherapy compared to the AXL-silenced cells.

CONCLUSION

AXL is influenced by p53 status and could cause the emergence of aggressive clones after exposure to chemotherapy. These findings could have applications in cancer management.

Methyltransferase expression and tumor suppressor gene methylation in sporadic and familial colorectal cancer

Molecular mechanisms underlying coordinated hypermethylation of multiple CpG islands in cancer remain unclear and studies of methyltransferase enzymes have arrived at conflicting results. We focused on DNMT1 and DNMT3B, DNA methyltransferases responsible for (de novo) methylation, and EZH2, histone (H3K27) methyltransferase, and examined their roles in tumor suppressor gene (TSG) methylation patterns we have previously established in sporadic and familial cancers. Our investigation comprised 165 tumors, stratified by tissue of origin (117 colorectal and 48 endometrial carcinomas) and sporadic vs. familial disease (57 sporadic vs. 60 familial, mainly Lynch syndrome, colorectal carcinomas). By immunohistochemical evaluation, EZH2 protein expression was associated with a TSG methylator phenotype. DNMT1, DNMT3B, and EZH2 were expressed at significantly higher levels in tumor vs. normal tissues. DNMT1 and EZH2 expression were positively correlated and higher in microsatellite-unstable vs. microsatellite-stable tumors, whether sporadic or hereditary. Ki-67 expression mirrored the same pattern. Promoter methylation of the methyltransferase genes themselves was addressed as a possible cause behind their altered expression. While DNMT1 or EZH2 did not show differential methylation between normal and tumor tissues, DNMT3B analysis corroborated the regulatory role of a distal promoter region. Our study shows that methyltransferase expression in cancer depends on the tissue of origin, microsatellite-instability status, cellular proliferation, and--in the case of DNMT3B--promoter methylation of the respective gene. Translation of methyltransferase expression into DNA methylation appears complex as suggested by the fact that except for EZH2, no clear association between methyltransferase protein expression and TSG methylation was observed.

Germline mutation of RPS20, encoding a ribosomal protein, causes predisposition to hereditary nonpolyposis colorectal carcinoma without DNA mismatch repair deficiency

Little is known about the genetic factors that contribute to familial colorectal cancer type X (FCCX), characterized by hereditary nonpolyposis colorectal carcinoma with no mismatch repair defects. Genetic linkage analysis, exome sequencing, tumor studies, and functional investigations of 4 generations of a FCCX family led to the identification of a truncating germline mutation in RPS20, which encodes a component (S20) of the small ribosomal subunit and is a new colon cancer predisposition gene. The mutation was associated with a defect in pre-ribosomal RNA maturation. Our findings show that mutations in a gene encoding a ribosomal protein can predispose individuals to microsatellite-stable colon cancer. Evaluation of additional FCCX families for mutations in RPS20 and other ribosome-associated genes is warranted.

Antagonism between curcumin and the topoisomerase II inhibitor etoposide: a study of DNA damage, cell cycle regulation and death pathways

The use of combinations of chemotherapy and natural products has recently emerged as a new method of cancer therapy, relying on the capacity of certain natural compounds to trigger cell death with low doses of chemotherapeutic agents and few side effects. The current study aims to evaluate the modulatory effects of curcumin (CUR), Nigella sativa (NS) and taurine on etoposide (ETP) cytotoxicity in a panel of cancer cell lines and to identify their underlying mechanisms. CUR alone showed potent antitumor activity, but surprisingly, its interaction with ETP was antagonistic in four out of five cancer cell lines. Neither taurine nor Nigella sativa affect the sensitivity of cancer cells to ETP. Examination of the DNA damage response machinery (DDR) showed that both ETP and CUR elicited DNA double-strand breaks (DSB) and evoked γ-H2AX foci formation at doses as low as 1 µg/ml. Cell cycle analysis revealed S phase arrest after ETP or CUR application, whereas co-treatment with ETP and CUR led to increased arrest of the cell cycle in S phase (MCF-7 cells) or the accumulation of cells in G 2/M phases (HCT116, and HeLa cells). Furthermore, cotreatment with ETP and CUR resulted in modulation of the level of DNA damage induction and repair compared with either agent alone. Electron microscopic examination demonstrated that different modalities of cell death occurred with each treatment. CUR alone induced autophagy, apoptosis and necrosis, whereas ETP alone or in combination with CUR led to apoptosis and necrosis.

CONCLUSIONS

Cotreatment with ETP and CUR resulted in an antagonistic interaction. This antagonism is related, in part, to the enhanced arrest of tumor cells in both S and G 2/M phases, which prevents the cells from entering M-phase with damaged DNA and, consequently, prevents cell death from occurring. This arrest allows time for the cells to repair DNA damage so that cell cycle -arrested cells can eventually resume cell cycle progression and continue their physiological program.

Differential roles of EPS8 in carcinogenesis: Loss of protein expression in a subset of colorectal carcinoma and adenoma

AIM: To analyze the epidermal growth factor receptor pathway substrate 8 (EPS8) expression status and role in colorectal carcinogenesis given that EPS8 has a conserved actin barbed-end capping function that is required for proper maturation in intestinal cells.

METHODS: We studied 8 colon cancer cell lines and 58 colorectal tumors (19 adenomas and 39 carcinomas). We performed expression microarray analysis of colon cancer cell lines followed by loss of heterozygosity (LOH) analysis and immunohistochemistry for EPS8 expression in colon tumors. Subsequently, we performed mutation analysis by direct sequencing and methylation analysis by bisulfite sequencing and methylation-specific polymerase chain reaction assays.

RESULTS: Expression microarray analysis of colon cancer cell lines showed overexpression of EPS8 transcript in all lines but RKO. Genome wide loss of heterozygosity (LOH) analysis of colon tumors, showed considerable LOH at the EPS8 gene locus. Immunohistochemically, EPS8 was constitutively expressed in normal colonic mucosa with a dot-like supranuclear localization with accentuation at the luminal surface supporting its proposed role in epithelial maturation. Nineteen colon tumors (4 adenoma, 15 carcinoma) out of 51 (37%) showed strikingly tumor specific EPS8 protein loss. Of the remaining tumors, 5/51 (2 adenoma, and 3 carcinoma, 10%) showed marked overexpression, while 27/51 tumors (53%) showed retained expression. Mutation analysis revealed a missense mutation (c.794C>T, p.R265C) in exon 8 in RKO. The EPS8 promoter was also methylated in RKO, but there was no significant methylation in other cell lines or carcinoma specimens.

CONCLUSION: The loss of EPS8 expression in colorectal adenomas and carcinomas suggests that down regulation of this gene contributes to the development of a subset of colorectal cancers, a finding which could have applications in diagnosis and treatment.

Breast carcinoma and Lynch syndrome: molecular analysis of tumors arising in mutation carriers, non-carriers, and sporadic cases

Introduction

Breast carcinoma is the most common cancer in women, but its incidence is not increased in Lynch syndrome (LS) and studies on DNA mismatch repair deficiency (MMR) in LS-associated breast cancers have arrived at conflicting results. This study aimed to settle the question as to whether breast carcinoma belongs to the LS tumor spectrum.

Methods

MMR status and epigenetic profiles were determined for all available breast carcinomas identified among 200 LS families from a nation-wide registry (23 tumors from mutation carriers and 18 from non-carriers). Sporadic breast carcinomas (n = 49) and other cancers (n = 105) from MMR gene mutation carriers were studied for comparison.

Results

The proportion of breast carcinomas that were MMR-deficient based on absent MMR protein, presence of microsatellite instability, or both was significantly (P = 0.00016) higher among breast carcinomas from mutation carriers (13/20, 65%) compared to non-carriers (0/14, 0%). While the average age at breast carcinoma diagnosis was similar in carriers (56 years) and non-carriers (54 years), it was lower for MMR-deficient versus proficient tumors in mutation carriers (53 years versus 61 years, P = 0.027). Among mutation carriers, absent MMR protein was less frequent in breast carcinoma (65%) than in any of seven other tumor types studied (75% to 100%). Tumor suppressor promoter methylation patterns were organ-specific and similar between breast carcinomas from mutation carriers and non-carriers.

Conclusions

Breast carcinoma from MMR gene mutation carriers resembles common breast carcinoma in many respects (for example, general clinicopathological and epigenetic profiles). MMR status makes a distinction: over half are MMR-deficient typical of LS spectrum tumors, while the remaining subset which is MMR-proficient may develop differently. The results are important for appropriate surveillance in mutation carriers and may be relevant for LS diagnosis in selected cases.

Abstract 5018: Genetic and epigenetic investigation of breast carcinoma arising in Lynch syndrome families

Breast carcinoma is the most common cancer type in females, but its incidence is generally not increased in Lynch syndrome (LS). Deficient DNA mismatch repair (MMR) is a hallmark of LS tumors that are unequivocal manifestations of the syndrome (e.g., colorectal and breast carcinoma). Because of controversial study results, it is unclear at present whether or not breast carcinoma is specifically associated with LS. We addressed this question by determining the genetic and epigenetic profiles for all available breast carcinomas from LS families from a nation-wide registry, including 24 tumors from MMR gene mutation carriers and 17 tumors from non-carriers. The average age at breast carcinoma diagnosis was similar in mutation carriers and non-carriers (56 years for each). Among breast carcinomas from mutation carriers, 43% showed loss of MMR protein corresponding to the germline mutation, and high-degree microsatellite instability (MSI-H) was present in 36%. Moreover, in mutation carriers, the age at diagnosis was lower for breast carcinomas that were MMR-deficient (by absent MMR protein and/or MSI present) compared to MMR proficient tumors (51 vs. 60 years, p= 0.031). Breast carcinomas showed frequent inactivation of tumor suppressor genes (TSG) by promoter methylation. The average number of methylated TSGs out of 24 per tumor was 3.1 for mutation carriers and 2.8 for non-carriers. The gene-specific distribution of methylation was also similar between the two breast tumor sets. In mutation carriers, the most frequently methylated TSGs were RASSF1 (77%), APC (45%), CDH13 (45%), GSTP1 (32%) and CDKN2B (27%). In non-carriers, the respective frequencies were 75%, 47%, 59%, 35%, and 29%. When compared to tumors arising in other organs from LS mutation carriers, methylation of CDKN2B was seen as a particular characteristic of breast tumorigenesis. Our investigation shows that TSG promoter methylation is a common characteristic of breast carcinomas arising in LS and affects mutation carriers and non-carriers with comparable overall rates and gene-specific distributions. Analysis of MMR protein expression and MSI revealed that while many breast carcinomas from LS mutation carriers follow MMR-driven tumorigenesis characteristic of tumors of the LS spectrum in general, a significant subset of breast tumors also exists that appears to arise and progress along separate pathways.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5018. doi:1538-7445.AM2012-5018

Distinct genetic and epigenetic signatures of colorectal cancers according to ethnic origin

BACKGROUND

The outcome of colorectal cancer varies depending on ethnic origin. Egyptian colorectal carcinoma is surprisingly young-age disease with high proportion of rectal and advanced stage cancers.

METHODS

We characterized 69 sporadic Egyptian colorectal cancers for promoter methylation at 24 tumor suppressor genes, microsatellite instability, and expression of mismatch repair, p53, and β-catenin proteins. Data were compared with 80 Western colorectal carcinoma of sporadic and familial origin from Finland.

RESULTS

Egyptian colorectal carcinomas showed significantly higher methylation of the microsatellite stable (MSS) tumors as reflected by the average number of methylated genes per case (P = 0.00002) and tumor suppressor gene methylator phenotype (TSGMP), defined here as methylation of ≥ 5 genes, (P = 0.0001) compared with the sporadic Western cancers. The TSGMP was associated with advanced stage in the Egyptian cancers (P = 0.0016). Four genes were differentially methylated between Egyptian and Western cases, of which the association of CDKN2B/p15 methylation with Egyptian origin was outstanding (P = 4.83 E-10). Egyptian carcinoma also showed significantly lower frequency of nuclear β-catenin localization than the sporadic Western cancers (P = 0.00006) but similar to that of the familial Western subset designated as familial colorectal cancer type X.

CONCLUSIONS

We show novel pathway in colon carcinogenesis marked by high methylation of MSS cancers, remarkable CDKN2B/p15 methylation, and low frequency of Wnt signaling activation.

IMPACT

Our findings highlight the possible effect of environmental exposures in carcinogenesis through DNA methylation and should have applications in prevention, molecular diagnosis, prognosis, and treatment.

Genomic instability and carcinogenesis: an update

Cancers arise as a result of stepwise accumulation of mutations which may occur at the nucleotide level and/or the gross chromosomal level. Many cancers particularly those of the colon display a form of genomic instability which may facilitate and speed up tumor initiation and development. In few instances, a "mutator mutation" has been clearly implicated in driving the accumulation of other carcinogenic mutations. For example, the post-replicative DNA mismatch repair deficiency results in dramatic increase in insertion/deletion mutations giving rise to the microsatellite instability (MSI) phenotype and may predispose to a spectrum of tumours when it occurs in the germline. Although many sporadic cancers show multiple mutations suggesting unstable genome, the role of this instability in carcinogenesis, as opposed to the power of natural selection, has been a matter of controversy. This review gives an update of the latest data on these issues particularly recent data from genome-wide, high throughput techniques as well as mathematical modelling. Throughout this review, reference will be made to the relevance of genomic instability to the pathogenesis of colorectal carcinoma particularly its hereditary and familial subsets.

Molecular analysis of endometrial tumorigenesis: importance of complex hyperplasia regardless of atypia

PURPOSE

Endometrial carcinoma (EC) is common in the population and the most frequent extracolonic malignancy in hereditary nonpolyposis colorectal carcinoma (HNPCC)/Lynch syndrome. We characterized precursor lesions of endometrioid EC to identify markers of malignant transformation and tumor progression.

EXPERIMENTAL DESIGN

Serial specimens of normal endometrium, simple hyperplasia, complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma obtained during a 10-year surveillance of DNA mismatch repair (MMR) gene mutation carriers (together 110 samples) were molecularly profiled and compared with a sporadic reference series of endometrial specimens taken for nonmalignant reasons (62 samples).

RESULTS

Among MMR gene mutation carriers, decreased MMR protein expression was present in 7% in normal endometrium, 40% in simple hyperplasia, 100% in complex hyperplasia without atypia, 92% in complex hyperplasia with atypia, and 100% in endometrial carcinoma. Microsatellite instability frequencies were lower (6%, 17%, 67%, 38%, and 64%, respectively). Among 24 tumor suppressor genes, the number of methylated loci increased from normal endometrium to simple hyperplasia to complex hyperplasia (complex hyperplasia without atypia/complex hyperplasia with atypia) in both Lynch syndrome and reference series. The most frequently methylated genes were CDH13, RASSF1A, and GSTP1. In MMR gene mutation carriers, MMR and methylation defects appeared up to 12 years before endometrial carcinoma.

CONCLUSIONS

Molecular changes in endometrial tissue are detectable several years before endometrial carcinoma in genetically predisposed individuals. Abnormal MMR and methylation classify normal endometrium and simple hyperplasia into one category and complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma into another, suggesting that, contrary to a traditional view, complex hyperplasia without atypia and complex hyperplasia with atypia are equally important as precursor lesions of endometrial carcinoma.

Lynch syndrome and related familial colorectal cancers

Lynch syndrome (hereditary non-polyposis colorectal cancer, HNPCC) refers to autosomal dominant predisposition to colorectal, endometrial, and a spectrum of other cancers. The syndrome is due to heterozygous germ line mutations in one of the mismatch repair genes MLH1, MSH2, MSH6, and PMS2. Amsterdam I and II criteria for clinical diagnosis and Bethesda guidelines for molecular testing of suspected patients usually point out additional families in which there is no evidence of mismatch repair deficiency even after screening by microsatellite instability analysis and/or immunohistochemistry for mismatch repair proteins. Hence, the term "Lynch syndrome" should be restricted to those families with germ line mutations in one of the mismatch repair genes. Familial colorectal tumors with no evidence of mismatch repair deficiency were shown to be clinically and molecularly distinct from classical Lynch syndrome tumors and, therefore, were designated "familial colorectal cancer type X" (FCC-X). The predisposing gene(s) to FCC-X is as yet unknown, but extensive research is currently underway to delineate its etiology. Given the above distinctions, the term hereditary nonpolyposis colorectal cancer (HNPCC), which was formerly used to refer to clinically diagnosed colorectal cancer families that might or might not have mismatch repair deficiency, is being replaced by one of the more informative names: Lynch syndrome and FCC-X.

Cutaneous T-cell lymphoma-associated lung cancers show chromosomal aberrations differing from primary lung cancer

Cutaneous T-cell lymphoma (CTCL) patients have an increased risk of certain secondary cancers, the most common of which are lung cancers, especially small cell lung cancer. To reveal the molecular pathogenesis underlying CTCL-associated lung cancer, we analyzed genomic aberrations in CTCL-associated and reference lung cancer samples. DNA derived from microdissected lung cancer cells of five CTCL-associated lung cancers and five reference lung cancers without CTCL association was analyzed by comparative genomic hybridization (CGH). Fluorescent in situ hybridization (FISH), immunohistochemistry (IHC), and loss of heterozygosity (LOH) analysis were performed for selected genes. In CTCL-associated lung cancer, CGH revealed chromosomal aberrations characterizing both lung cancer and CTCL, but also losses of 1p, and 19, and gains of 4q and 7, hallmarks of CTCL. LOH for the CTCL-associated NAV3 gene was detected in two of the four informative primary lung cancers. FISH revealed increased copy number of the KIT gene in 3/4 of CTCL-associated lung cancers and 1/5 of primary lung cancers. PDGFRA and VEGFR2 copy numbers were also increased. IHC showed moderate KIT expression when the gene copy number was increased. CTCL-associated lung cancer shows chromosomal aberrations different from primary lung cancer, especially amplifications of 4q, a chromosome arm frequently deleted in the latter tumor type. Copy numbers and expression of selected genes in chromosome 4 differed between CTCL-associated and reference lung cancers. These preliminary observations warrant further prospective studies to identify the common underlying factors between CTCL and CTCL-associated lung cancer.

Epigenetic signatures of familial cancer are characteristic of tumor type and family category

Tumor suppressor genes (TSG) may be inactivated by methylation of critical CpG sites in their promoter regions, providing targets for early detection and prevention. Although sporadic cancers, especially colorectal carcinoma (CRC), have been characterized for epigenetic changes extensively, such information in familial/hereditary cancer is limited. We studied 108 CRCs and 63 endometrial carcinomas (EC) occurring as part of hereditary nonpolyposis CRC, as separate familial site-specific entities or sporadically, for promoter methylation of 24 TSGs. Eleven genes in CRC and 6 in EC were methylated in at least 15% of tumors and together accounted for 89% and 82% of promoter methylation events in CRC and EC, respectively. Some genes (e.g., CDH13, APC, GSTP1, and TIMP3) showed frequent methylation in both cancers, whereas promoter methylation of ESR1, CHFR, and RARB was typical of CRC and that of RASSF1(A) characterized EC. Among CRCs, sets of genes with methylation characteristic of familial versus sporadic tumors appeared. A TSG methylator phenotype (methylation of at least 5 of 24 genes) occurred in 37% of CRC and 18% of EC (P = 0.013), and the presence versus absence of MLH1 methylation divided the tumors into high versus low methylation groups. In conclusion, inactivation of TSGs by promoter methylation followed patterns characteristic of tumor type (CRC versus EC) and family category and was strongly influenced by MLH1 promoter methylation status in all categories. Paired normal tissues or blood displayed negligible methylation arguing against a constitutional methylation abnormality in familial cases.

Differential cancer predisposition in Lynch syndrome: insights from molecular analysis of brain and urinary tract tumors

Hereditary non-polyposis colorectal carcinoma (Lynch syndrome) is among the most common hereditary cancers in man and a model of cancers arising through deficient DNA mismatch repair (MMR). Lynch syndrome patients are predisposed to different cancers in a non-random fashion, the basis of which is poorly understood. We addressed this issue by determining the molecular profiles for different tumors from a nationwide cohort of Lynch syndrome families (approximately 150 tumors in total). We focused on some less prevalent cancers, affecting the brain (n = 7) and urinary tract (five bladder and five ureter uroepithelial cancers and four kidney adenocarcinomas), and compared their molecular characteristics to those of the most common cancers, colorectal, gastric and endometrial adenocarcinomas, from the same families. Despite origin from verified MMR gene mutation carriers, the frequency of high-level microsatellite instability in tumors varied between high (100-96% for ureter, stomach and colon), intermediate (63-60% for endometrium and bladder) and low (25-0% for kidney and brain). In contrast to gastrointestinal and endometrial carcinomas, active (nuclear) beta-catenin was rare and KRAS mutations were absent in brain and urological tumors. Compared with other tumors, frequent stabilization of p53 protein characterized urinary tract cancers. Promoter methylation of tumor suppressor genes discriminated the tumors in an organ-specific manner. Our findings suggest that different Lynch syndrome tumors develop along different routes. Uroepithelial cancers of the ureter (and bladder to lesser extent) share many characteristics of MMR deficiency-driven tumorigenesis, whereas brain tumors and kidney adenocarcinomas follow separate pathways.

Somatic FGF9 mutations in colorectal and endometrial carcinomas associated with membranous beta-catenin

We previously described striking molecular features including high frequency of membranous beta-catenin in subsets of familial colon cancers with as yet unknown predisposition. We hypothesized that such tumors might carry mutations in Wnt/beta-catenin target genes. Fibroblast growth factor 9 (FGF9) was an attractive target, as it maps to a common area of loss of heterozygosity (LOH) in colorectal carcinomas on 13q12.11. Here, we report, for the first time, the occurrence of FGF9 mutations in human cancers. We found a total of six distinct FGF9 mutations including one frameshift, four missense, and one nonsense, in 10 (six colorectal and four endometrial) out of 203 tumors and cell lines. The frameshift mutation was detected in five different tumors. Mapping of these mutations onto the crystal structure of FGF9 predicted that they should all lead to loss of function albeit through variable mechanisms. The p.R173K mutation should diminish ligand affinity for heparin/heparan sulfate, the p.V192M, p.D203G, and p.L188YfsX18 (FGF9(Delta205-208)) mutations should negatively impact ligand's interaction with receptor, while p.G84E and p.E142X (FGF9(Delta142-208)) mutations should interfere with ligand folding. Consistent with these structural predictions, the p.V192M, p.D203G, and p.L188YfsX18 (FGF9(Delta205-208)) mutations impaired the ability of ligand to activate mitogen-activated protein kinase (MAPK) cascade in cultured cells expressing FGF receptors. LOH was observed in seven out of nine FGF9 mutant tumors, supporting the predicted loss of function. Interestingly, eight out of 10 (80%) of the FGF9 mutant tumors showed normal membranous beta-catenin expression and the absence of mutation in the beta-catenin gene (CTNNB1). These data suggest that FGF9 plays a role in colorectal and endometrial carcinogenesis.

Truncation of MBD4 predisposes to reciprocal chromosomal translocations and alters the response to therapeutic agents in colon cancer cells

We previously identified a novel genomic instability phenotype of multiple reciprocal chromosomal translocations in a MLH1-defective, microsatellite unstable (MSI) colon cancer cell line (HCA7) and, further, showed that it was unlikely to be directly caused by the mismatch repair (MMR) defect in this cell line. To gain insight into the molecular basis to this novel translocation phenotype, we examined coding and splice-site nucleotide repeat tracts in DNA repair genes for mutations by direct sequencing together with RT-PCR expression analysis of the associated transcript. The material was a selected panel of 8 MSI cell lines including HCA7. A strong candidate identified through this approach was MBD4 as it showed a homozygous truncating mutation associated with substantial loss of the transcript in HCA7 not seen in the other lines. In previous published studies, heterozygous MBD4 mutations were observed in up to 89% of sporadic MSI microdissected colon tumor foci. Using MFISH, we show that over-expression of the truncated MBD4 (+MBD4(tru)) in DLD1, a MSH6 defective, MSI human colon carcinoma cell line predisposed these cells to acquire structural chromosomal rearrangements including multiple reciprocal translocations after irradiation, reminiscent of those seen in HCA7. We also show that over-expression of MBD4(tru) in DLD1 alters the colony survival after exposure to cisplatin or etoposide. These data suggest a wide role for MBD4 in DNA damage response and maintaining chromosomal stability.

Patterns of PIK3CA alterations in familial colorectal and endometrial carcinoma

While the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is known to be activated in multiple sporadic cancers, the role of this pathway in familial tumors is mostly unknown. We searched for alterations in the catalytic domain of PI3K (PIK3CA), PTEN and KRAS, all of which may contribute to PI3K/AKT pathway activation, in a total of 160-familial colorectal (CRC) and endometrial carcinomas (EC), stratified by the presence vs. absence of germline mutations in DNA mismatch repair (MMR) genes. PIK3CA alterations (consisting of point mutations or low-level amplification, which were mutually exclusive with 1 exception) occurred in 10/70 (14%) of CRCs and 19/90 (21%) of ECs. Within ECs, amplification was significantly associated with the subgroup lacking germline mutations in MMR genes (familial site-specific endometrial cancer) (p = 0.015). Decreased or lost PTEN expression was characteristic of endometrial tumourigenesis (51/81, 63%, in EC compared with 24/62, 39%, in CRC, p = 0.004) and KRAS mutations of colorectal tumourigenesis (19/70, 27% in CRC vs. 9/89, 10%, in EC, p = 0.006) regardless of the MMR gene mutation status. PIK3CA alterations frequently coexisted with PTEN or KRAS changes. Combined with published studies on sporadic tumors, our data broaden the understanding of the role for PI3K pathway genes in human tumorigenesis.

Is gastric cancer part of the tumour spectrum of hereditary non-polyposis colorectal cancer? A molecular genetic study

BACKGROUND

Gastric cancer is the second most common extracolonic malignancy in individuals with hereditary non-polyposis colorectal cancer (HNPCC)/Lynch syndrome. As gastric cancer is relatively common in the general population as well, it is not clear whether or not gastric cancer is a true HNPCC spectrum malignancy.

AIM

To determine whether or not gastric cancer is a true HNPCC spectrum malignancy.

SUBJECTS AND METHODS

The molecular and clinicopathological profiles of gastric cancers (n = 13) from HNPCC mutation carriers were evaluated and compared with the profiles of sporadic gastric cancers (n = 46) stratified by histology and microsatellite instability (MSI) status.

RESULTS

This study on sporadic and HNPCC gastric cancers revealed several important universal associations. Loss of heterozygosity in the adenomatous polyposis coli (APC) region was associated with intestinal histology regardless of the MSI (p = 0.007). KRAS-mutations (p = 0.019) and frameshift mutations in repeat tracts of growth-regulatory genes (p<0.001) were associated with MSI tumours being absent in microsatellite stable (MSS) tumours. The average number of methylated tumour suppressor gene loci among the 24 genes studied (methylation index) was higher in MSI than in MSS tumours regardless of histology (p<0.001). Gastric cancers from HNPCC mutation carriers resembled sporadic intestinal MSI gastric cancers, except that MLH1 promoter methylation was absent (p<0.001) and the general methylation index was lower (p = 0.038), suggesting similar, but not identical, developmental pathways. All these lacked the mismatch repair protein corresponding to the germline mutation and displayed high MSI.

CONCLUSION

The present molecular evidence, combined with the previous demonstration of an increased incidence relative to the general population, justify considering gastric cancers as true HNPCC spectrum malignancies.

Mechanisms of inactivation of MLH1 in hereditary nonpolyposis colorectal carcinoma: a novel approach

Mutations in the DNA mismatch repair gene MLH1 are a major cause of hereditary nonpolyposis colorectal cancer (HNPCC). No mutant phenotype is observed before the wild-type (wt) allele is somatically inactivated in target tissue. We addressed the mechanisms of MLH1 inactivation in 25 colorectal (CRC) and 32 endometrial cancers (ECs) from MLH1 mutation carriers (Mut1, in-frame genomic deletion; Mut2, out-of-frame splice site mutation; Mut3, missense mutation). By a quantitative method, matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF), utilizing four intragenic single nucleotide polymorphisms and mutations, loss of heterozygosity (LOH) was present in 31/57 (54.4%) of tumors. The wt allele displayed LOH more often than the mutant allele (23/57 vs 8/57, P=0.006). For Mut1, LOH was more frequent in CRC than EC (10/11 vs 1/13, P<0.0001), whereas Mut2 and Mut3 displayed opposite LOH pattern. Moreover, although wt LOH predominated in CRC irrespective of the predisposing mutation, LOH often affected the mutant allele in EC from Mut2 and Mut3 carriers (6/19, 31.6%). MLH1 promoter methylation, which reflected a more widespread hypermethylation tendency, occurred in 4/55 (7.3%) of tumors and was inversely associated with LOH. In conclusion, the patterns of somatic events (LOH and promoter methylation) differ depending on the tissue and germline mutation, which may in part explain the differential tumor susceptibility of different organs in HNPCC. MALDI-TOF provides a novel approach for the detection and quantification of LOH.

The genetics of HNPCC: application to diagnosis and screening

Hereditary nonpolyposis colorectal cancer syndrome (HNPCC; Lynch Syndrome) is the most common form of hereditary colorectal cancers. Predisposed individuals have increased lifetime risk of developing colorectal, endometrial and other cancers. The syndrome is primarily due to heterozygous germline mutations in one of the mismatch repair genes; mainly MLH1, MSH2, MSH6 and PMS2. The resulting mismatch repair deficiency leads to microsatellite instability which is the hallmark of tumors arising within this syndrome, as well as a variable proportion of sporadic tumors. Diagnostic guidelines and criteria for molecular testing of suspected families have been proposed and are continuously updated. However, not all families fulfilling these criteria show mutations in mismatch repair genes and/or microsatellite instability implicating other, as yet unknown, carcinogenic mechanisms and predisposition genes. This subset of tumors is the focus of current clinical and molecular research. This review addresses recent advances in the field of HNPCC research and their applications in the management of affected individuals and families.

Adenomatous polyposis families that screen APC mutation-negative by conventional methods are genetically heterogeneous

PURPOSE

One third of families with classical adenomatous polyposis (FAP), and a majority of those with attenuated FAP (AFAP), remain APC mutation-negative by conventional methods. Our purpose was to clarify the genetic basis of polyposis and genotype-phenotype correlations in such families.

PATIENTS AND METHODS

We studied a cohort of 29 adenomatous polyposis families that had screened APC mutation-negative by the protein truncation test, heteroduplex analysis, and exon-specific sequencing. The APC gene was investigated for large genomic rearrangements by multiplex ligation-dependent probe amplification (MLPA), and for allelic mRNA expression by single nucleotide primer extension (SNuPE). The AXIN2 gene was screened for mutations by sequencing.

RESULTS

Four families (14%) showed a constitutional deletion of the entire APC gene (three families) or a single exon (one family). Seven families (24%) revealed reduced or extinct mRNA expression from one APC allele in blood, accompanied by loss of heterozygosity in the APC region in six (75%) of eight tumors. In 15 families (52%), possible APC involvement could be neither confirmed nor excluded. Finally, as detailed elsewhere, three families (10%) had germline mutations in genes other than APC, AXIN2 in one family, and MYH in two families.

CONCLUSION

"APC mutation-negative" FAP is genetically heterogeneous, and a combination of MLPA and SNuPE is able to link a considerable proportion (38%) to APC. Significant differences were observed in clinical manifestations between subgroups, emphasizing the importance of accurate genetic and clinical characterization for the proper management of such families.

APC and beta-catenin protein expression patterns in HNPCC-related endometrial and colorectal cancers

OBJECTIVE

The adenomatous polyposis coli (APC) and beta-catenin (CTNNB1) genes are the two major components of the Wnt signaling pathway that has been shown to play an important role in the formation of certain cancers. The overactivation of the pathway, which results in abnormal accumulation of beta-catenin protein in nuclei, contributes to most colorectal cancers (CRCs), both sporadic and hereditary, as well as sporadic endometrial cancers (ECs). Here, we studied the involvement of APC and beta-catenin in hereditary nonpolyposis colorectal cancer (HNPCC)-related ECs, and compared the expression patterns to those in HNPCC-related CRCs.

MATERIALS AND METHODS

Nineteen ECs and 31 CRCs derived from HNPCC patients were immunohistochemically stained with anti-APC- and anti-beta-catenin-antibodies.

RESULTS

Tumor-specific loss of APC was observed in 16 of endometrial cancers (3 of 19) and in 39 of colorectal cancers (12 of 31). Consistently, the loss of APC expression was associated with nuclear beta-catenin staining. Altogether, aberrant beta-catenin localization was observed in 53 of ECs (10 of 19) as compared to 84 of CRCs (26 of 31) (P=0.02).

CONCLUSION

Our results suggest a frequent overactivation of the Wnt signaling pathway in hereditary endometrial cancer. In accordance with studies on sporadic cancers, abnormal accumulation of beta-catenin protein in nuclei occurred much less frequently in HNPCC-related ECs than CRCs, which may reflect organ-specific differences in their pathogenesis.

Molecular analysis of familial endometrial carcinoma: a manifestation of hereditary nonpolyposis colorectal cancer or a separate syndrome?

PURPOSE

Familial clustering of endometrial carcinoma (EC) may occur as part of hereditary nonpolyposis colorectal cancer (HNPCC), a multiorgan cancer syndrome with mismatch repair (MMR) deficiency. Clustering of EC alone, termed as familial site-specific EC, may constitute a separate entity. Because its genetic basis is unknown, our purpose was to characterize such families molecularly.

MATERIALS AND METHODS

Twenty-three families with site-specific EC were identified among 519 consecutive patients diagnosed with EC during 1986 to 1997. Tumor tissues were examined for MMR protein expression by immunohistochemical (IHC) analysis, and MMR genes pinpointed by IHC changes were screened for germline mutations by exon-by-exon sequencing, multiplex ligation-dependent probe amplification, and direct tests for mutations common in the population.

RESULTS

Among 33 ECs from 23 families, MLH1 protein was lost in seven tumors (21%), MSH2 together with MSH6 was lost in four tumors (12%), and MSH6 alone was lost in five tumors (15%). A truncating germline mutation in MSH6 (3261insC) was identified in one family and a likely pathogenic missense mutation in MSH2 (D603N) was identified in another family. Among the original 519 patients, nine (all with colon cancer in the family) were diagnosed with HNPCC at the outset-six with MLH1 and three with MSH2 mutations.

CONCLUSION

Our study gives a minimum overall frequency of 2.1% (11 of 519) for germline MMR defects ascertained through EC in the index patients. The fact that only two of 23 families with site-specific EC (8.7%) had germline mutations in MMR genes suggests another as yet unknown etiology in most families with site-specific EC.

Comprehensive characterization of HNPCC-related colorectal cancers reveals striking molecular features in families with no germline mismatch repair gene mutations

A considerable fraction of families with HNPCC shows no germline mismatch repair (MMR) gene mutations. We previously detected 'hidden' MMR gene defects in 42% of such families, leaving the remaining 58% 'truly' mutation negative. Here, we characterized 50 colorectal carcinomas and five adenomas arising in HNPCC families; 24 truly MMR gene mutation negative and 31 MMR gene mutation positive. Among 31 tumors from MMR gene mutation positive families, 25 (81%) had active Wnt signaling as indicated by aberrant beta-catenin localization with or without CTNNB1 mutations, compared to only 7/18 tumors from MMR gene mutation negative families (39%; P=0.005). CGH studies revealed stable profiles in 9/16 (56%) of MMR gene mutation negative tumors, which was significantly associated with membranous beta-catenin (P=0.005). Tumors with membranous beta-catenin from the MMR gene mutation negative group also showed low frequency of TP53 mutations compared to those with nuclear beta-catenin. Thus, a majority of the MMR gene mutation negative cases exhibited a novel molecular pattern characterized by the paucity of changes in common pathways to colorectal carcinogenesis. This feature distinguishes the MMR gene mutation negative families from both HNPCC families linked to MMR defects and sporadic cases, suggesting the involvement of novel predisposition genes and pathways in such families.

Restoring mismatch repair does not stop the formation of reciprocal translocations in the colon cancer cell line HCA7 but further destabilizes chromosome number

An important anticarcinogenic function of the mismatch repair (MMR) system is its role in preventing recombination between similar, but nonidentical (homeologous) sequences, thus preventing chromosomal rearrangements. We recently identified a novel chromosomal instability (CIN) phenotype in an MMR defective colon cancer cell line (HCA7) characterized by an ongoing tendency to multiple reciprocal chromosomal translocations. To analyse the relation between MMR and chromosomal changes more closely, the HCA7 stem clone was divided into three stocks. The first was stably transfected with MLH1 expression plasmid, the second was regularly exposed to the demethylating agent 5-azacytidin to re-express the hypermethylated MLH1 gene, and the third was an unmanipulated control stock. All stocks were propagated in vitro for 55-80 passages and, furthermore, some of the early passages were irradiated to induce DNA double-strand breaks. Multiplex-fluorescent in situ hybridization (M-FISH) analysis showed that all three stocks acquired varying numbers of reciprocal translocations and other structural changes at some point. Interestingly, the control stock, which is MMR defective, maintained its numerical chromosomal stability, while some of the MMR-proficient clones showed additional numerical instability. Although the control stock was less sensitive to irradiation, its surviving clones showed marked stability of chromosome structure and number compared to the MMR-competent stocks. These results show that restoring MMR does not prevent the development of reciprocal translocations but rather predisposes cells to numerical CIN after irradiation. Thus, the accumulating data suggest that MMR defect may not be necessary for the development of reciprocal chromosomal translocations but might be permissive.

HNPCC mutation MLH1 P648S makes the functional protein unstable, and homozygosity predisposes to mild neurofibromatosis type 1

Heterozygous germ-line mutations in DNA mismatch repair (MMR) genes predispose individuals to hereditary nonpolyposis colorectal cancer (HNPCC), whereas with homozygous MMR gene mutations children are diagnosed at an early age with de novo neurofibromatosis type 1 (NF1) and/or hematological malignancies. Here, we describe a mutation, MLH1 P648S, which was found in a typical HNPCC family, with one homozygous child displaying mild features of NF1 and no hematological cancers. To evaluate the pathogenicity of the mutation, we studied both the expression and the function of the mutated protein. It generally has been assumed that the predisposing mutations prevent the production of a functional protein. The mutated MLH1 P648S protein was found to be unstable but still functional in mismatch repair, suggesting that the cancer susceptibility in the family and possibly also the mild disease phenotype in the homozygous individual are linked to shortage of the functional protein.

Molecular basis and diagnostics of hereditary colorectal cancers

Hereditary colorectal cancer syndromes are classified according to the presence of unusually large number of adenomatous or hamartomatous polyps, or their absence. The latter category includes hereditary non-polyposis colorectal cancer (Lynch syndrome) and its variants Muir-Torre and Turcot's syndromes. Adenomatous polyposis syndromes include familial adenomatous polyposis (FAP) and its variants, and the recently identified MYH- (mutY homolog)-associated polyposis. Hamartomatous polyposis syndromes include juvenile polyposis, Peutz-Jeghers syndrome, and Cowden syndrome, which is now included within the broader category 'PTEN (phosphatase and tensin homolog) hamartoma tumour syndrome'. Other syndromes such as the 'hereditary breast and colon cancer' and 'familial colorectal cancer' are not yet fully characterized. This review addresses the molecular basis of these syndromes with particular reference to the recent advances in this rapidly progressive field and the applications of such knowledge in diagnosis and management.