Exportin-5 Functions as an Oncogene and a Potential Therapeutic Target in Colorectal Cancer

Purpose: Dysregulated expression of miRNAs has emerged as a hallmark feature in human cancers. Exportin-5 (XPO5), a karyopherin family member, is a key protein responsible for transporting precursor miRNAs from the nucleus to the cytoplasm. Although XPO5 is one of the key regulators of miRNA biogenesis, its functional role and potential clinical significance in colorectal cancer remains unclear.Experimental Design: The expression levels of XPO5 were initially assessed in three genomic datasets, followed by determination and validation of the relationship between XPO5 expression and clinicopathologic features in two independent colorectal cancer patient cohorts. A functional characterization of XPO5 in colorectal cancer was examined by targeted gene silencing in colorectal cancer cell lines and a xenograft animal model.Results: XPO5 is upregulated, both at mRNA and protein levels, in colorectal cancers compared with normal tissues. High XPO5 expression is associated with worse clinicopathologic features and poor survival in colorectal cancer patient cohorts. The siRNA knockdown of XPO5 resulted in reduced cellular proliferation, attenuated invasion, induction of G₁-S cell-cycle arrest, and downregulation of key oncogenic miRNAs in colorectal cancer cells. These findings were confirmed in a xenograft animal model, wherein silencing of XPO5 resulted in the attenuation of tumor growth.Conclusions: XPO5 acts like an oncogene in colorectal cancer by regulating the expression of miRNAs and may be a potential therapeutic target in colorectal cancer. Clin Cancer Res; 23(5); 1312-22. ©2016 AACR.

Celecoxib for the Prevention of Colorectal Adenomas: Results of a Suspended Randomized Controlled Trial

BACKGROUND

Cyclooxygenase (COX)-2 inhibitors such as celecoxib were designed to preserve anti-inflammatory activity without inhibiting COX-1. Downregulation of COX-2 inhibits colorectal carcinogenesis.

METHODS

The Selenium and Celecoxib Trial was a randomized, placebo-controlled trial of once-daily selenium 200 µg and celecoxib 400 mg, alone or together, for colorectal adenoma prevention. Men and women between age 40 and 80 years were eligible following colonoscopic removal of adenomas. The primary outcome was development of new adenomas. Celecoxib was suspended early because of cardiovascular toxicity in other trials. Accrual to selenium or placebo continued. Before suspension, 824 participants were randomly assigned to celecoxib or placebo, of whom 712 (86.4%) were available for analysis. All statistical tests were two-sided.

RESULTS

In the placebo and celecoxib arms of 356 participants each, adenoma detection was 47.5% and 49.7% (relative risk [RR] = 1.04, 95% confidence interval [CI] = 0.90 to 1.21, P = .58), respectively, after median periods of 13.6 and 14.2 months on intervention. Among participants colonoscoped within 12 months of discontinuing intervention (n = 244), overall adenoma recurrence (RR = 0.69, 95% CI = 0.48 to 0.98, P = .04) and recurrence with advanced adenomas (RR = 0.23, 95% CI = 0.07 to 0.80, P = .02) were reduced with celecoxib. Reduction of adenoma recurrence was greatest in participants with previous advanced adenomas. Celecoxib increased risk of hypertension in participants with pre-existing cardiovascular risk factors compared with placebo (hazard ratio = 2.19, 95% CI = 1.07 to 4.50, P = .03).

CONCLUSIONS

Limited-duration celecoxib prevents adenoma recurrence in patients with prior high-risk adenomas, in whom strategies to minimize cardiovascular toxicity might be feasible.

Selenium Supplementation for Prevention of Colorectal Adenomas and Risk of Associated Type 2 Diabetes

BACKGROUND

Selenium supplementation may help to prevent colorectal cancer; as precursors of colorectal cancer, colorectal adenomas are a surrogate for colorectal cancer. Selenium supplementation may increase risk of type 2 diabetes (T2D).

METHODS

The Selenium and Celecoxib (Sel/Cel) Trial was a randomized, placebo controlled trial of selenium 200 µg daily as selenized yeast and celecoxib 400 mg once daily, alone or together, for colorectal adenoma prevention. Men and women between age 40 and 80 years were eligible following colonoscopic removal of colorectal adenomas. The primary outcome was adenoma development. Celecoxib was suspended because of cardiovascular toxicity in other trials, but accrual continued to selenium and placebo. A total of 1621 participants were randomly assigned to selenium or placebo, of whom 1374 (84.8%) were available for analysis. All statistical tests were two-sided.

RESULTS

In the respective placebo and selenium arms of 689 and 685 participants, adenoma detection after medians of 33.6 (range = 0.0-85.1 months) and 33.0 months (range = 0.0-82.6 months) were 42.8% and 44.1% (relative risk [RR] = 1.03, 95% confidence interval [CI] = 0.91 to 1.16, P = .68). In participants with baseline advanced adenomas, adenoma recurrence was reduced by 18% with selenium (RR = 0.82, 95% CI = 0.71 to 0.96, P = .01). In participants receiving selenium, the hazard ratio for new-onset T2D was 1.25 (95% CI = 0.74 to 2.11, P = .41), with a statistically significantly increased risk of selenium-associated T2D among older participants (RR = 2.21; 95% CI = 1.04 to 4.67, P = .03).

CONCLUSIONS

Overall, selenium did not prevent colorectal adenomas and showed only modest benefit in patients with baseline advanced adenomas. With limited benefit and similar increases in T2D to other trials, selenium is not recommended for preventing colorectal adenomas in selenium-replete individuals.

Abstract 952: Genome-wide enhancer analysis identifies PVT1 as an oncogenic enhancer of MYC

Introduction: An enhancer is a short stretch of DNA that can be targeted by specific proteins to activate gene transcription, and recent evidence suggests that enhancers can act as key regulators of oncogenes in cancer. Recently, the FANTOM5 project comprehensively characterized enhancer activities in various cell types. Interestingly, several enhancers coding for lncRNAs were commonly up-regulated in multiple cancer types, suggesting that these enhancers may play an important oncogenic role through enhancer-promoter-lncRNA interaction, and may help mediate chemoresistance. However, specific lncRNAs with oncogenic enhancer function and their clinical significance in colorectal cancer (CRC) remains unexplored.

Aims: We analyzed genome-wide cancer-specific enhancer activation in multiple cancers to identify potential oncogenic lncRNAs, and assessed their clinical significance in two independent patient cohorts with CRC. We thereafter evaluated the functional role of candidate enhancer lncRNAs in CRC.

Methods: Using the FANTOM5 enhancer database, cancer-specific enhancer activity was analyzed in cancers of the colon, stomach, lung, prostate and melanoma. LncRNA candidates that encode these cancer-specific enhancers were identified. We then screened these lncRNAs in two independent CRC cohorts, as well as the APC(Min/+) mouse model. The functional role of target lncRNAs was assessed in parental and chemoresistant CRC cell lines. The oncogenic enhancer activity was confirmed using the chromatin conformation capture (3C) assay.

Results: We identified ten lncRNA candidates with consistent enhancer activities in all five cancer types. In particular, PVT1 appeared to have one of the highest enhancer activities. Using two independent CRC cohorts, we confirmed upregulation of PVT1 in cancer tissues. Patients with high-PVT1 expression had shorter overall survival in Stage II and III CRCs, suggesting that the PVT1 expression could discriminate high-risk patients, and identify those who may benefit from adjuvant chemotherapy. Intriguingly, we discovered that PVT1 was also upregulated in human colorectal adenomas as well as adenomas isolated from APC(Min/+) mice, indicating that PVT1 may be involved in the early stages of the adenoma-carcinoma sequence. The expression level of PVT1 significantly correlated with c-MYC expression in CRC specimens and the 3C assay showed that the enhancer region in PVT1 can target c-MYC. Finally, we demonstrated that PVT1 and c-MYC were co-overexpressed in several chemoresistant CRC cell lines, and that suppression of PVT1 led to a significant reduction in proliferation of chemoresistant cells, further suggesting that PVT1 may play a key role in chemoresistance.

Conclusion: PVT1 acts as an oncogenic enhancer of c-MYC in CRC. High expression of PVT1 served as a predictive marker for identifying high-risk Stage II and III CRC patients. PVT1 could serve as a potential therapeutic target in chemoresistant CRCs.

Citation Format: Kunitoshi Shigeyasu, Shusuke Toden, Takeshi Nagasaka, Toshiyoshi Fujiwara, C. Richard Boland, Ajay Goel. Genome-wide enhancer analysis identifies PVT1 as an oncogenic enhancer of MYC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 952.

Microsatellite Alterations With Allelic Loss at 9p24.2 Signify Less-Aggressive Colorectal Cancer Metastasis

BACKGROUND & AIMS

Molecular events that lead to recurrence and/or metastasis after curative treatment of patients with colorectal cancers (CRCs) are poorly understood. Patients with stage II or III primary CRC with elevated microsatellite alterations at selected tetranucleotide repeats and low levels of microsatellite instability (E/L) are more likely to have disease recurrence after treatment. Hypoxia and/or inflammation not only promote metastasis, but also induce elevated microsatellite alterations at selected tetranucleotide repeats by causing deficiency of MSH3 in the cancer cell nucleus. We aimed to identify genetic alterations associated with metastasis of primary colorectal tumors to liver and to determine their effects on survival.

METHODS

We obtained 4 sets of primary colorectal tumors and matched liver metastases from hospitals in Korea and Japan. Intragenic microsatellites with large repeats at 141 loci were examined for frame-shift mutations and/or loss of heterozygosity (LOH) as possible consequences of MSH3 deficiency. Highly altered loci were examined for association with E/L in liver metastases. We analyzed data from 156 of the patients with stage II or III primary colorectal tumors to determine outcomes and whether altered loci were associated with E/L.

RESULTS

LOH at several loci at chromosome 9p24.2 (9p24.2-LOH) was associated with E/L in liver metastases (odds ratio = 10.5; 95% confidence interval: 2.69-40.80; P = .0007). We found no significant difference in the frequency of E/L, 9p24.2-LOH, mutations in KRAS or BRAF, or the combination of E/L and 9p24.2-LOH, between primary colorectal tumors and their matched metastases. Patients with stage II or III colorectal tumors with E/L and 9p24.2-LOH had increased survival after CRC recurrence (hazard ratio = 0.25; 95% CI: 0.12-0.50; P = .0001), compared with patients without with E/L and 9p24.2-LOH. E/L with 9p24.2-LOH appeared to be an independent prognostic factor for overall survival of patients with stage III CRC (hazard ratio = 0.06; 95% CI: 0.01-0.57; P = .01).

CONCLUSIONS

E/L with 9p24-LOH appears to be a biomarker for less aggressive metastasis from stage III primary colorectal tumors.

Defective DNA mismatch repair activity is common in sebaceous neoplasms, and may be an ineffective approach to screen for Lynch syndrome

A subset of individuals with Lynch syndrome (LS) has a variant called Muir-Torre syndrome (MTS) where patients develop multiple sebaceous neoplasms. Absence of gene expression and microsatellite instability (MSI) have been welldocumented in LS neoplasms. It is unclear whether the presence of these abnormalities in isolated sebaceous neoplasms would indicate the likely presence of otherwise unsuspected LS or MTS. 164 specimens of sporadic cutaneous sebaceous neoplasms were obtained. IHC was performed for expression of the DNA mismatch repair (MMR) genes MSH2 and MLH1. A 5-marker mononucleotide repeat microsatellite panel was analyzed to detect MSI, and two or more mutated markers were required for MSI. 164 sebaceous neoplasms were obtained from 162 patients. IHC data was successfully obtained from 162 samples and MSI data was obtained from 138 samples. 50/162 (31%) had abnormal IHC with loss of staining for either MSH2 (37/162, 23%), MLH1 (9/162, 5%) or both (4/162, 2%). 37% (52/138) of the tumors had MSI. 82% (111/136) of those with both IHC and MSI results correlated as expected. 18% (25/136) showed discordance between IHC and MSI. 69/163 (42%) had either abnormal IHC or MSI, indicating deficient DNA MMR activity. Given the substantial proportion of DNA MMR deficiency in these sebaceous neoplasms, screening for DNA MMR defects in sebaceous neoplasms would not appear to be an effective way to distinguish patients with LS or MTS from those with sporadic skin lesions and an ordinary risk of cancer.

Mutations of HNRNPA0 and WIF1 predispose members of a large family to multiple cancers

We studied a large family that presented a strong familial susceptibility to multiple early onset cancers including prostate, breast, colon, and several other uncommon cancers. Through targeted gene, linkage, and whole genome sequencing analyses, we show that the presence of a variant in the regulatory region of HNRNPA0 associated with elevated cancer incidence in this family (Hazard ratio = 7.20, p = 0.0004). Whole genome sequencing identified a second rare protein changing mutation of WIF1 that interacted with the HNRNPA0 variant resulting in extremely high risk for cancer in carriers of mutations in both genes (p = 1.98 × 10(-13)). Analysis of downstream targets of the mutations in these two genes showed that the HNRNPA0 mutation affected expression patterns in the PI3 kinase and ERK/MAPK signaling pathways, while the WIF1 variant influenced expression of genes that play a role in NAD biosynthesis. This is a first report of variation in HNRNPA0 influencing common cancers or of a striking interaction between rare variants coexisting in an extended pedigree and jointly affecting cancer risk.

Colonoscopy Surveillance After Colorectal Cancer Resection: Recommendations of the US Multi-Society Task Force on Colorectal Cancer

The US Multi-Society Task Force has developed updated recommendations to guide health care providers with the surveillance of patients after colorectal cancer (CRC) resection with curative intent. This document is based on a critical review of the literature regarding the role of colonoscopy, flexible sigmoidoscopy, endoscopic ultrasound, fecal testing and CT colonography in this setting. The document addresses the effect of surveillance, with focus on colonoscopy, on patient survival after CRC resection, the appropriate use and timing of colonoscopy for perioperative clearing and for postoperative prevention of metachronous CRC, specific considerations for the detection of local recurrence in the case of rectal cancer, as well as the place of CT colonography and fecal tests in post-CRC surveillance.

Colonoscopy Surveillance after Colorectal Cancer Resection: Recommendations of the US Multi-Society Task Force on Colorectal Cancer

The US Multi-Society Task Force has developed updated recommendations to guide health care providers with the surveillance of patients after colorectal cancer (CRC) resection with curative intent. This document is based on a critical review of the literature regarding the role of colonoscopy, flexible sigmoidoscopy, endoscopic ultrasound, fecal testing and CT colonography in this setting. The document addresses the effect of surveillance, with focus on colonoscopy, on patient survival after CRC resection, the appropriate use and timing of colonoscopy for perioperative clearing and for postoperative prevention of metachronous CRC, specific considerations for the detection of local recurrence in the case of rectal cancer, as well as the place of CT colonography and fecal tests in post-CRC surveillance.

Prognostic Subgroups among Patients with Stage II Colon Cancer

Colon cancer has traditionally been treated surgically. However, many cases of colon cancer are systemic at the time of diagnosis, and apparently curative surgery is followed at a later date by tumor recurrence as a consequence of circulating tumor cells before the surgery. Adjuvant medical therapies are designed to prevent recurrences after surgical resection. The current standard for clinical prognostication relies principally on pathological staging. In early-stage colon cancers (stages I and II), all the tumor is contained within the wall of the colon. Less than 10% of patients with stage I disease have a recurrence, and adjuvant chemotherapy is . . .

Active secretion of CXCL10 and CCL5 from colorectal cancer microenvironments associates with GranzymeB+ CD8+ T-cell infiltration

Transcriptional expression of CXCR3 and CCR5 cognate chemokines correlate with CD8⁺ T-cell infiltration and prolonged survival in colorectal cancer (CRC). These findings were derived mainly from paraffin embedded tissues; thus little is known about the secretion pattern of CD8⁺ T-cell targeting chemokines from CRCs. Therefore, we developed and introduced a novel platform that assesses the immune mediators that are secreted from live excised tissues. Transcriptional profiling and unsupervised hierarchical clustering of 43 CRCs based on expression of genes that represent the adaptive immune response were used to predict tumors that are strong secretors of T-cell targeting chemokines. Secretion of these mediators were corroborated using flow cytometric analysis of T-cell lineage markers: CD4, CD8, IFN-γ, and GzmB. We demonstrate that stronger secretion of CXCL10 (CXCR3 ligand) and CCL5 (CCR5 ligand) and infiltration of GzmB⁺CD8⁺ cytotoxic T-lymphocytes (CTLs) and IFN-γ⁺CD4⁺ helper T-cells can be predicted by transcriptional profiling, and that CRCs with stronger T-cell immunity were proportionally skewed towards early TNM stages and lacked distant organ metastasis. Our study represents the first functional analysis of secreted immune mediators from CRCs beyond immunohistochemistry and real-time PCR, and observed active physiological interactions between the tumor cells and the immune cells in the tumor microenvironment.

Genetics and Genetic Testing in Hereditary Colorectal Cancer

Colorectal cancer (CRC) remains the third most common cancer affecting men and women in the United States. Approximately one-third of CRCs are diagnosed in individuals who have family members also affected with the disease. Although the vast majority of colorectal neoplasms develop as a consequence of somatic genomic alterations arising in individual cells, approximately 5% of all CRCs arise in the setting of germline mutations in genes involved in key cellular processes. To date, multiple genes have been implicated in single-gene hereditary cancer syndromes, many of which are associated with increased risk for CRC, as well as other tumor types. This review outlines the clinical, pathologic, and genetic features of the hereditary cancer syndromes known to be associated with increased risk for CRC and delineates strategies for implementing genetic risk assessments in clinical settings.

Abstract 431: Active secretion of CXCL10 and CCL5 from colorectal cancer microenvironments associates with GranzymeB+ CD8+ T-cell infiltration

T-cell infiltration varies among colorectal tumors and directly impacts patient survival. Chemoattraction and infiltration of CD8+ T-cells are mediated by surface chemokine receptors CXCR3 and CCR5, and are associated with favorable prognosis. Transcriptional expression of these receptors’ cognate chemokines, as well as other inflammation-associated chemokines, correlate with prolonged disease-free survival (DFS). These findings, however, were derived from paraffin embedded tissues, thus little is known about the pattern of secreted T-cell targeting chemokines from colorectal tumors. Therefore, this investigation aimed to determine the secretion pattern of chemokines associated with DFS from immediately excised live tumor tissues. Our results demonstrate the first real functional analysis of chemokine activity in colorectal tumors beyond immunohistochemistry and real-time PCR. Forty-four colorectal tumors were procured immediately after surgery and categorized by transcriptional expression of two T-cell marker genes that represent the magnitude of type-1 T-cell activity. Tumors that more highly co-expressed IFNG and TBX21 consequently have a higher frequency of infiltrating GzmB+ CTLs and IFN-γ+ CD4+ helper T-cells and transcribe a unique pattern of DFS-associated chemokines when compared to normal mucosa. High co-expression of IFNG and TBX21 was bimodally distributed across the tumors collected. Tumors with higher co-expression more strongly secreted two DFS-associated chemokines, CXCR3 ligand, CXCL10 and CCR5 ligand, CCL5. Additional results demonstrate that tumors with higher co-expression are proportionally skewed towards early TMN stages and with mismatch repair-deficiency, confirming that infiltration of CD8+ T-cells are associated with early TNM stages and lack of metastasis. Secreted chemokines were detected using a novel immunoassay that may have implications for future development of immunopotentiating treatments in cancer.

Note: This abstract was not presented at the meeting.

Citation Format: Timothy J. Zumwalt, C. Richard Boland, Ajay Goel. Active secretion of CXCL10 and CCL5 from colorectal cancer microenvironments associates with GranzymeB+ CD8+ T-cell infiltration. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 431. doi:10.1158/1538-7445.AM2015-431

Serum miR-21, miR-29a, and miR-125b Are Promising Biomarkers for the Early Detection of Colorectal Neoplasia

PURPOSE

Circulating microRNAs (miRNA) are emerging as promising diagnostic biomarkers for colorectal cancer, but their usefulness for detecting early colorectal neoplasms remains unclear. This study aimed to identify serum miRNA biomarkers for the identification of patients with early colorectal neoplasms.

EXPERIMENTAL DESIGN

A cohort of 237 serum samples from 160 patients with early colorectal neoplasms (148 precancerous lesions and 12 cancers) and 77 healthy subjects was analyzed in a three-step approach that included a comprehensive literature review for published biomarkers, a screening phase, and a validation phase. RNA was extracted from sera, and levels of miRNAs were examined by real-time RT-PCR.

RESULTS

Nine miRNAs (miR-18a, miR-19a, miR-19b, miR-20a, miR-21, miR-24, miR-29a, miR-92, and miR-125b) were selected as candidate biomarkers for initial analysis. In the screening phase, serum levels of miR-21, miR-29a, and miR-125b were significantly higher in patients with early colorectal neoplasm than in healthy controls. Elevated levels of miR-21, miR-29a, and miR-125b were confirmed in the validation phase using an independent set of subjects. Area under the curve (AUC) values for serum miR-21, miR-29a, miR-125b, and their combined score in discriminating patients with early colorectal neoplasm from healthy controls were 0.706, 0.741, 0.806, and 0.827, respectively. Serum levels of miR-29a and miR-125b were significantly higher in patients who had only small colorectal neoplasms (≤5 mm) than in healthy subjects.

CONCLUSIONS

Because serum levels of miR-21, miR-29a, and miR-125b discriminated patients with early colorectal neoplasm from healthy controls, our data highlight the potential clinical use of these molecular signatures for noninvasive screening of patients with colorectal neoplasia.

MiR-320e is a novel prognostic biomarker in colorectal cancer

Background:

Advances in early detection and treatment have improved outcomes in patients with colorectal cancer (CRC). However, there remains a need for robust prognostic and predictive biomarkers. We conducted a systematic discovery and validation of microRNA (miRNA) biomarkers in two clinical trial cohorts of CRC patients.

Methods:

We performed an initial ‘discovery' phase using Affymetrix miRNA expression arrays to profile stage III CRC patients with and without tumour recurrence (n=50 per group) at 3-years of follow-up. All patients received adjuvant 5-fluorouracil (5-FU) plus oxaliplatin, that is, FOLFOX, treatment. During ‘validation', we analysed miRNAs using qRT–PCR in an independent cohort of 237 stage II–IV CRC patients treated with 5-FU-based chemotherapy, as well as in normal colonic mucosa from 20 healthy subjects. Association with disease recurrence, disease-free survival (DFS) and overall survival (OS) was examined using Cox proportional hazard models.

Results:

In the discovery cohort, miR-320e expression was significantly elevated in stage III colon cancers from patients with vs without recurrence (95% confidence interval (CI)=1.14–1.42; P<0.0001). These results were then independently validated in stage II and III tumours. Specifically, increased miR-320e expression was associated with poorer DFS (hazard ratio (HR)=1.65; 95% CI=1.27–2.13; P=0.0001) and OS (HR=1.78; 95% CI=1.31–2.41; P=0.0003) in stage III CRC patients.

Conclusions:

In two clinical trial cohorts, a systematic biomarker discovery and validation approach identified miR-320e to be a novel prognostic biomarker that is associated with adverse clinical outcome in stage III CRC patients treated with 5-FU-based adjuvant chemotherapy. These findings have important implications for the personalised management of CRC patients.

Novel Evidence for Curcumin and Boswellic Acid-Induced Chemoprevention through Regulation of miR-34a and miR-27a in Colorectal Cancer

Colorectal cancer is one of the most common causes of cancer-associated mortality worldwide, but it is truly a preventable disease. Both curcumin and boswellic acids are well-established dietary botanicals with potent antitumorigenic properties that have been shown to modulate multiple oncogenic pathways. Recent data suggest that the chemopreventive effects of these botanicals may, in part, be mediated through regulation of key cancer-related microRNAs (miRNA) and their downstream gene targets. Here, we investigated the antitumorigenic effects of curcumin and 3 acetyl-11-keto-β-boswellic acid (AKBA) on modulation of specific cancer-related miRNAs in colorectal cancer cells and validated their protective effects in vivo using a xenograft mouse model. Both curcumin and AKBA inhibited cellular proliferation, induced apoptosis and cell-cycle arrest in colorectal cancer cell lines, and these effects were significantly enhanced with combined treatment. Gene-expression arrays revealed that curcumin and AKBA regulated distinct cancer signaling pathways, including key cell-cycle regulatory genes. Combined bioinformatics and in silico analysis identified apoptosis, proliferation, and cell-cycle regulatory signaling pathways as key modulators of curcumin and AKBA-induced anticancer effects. We discovered that curcumin and AKBA induced upregulation of tumor-suppressive miR-34a and downregulation of miR-27a in colorectal cancer cells. Furthermore, we demonstrated in a mouse xenograft model that both curcumin and AKBA treatments suppressed tumor growth, which corresponded with alterations in the expression of miR-34a and miR-27a, consistent with our in vitro findings. Herein, we provide novel mechanistic evidence for the chemopreventive effects of curcumin and AKBA through regulation of specific miRNAs in colorectal cancer.

Inversion of exons 1-7 of the MSH2 gene is a frequent cause of unexplained Lynch syndrome in one local population

Germline mutations in DNA mismatch repair (MMR) genes, such as MSH2, cause Lynch syndrome, an autosomal dominant predisposition to colorectal as well as other cancers. Our research clinic focuses on hereditary colorectal cancer, and over the past 9 years we have identified germline mutations in DNA MMR genes in 101 patients using commercial genetic reference laboratories. We also collected samples from twelve patients with absent MSH2 protein expression and microsatellite instability in tumor tissue, with a family history suggestive of Lynch syndrome, but negative germline test results. The most likely explanation for this set of results is that the germline testing did not detect true germline mutations in these patients. Two of our patients with failed commercial testing were later found to have deletions in the 3' region of EPCAM, the gene just upstream of MSH2, but no explanation could be found for inactivation of MSH2 in the other ten patients. We used allelic dropout in long PCR to look for potential regions of rearrangement in the MSH2 gene. This method detected a potential rearrangement breakpoint in the same region of MSH2 where one breakpoint of a 10 Mb inversion was reported previously. We tested these ten patients for this inversion. Six of 10 patients had the inversion, indicating the importance of including testing for this inversion in patients suspected of having MSH2-type Lynch syndrome in our population. Additionally, this method could be further developed to look for inversions in other genes where current methods of testing fail to find a causative mutation.

Identification of a metastasis-specific MicroRNA signature in human colorectal cancer

BACKGROUND

Distant metastasis is the major cause of mortality in colorectal cancer (CRC). We performed a systemic, comprehensive discovery for expression patterns of metastasis-specific microRNAs (miRNAs) by directly comparing primary CRCs (pCRCs) and matched liver metastases (LMs) and evaluated the feasibility of their clinical application as metastasis-specific biomarkers.

METHODS

CRC metastasis-specific miRNA profiles were generated by analyzing nine pairs of pCRC and LM tissues, followed by quantitative validation in an independent cohort of 58 pairs of matched pCRC and LM tissues. We evaluated associations between miRNA expression and patient survival and ability to predict metastasis in another 84 patients with CRC. Subsequently, associations were quantitatively validated in 175 CRC tissues and 169 serum samples. Kaplan-Meier, Cox regression, and logistic regression analyses were used. All statistical tests were two-sided.

RESULTS

Twenty-three miRNAs were identified that were differentially expressed between pCRC and LM (P < .001; FDR < .5). Four miRNAs downregulated in LM (let-7i, miR-10b, miR-221, and miR-320a) and one upregulated miR (miR-885-5p) were quantitatively validated in pCRC (P < .0001). Low let-7i expression in pCRC tissue predicted worsened prognosis (hazard ratio [HR] = 5.0, 95% confidence interval [CI] = 1.0 to 24.4, P = .0479) as well as distant metastasis (odds ratio [OR] = 5.5, 95% CI = 1.1 to 26.8, P = .0334). High miR-10b expression in pCRC tissue independently predicted distant metastasis (OR = 4.9, 95% CI = 1.2 to 19.7, P = .0248). High serum miR-885-5p expression independently predicted prognosis (HR = 2.9, 95% CI = 1.1 to 7.5, P = .0323), LN metastasis (OR = 3.0, 95% CI = 1.3 to 7.2, P = .0116), and distant metastasis (OR = 3.1, 95% CI = 1.0 to 10.0, P = .0456), whereas tissue miR-885-5p expression did not. Expression patterns of miRNAs were confirmed by in situ hybridization.

CONCLUSIONS

We discovered a metastasis-specific miRNA signature in pCRCs and discovered novel tissue- and serum-based CRC metastasis-specific miRNA biomarkers through intensive validation. These unique miRNAs may be clinically applicable to predict prognosis and distant metastasis in CRC.

Curcumin mediates chemosensitization to 5-fluorouracil through miRNA-induced suppression of epithelial-to-mesenchymal transition in chemoresistant colorectal cancer

Resistance to cytotoxic chemotherapy is a major cause of mortality in colorectal cancer (CRC) patients. Chemoresistance has been linked primarily to a subset of cancer cells undergoing epithelial-mesenchymal transition (EMT). Curcumin, a botanical with antitumorigenic properties, has been shown to enhance sensitivity of cancer cells to chemotherapeutic drugs, but the molecular mechanisms underlying this phenomenon remain unclear. Effects of curcumin and 5-fluorouracil (5FU) individually, and in combination, were examined in parental and 5FU resistant (5FUR) cell lines. We performed a series of growth proliferation and apoptosis assays in 2D and 3D cell cultures. Furthermore, we identified and analyzed the expression pattern of a subset of putative EMT-suppressive microRNAs (miRNAs) and their downstream target genes regulated by curcumin. Chemosensitizing effects of curcumin were validated in a xenograft mouse model. Combined treatment with curcumin and 5FU enhanced cellular apoptosis and inhibited proliferation in both parental and 5FUR cells, whereas 5FU alone was ineffective in 5FUR cells. A group of EMT-suppressive miRNAs were upregulated by curcumin treatment in 5FUR cells. Curcumin suppressed EMT in 5FUR cells by downregulating BMI1, SUZ12 and EZH2 transcripts, key mediators of cancer stemness-related polycomb repressive complex subunits. Using a xenograft and mathematical models, we further demonstrated that curcumin sensitized 5FU to suppress tumor growth. We provide novel mechanistic evidence for curcumin-mediated sensitization to 5FU-related chemoresistance through suppression of EMT in 5FUR cells via upregulation of EMT-suppressive miRNAs. This study highlights the potential therapeutic usefulness of curcumin as an adjunct in patients with chemoresistant advanced CRC.

Preoperative serum microRNA-203 as a novel prognostic and metastasis-predictive biomarker in patients with colorectal cancer

564

Background: Distant metastasis is the major causes of death in colorectal cancer (CRC) patients. Epithelial-mesenchymal transition (EMT) is a key process that converts polarized immotile epithelial cells into motile, invasive mesenchymal cells, enabling cancer cells to gain stem cell characteristics and an aggressive malignant phenotype such as metastasis. Mir-203 has been shown to directly suppress EMT activators such as ZEB2 and SNAI1/2. However, in spite of the key functional role of miR-203 in cancer metastasis, no previous studies have investigated the clinical significance of miR-203 in patients with CRC. Methods: To examine whether CRCs secret miR-203 in vitro and vivo,we first determined extracellular miR-203 levels in CRC cell culture media. Then, we quantified miR-203 levels in serum from mice with or without metastasis. Next, we investigated miR-203 expression in 58 pairs of primary CRC (pCRC) and corresponding matching liver metastasis (LM), as well as 186 serum and 154 matched tissue specimens from CRC patients. Results: HT-29 cells released miR-203 into culture media, which was dependent on cell number and duration of culture. In addition, high serum miR-203 levels were observed in mice with liver metastasis compared to control animals (p=0.0181). Mir-203 expression was significantly upregulated in LM compared to matching pCRC tissues (p=0.0002). Serum miR-203 was significantly upregulated in a tumor stage-dependent manner (p=0.0070), and high miR-203 expression was associated with poor survival in CRC patients (p<0.0001). In contrast to serum, no significant association between miR-203 expression in CRC tissues and clinicopathological findings was recognized. High serum miR-203 expression was an independent risk factor for poor prognosis (HR=2.1) as well as metastasis to lymph nodes (OR=2.5), liver (OR=6.2), peritoneum (OR=7.2), and distant organs (OR=4.4), respectively. Conclusions: High levels of serum miR-203, which may be derived from several metastatic sites, are associated with poor survival and metastasis, suggesting it is a promising non-invasive prognostic and metastasis-predictive biomarker in patients with CRC.

Technical factors involved in the measurement of circulating microRNA biomarkers for the detection of colorectal neoplasia

Background

Circulating miRNAs are emerging as promising blood-based biomarkers for colorectal and other human cancers; however, technical factors that confound the development of these assays remain poorly understood and present a clinical challenge. The aim of this study was to systematically evaluate the effects of factors that may interfere with the accurate measurement of circulating miRNAs for clinical purposes.

Methods

Blood samples from 53 subjects, including routinely drawn serum samples, matched plasma from 30 subjects, and matched serum samples drawn before and after bowel preparation for colonoscopy from 29 subjects were collected. Additionally, 38 serum specimens stored in the clinical laboratory for seven days were used to test the stability of miRNAs. Hemolysis controls with serial dilutions of hemoglobin were prepared. RNA was extracted from serum, plasma or hemolyzed controls with spiked-in cel-miR-39, and levels of miR-21, miR-29a, miR-125b and miR-16 were examined by real-time RT-PCR. Hemolysis was measured by spectrophotometry.

Results

The expression levels of miR-16 and the degree of hemolysis were significantly higher in plasma than in serum (P<0.0001). Measured miR-21, miR-29a, miR-125b and miR-16 expression increased with hemoglobin levels in hemolyzed controls. The degree of hemolysis in serum samples correlated significantly with the levels of miR-21 (P<0.0001), miR-29a (P = 0.0002), miR-125b (P<0.0001) and miR-16 (P<0.0001). All four miRNAs showed significantly lower levels in sera that had been stored at 4°C for seven days (P<0.0001). Levels of miR-21 (P<0.0001), miR-29a (P<0.0001) and miR-16 (P = 0.0003), and the degree of hemolysis (P = 0.0002) were significantly higher in sera drawn after vs. before bowel preparation.

Conclusions

The measured levels of miRNAs in serum and plasma from same patients varied in the presence of hemolysis, and since hemolysis and other factors affected miRNA expression, it is important to consider these confounders while developing miRNA-based diagnostic assays.

Selenomethionine induces p53 mediated cell cycle arrest and apoptosis in human colon cancer cells

While there is an increasing interest in selenium chemoprevention against human colon polyp recurrence and other cancers, the mechanism(s) by which these agents inhibit carcinogenesis are uncertain. Some of the proposed mechanisms include the inhibition of cytosine methyltransferases, carcinogen bioactivation, and inhibition of cyclooxygenase (COX). More recently, it has been suggested that selenium may exert growth inhibitory effects by activating p53. However, the molecular mechanisms of action of selenomethionine, an organoselenium compound present in selenized yeast and currently being investigated in human clinical trials for colon polyp prevention, are unclear. In the present study we tested the hypothesis that selenomethionine might affect colon cancer cell growth by p53 mediated apoptosis and/or cell cycle regulation. Four human colon cancer cell lines including HCT116 and RKO (wild type p53), HCT116-p53KO (isogenic control of HCT116 cells with p53 knocked out) and Caco-2 (mutant p53) were treated with 0-100 microM of selenomethionine for 24, 48 and 72 h. Cell viability rates were determined by the MTT assay. Cell cycle analysis was performed by flow cytometry and apoptosis measured by Annexin V-Cy5 staining. Expression of p53 protein was determined by Western blotting and immunofluorescence assays. All cell lines showed concentration and time dependent growth inhibition with selenomethionine, although HCT116 and RKO cells were the most sensitive to such treatments. Interestingly, although HCT116 and HCT116-p53KO are isogenic cell lines, selenomethionine caused a G2/M cell cycle arrest in HCT116 and RKO cells, but not in HCT116-p53KO cells. Similarly, both HCT116 and RKO demonstrated a significant increase in apoptosis (100-170%; p < 0.01) with 50-100 microM selenomethionine. Cell cycle arrest and apoptosis observed in HCT116 and RKO cell lines were accompanied by a marked increase in p53 protein expression following selenium treatment. These results clearly suggest that selenomethionine exerts p53 dependent growth inhibitory effects in colon cancer cells by inducing G2/M cell cycle arrest as well as apoptosis.

Metastasis-associated long non-coding RNA drives gastric cancer development and promotes peritoneal metastasis

The prognosis of gastric cancer (GC) patients with peritoneal dissemination remains poor, and a better understanding of the underlying mechanisms is critical for the development of new treatments that will improve survival in these patients. This study aimed to clarify the clinical and biological role of two key metastasis-associated long non-coding RNAs (lncRNAs) in GC. We analyzed the expression levels of two lncRNAs-Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1) and HOX-Antisense Intergenic RNA (HOTAIR)-by real-time reverse transcription PCR in 300 gastric tissues (150 GC and 150 adjacent normal mucosa), and in seven GC cell lines. Functional characterization for the role of HOTAIR in GC was performed by small interfering RNA (siRNA) knockdown, followed by series of in-vitro and in-vivo experiments. Expression of both lncRNAs was significantly higher in cancerous tissues than in corresponding normal mucosa, and higher expression of these lncRNAs significantly correlated with peritoneal metastasis in GC patients. In addition, elevated HOTAIR expression emerged both as an independent prognostic and risk factor for peritoneal dissemination. SiRNA knockdown of HOTAIR in GC cells significantly inhibited cell proliferation, migration and invasion, but concurrently enhanced the anoikis rate in transfected cells. In an in vivo assay, HOTAIR siRNA-transfected MKN45 cells injected into nude mice inhibited the growth of xenograft tumors and peritoneal metastasis compared with controls. Our data provide novel evidence for the biological and clinical significance of HOTAIR expression as a potential biomarker for identifying patients with peritoneal metastasis, and as a novel therapeutic target in patients with gastric neoplasia.