Differential expression of colon cancer associated transcript1 (CCAT1) along the colonic adenoma-carcinoma sequence

BACKGROUND

The transition from normal epithelium to adenoma and, to invasive carcinoma in the human colon is associated with acquired molecular events taking 5-10 years for malignant transformation. We discovered CCAT1, a non-coding RNA over-expressed in colon cancer (CC), but not in normal tissues, thereby making it a potential disease-specific biomarker. We aimed to define and validate CCAT1 as a CC-specific biomarker, and to study CCAT1 expression across the adenoma-carcinoma sequence of CC tumorigenesis.

METHODS

Tissue samples were obtained from patients undergoing resection for colonic adenoma(s) or carcinoma. Normal colonic tissue (n = 10), adenomatous polyps (n = 18), primary tumor tissue (n = 22), normal mucosa adjacent to primary tumor (n = 16), and lymph node(s) (n = 20), liver (n = 8), and peritoneal metastases (n = 19) were studied. RNA was extracted from all tissue samples, and CCAT1 expression was analyzed using quantitative real time-PCR (qRT-PCR) with confirmatory in-situ hybridization (ISH).

RESULTS

Borderline expression of CCAT1 was identified in normal tissue obtained from patients with benign conditions [mean Relative Quantity (RQ) = 5.9]. Significant relative CCAT1 up-regulation was observed in adenomatous polyps (RQ = 178.6 ± 157.0; p = 0.0012); primary tumor tissue (RQ = 64.9 ± 56.9; p = 0.0048); normal mucosa adjacent to primary tumor (RQ = 17.7 ± 21.5; p = 0.09); lymph node, liver and peritoneal metastases (RQ = 11,414.5 ± 12,672.9; 119.2 ± 138.9; 816.3 ± 2,736.1; p = 0.0001, respectively). qRT-PCR results were confirmed by ISH, demonstrating significant correlation between CCAT1 up-regulation measured using these two methods.

CONCLUSION

CCAT1 is up-regulated across the colon adenoma-carcinoma sequence. This up-regulation is evident in pre-malignant conditions and through all disease stages, including advanced metastatic disease suggesting a role in both tumorigenesis and the metastatic process.

Colon cancer associated transcript-1: a novel RNA expressed in malignant and pre-malignant human tissues

Early detection of colorectal cancer (CRC) is currently based on fecal occult blood testing (FOBT) and colonoscopy, both which can significantly reduce CRC-related mortality. However, FOBT has low-sensitivity and specificity, whereas colonoscopy is labor- and cost-intensive. Therefore, the discovery of novel biomarkers that can be used for improved CRC screening, diagnosis, staging and as targets for novel therapies is of utmost importance. To identify novel CRC biomarkers we utilized representational difference analysis (RDA) and characterized a colon cancer associated transcript (CCAT1), demonstrating consistently strong expression in adenocarcinoma of the colon, while being largely undetectable in normal human tissues (p < 000.1). CCAT1 levels in CRC are on average 235-fold higher than those found in normal mucosa. Importantly, CCAT1 is strongly expressed in tissues representing the early phase of tumorigenesis: in adenomatous polyps and in tumor-proximal colonic epithelium, as well as in later stages of the disease (liver metastasis, for example). In CRC-associated lymph nodes, CCAT1 overexpression is detectable in all H&E positive, and 40.0% of H&E and immunohistochemistry negative lymph nodes, suggesting very high sensitivity. CCAT1 is also overexpressed in 40.0% of peripheral blood samples of patients with CRC but not in healthy controls. CCAT1 is therefore a highly specific and readily detectable marker for CRC and tumor-associated tissues.

Abstract 1172: The impact of siRNA targeting Colon Cancer Associated Transcript 1 (CCAT-1) on proliferation of HT-29 cells

Introduction: Colon cancer Associated Transcript-1 (CCAT-1) is a non-coding RNA transcript highly expressed in colorectal cancer (CRC) but not in normal colonic tissue. The role of CCAT-1 in tumorigenesis is yet to be defined. Small interfering RNAs (siRNA) are a group of sequence-specific posttranscriptional gene silencing molecules. Recent advances in the design and delivery of targeting siRNA molecules allows efficient and highly specific gene silencing in mammalian systems. The most common application of siRNA gene-silencing in oncology is to identify loss-of-function phenotypes in genes that will result in decreased proliferation or death of cancer cells.

Aim: To study the role of colon cancer associated transcript 1 (CCAT-1) in proliferation of human colon cancer cells using RNA interference.

Methods: Small interfering RNAs (siRNA) targeting CCAT-1 were transfected into HT-29 colon cancer cells. At day one, 80×105 HT-29 cells per well were plated and suspended in RPMi 1640 medium. At day two, 50 pmol CCAT-1 siRNA and 0.5 µl lipofectamine 2000 were added to each well. CCAT-1 expression was studied by real-time PCR in order to evaluate gene silencing. Cell proliferation was studied by MTT incorporation assay. Twenty four hrs after transfection, 50 µl of MTT were added to the cells media and incubated for 4 h at 37° C. The purple Formazan product, converted MTT, was dissolved by the addition of 150µl/well DMSO and OD readings were obtained at 550 nm.

Results:By examining AV average OD readings at 550 nm, untreated HT-29 cells (10 wells), cells treated with lipofectamine 2000 (10 wells) and cells silenced by siRNA of CCAT-1 (10 wells) showed a significant decrease in proliferation: 2.4±0.64, 1.54±0.63, 0.8±0.14 respectively (p=0.002). Furthermore, comparing AV OD readings between 24 and 48 h in the silenced cells, showed a decrease of 38% in proliferation. This was compared to untransfected cells and cells treated with lipofectamine 2000 which showed an increase of 39% and 22% respectively. Twenty four hrs after transfection, real time PCR results showed a reduction in CCAT-1 RNA levels of 70% compared to controls and 48 hrs after transfection, CCAT-1 RNA levels were reduced to 55% of baseline.

Conclusions: Our results may support a role for CCAT-1 in the regulation of colon cancer cell proliferation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1172. doi:10.1158/1538-7445.AM2011-1172

Development of a microRNA-based molecular assay for the detection of papillary thyroid carcinoma in aspiration biopsy samples

BACKGROUND

Although thyroid nodules are common and diagnosed in over 5% of the adult population, only 5% harbor malignancy. Patients with clinically suspicious thyroid nodules need to undergo fine-needle aspiration biopsy (FNAB). The main limitation of FNAB remains indeterminate cytopathology. Only 20%-30% of the indeterminate nodules harbor malignancy, and therefore up to 80% of patients undergo unnecessary thyroidectomy. The aim of this study was to identify and validate a panel of microRNAs (miRNAs) that could serve as a platform for an FNAB-based diagnostic for thyroid neoplasms.

METHODS

The study population included 27 consecutive patients undergoing total thyroidectomy for FNAB-based papillary thyroid cancer (n = 20) and benign disorders (n = 7). Aspiration biopsy was performed from the index lesion and from the opposite lobe normal tissue in all study patients at the time of operation. RNA was extracted from all aspiration biopsy samples. Quantitative polymerase chain reaction on a panel of previously selected miRNAs was performed. Polymerase chain reaction results were compared with final histopathology. miRNA from tumor tissues was amplified using the highest value of each miRNA expression in normal tissue as a threshold for malignancy detection.

RESULTS

Diagnostic characteristics were most favorable for mir-221 in differentiating benign from malignant thyroid pathology. mir-221 was overexpressed in 19 patients (p < 0.0001) with a sensitive yield of 95%. Specificity, negative and positive predictive value, and accuracy of the miRNA panel were 100%, 96%, 100%, and 98%, respectively.

CONCLUSIONS

miRNA quantification for differential diagnosis of thyroid neoplasms within aspiration biopsy samples is feasible and may improve the accuracy of FNAB cytology.

Abstract 3016: The value of microRNAs in the detection and staging of colorectal cancer

Introduction: MicroRNAs (miRNAs) are a large class of single strand RNA molecules consistent of 18-25 nucleotides, involved in post transcriptional gene silencing. miRNAs show tissue-specific expression and play an important role in carcinogenesis.

The aim of the present study was: A. to identify colorectal cancer (CRC)-specific miRNAs. B. To study the potential value of CRC-specific miRNAs in CRC detection and staging.

Methods: This study was approved by the Institutional Review Board (IRB). RNA was extracted from paired samples of normal and tumor tissue of CRC patients (n=10). miRNA expression was tested using a commercially available array. Differential expression between normal and tumor tissues was identified in 30 human miRNAs and in additional 16 miRNAs identified from database mining. Differential expression was validated by quantitative (real-time) PCR in a larger cohort of samples (n=20). RNA was extracted from sentinel lymph nodes (SLN) of CRC patients. A calibration plot was generated using a CRC cell line (HT29) mixed with peripheral blood lymphocytes (PBL) of healthy donors in a range of concentrations.

Results: After validation, only 8 miRNAs were found to be overexpressed in CRC.

The detection threshold for all 8 miRNAs measured by the calibration plot was 1:1000 (one HT-29 cell in 1000 PBMCs). The expression of the 8 miRNAs was then tested in SLNs (n=86). Fourteen lymph nodes (16.3%) were positive by standard pathological examination (H&E staining) and 25/86 (29.1%) were positive by miRNA expression analysis (p&lt;0.01). miRNA expression was detected in all sera from CRC patients (n=3) and in none of the sera obtained from healthy individuals (n=5, p&lt;0.0001).

Conclusions: A panel of 8 miRNAs was found to be overexpressed in CRC patients. Occult residual disease was indentified in lymph nodes and serum of CRC patients using this miRNA panel.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3016.