Two antisense RNAs-AFAP1-AS1 and MLK7-AS1-promote colorectal cancer progression by sponging miR-149-5p and miR-485-5p

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths. Antisense RNAs (asRNAs) are closely associated with cancer malignancy. This study aimed to identify the action mechanism of asRNAs in controlling CRC malignancy. Analysis of the RNA sequencing data revealed that AFAP1-AS1 and MLK7-AS1 were upregulated in CRC patients and cell lines. High levels of both asRNAs were associated with poor prognosis in patients with CRC. Both in vitro and in vivo experiments revealed that the knockdown of the two asRNAs decreased the proliferative and metastatic abilities of CRC cells. Mechanistically, AFAP1-AS1 and MLK7-AS1 decreased the levels of miR-149-5p and miR-485-5p by functioning as ceRNAs. Overexpression of miRNAs by introducing miRNA mimics suppressed the expression of SHMT2 and IGFBP5 by directly binding to the 3' UTR of their mRNA. Knockdown of both asRNAs decreased the expression of SHMT2 and IGFBP5, which was reversed by inhibition of both miRNAs by miRNA inhibitors. In vivo pharmacological targeting of both asRNAs by small interfering RNA-loaded nanoparticles showed that knockdown of asRNAs significantly reduced tumor growth and metastasis. Our findings demonstrate that AFAP1-AS1 and MLK7-AS1 promote CRC progression by sponging the tumor-suppressing miRNAs miR-149-5p and miR-485-5p, thus upregulating SHMT2 and IGFBP5.

Expression of SLC22A18 regulates oxaliplatin resistance by modulating the ERK pathway in colorectal cancer

Although oxaliplatin-based chemotherapy is the current standard adjuvant therapy for colorectal cancer (CRC), the molecular mechanisms underlying oxaliplatin resistance remain unclear. Here, we examined the molecular mechanisms underlying SLC22A18-associated oxaliplatin resistance and strategies for overcoming oxaliplatin resistance. We evaluated the association between SLC22A18 and prognosis in 337 patients with CRC and its functional significance and studied the mechanisms through which SLC22A18 affects oxaliplatin resistance development in CRC cells, using CRC cell lines and patient-derived cells (PDCs). SLC22A18 downregulation was positively correlated with worse survival in patients with CRC. Low SLC22A18-expressing cells showed relatively lower sensitivity to oxaliplatin than high SLC22A18-expressing cells. In addition, ERK activation was found to be involved in the mechanisms underlying SLC22A18-related oxaliplatin resistance. To confirm ERK pathway dependence, we used an ERK inhibitor and found that combined treatment with oxaliplatin and the ERK inhibitor overcame oxaliplatin resistance in the low SLC22A18-expressing cells. Ex vivo approaches using PDC confirmed the correlation between SLC22A18 expression and oxaliplatin resistance. Results of the in vivo study showed that SLC22A18 expression regulated oxaliplatin efficacy, and that combined treatment with an ERK inhibitor could be a useful therapeutic strategy when SLC22A18 is downregulated. Together, our findings indicate that SLC22A18 could serve as a biomarker for the prediction of oxaliplatin resistance. In cases of oxaliplatin resistance due to low SLC22A18 expression, resistance can be overcome by combined treatment with an ERK inhibitor.

Establishment of patient-derived organotypic tumor spheroid models for tumor microenvironment modeling

Patient‐derived cancer models that reconstitute the characteristics of the tumor microenvironment may facilitate efforts in precision immune‐oncology and the discovery of effective anticancer therapies. Organoids that have recently emerged as robust preclinical models typically contain tumor epithelial cells and lack the native tumor immune microenvironment. A patient‐derived organotypic tumor spheroid (PDOTS) is a novel and innovative ex vivo system that retains key features of the native tumor immune microenvironment. Here, we established and characterized a series of colorectal cancer PDOTS models for use as a preclinical platform for testing effective immunotherapy and its combinations with other drugs. Partially dissociated (> 100 μm in diameter) tumor tissues were embedded in Matrigel‐containing organoid media and subsequently formed into organoid structures within 3 to 7 days of culture. The success rate of growing PDOTS from fresh tissues was ~86%. Morphological analysis showed that the PDOTSs varied in size and structure. Immunofluorescence and flow cytometry analysis revealed that the PDOTSs retained autologous tumor‐infiltrating lymphoid cells and tumor‐infiltrating lymphoid cells were continually decreased through serial passages. Notably, PDOTSs from tumors from a high‐level microsatellite instability‐harboring patient were sensitive to anti‐PD‐1 or anti‐PD‐L1 antibodies. Our results demonstrate that the PDOTS model in which the tumor immune microenvironment is preserved may represent an advantageous ex vivo system to develop effective immune therapeutics.

Correction: MicroRNA-17-5p regulates EMT by targeting vimentin in colorectal cancer

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

MicroRNA-17-5p regulates EMT by targeting vimentin in colorectal cancer

Background

Epithelial–mesenchymal transition (EMT) is the most common cause of death in colorectal cancer (CRC). In this study, we investigated the functional roles of miRNA-17-5p in EMT of CRC cells.

Methods

In order to determine if miRNA-17-5p regulated EMT, the precursors and inhibitors of miR-17-5p were transduced into four CRC cells. To evaluate the regulatory mechanism, we performed argonaute 2 (Ago2) immunoprecipitation (IP) and luciferase assay. In addition, we used an intra-splenic injection mouse model of BALB/c nude mice to investigate the metastatic potential of miRNA-17-5p in vivo.

Results

The miRNA-17-5p expression was lower in primary CRC tissues with metastasis than in primary CRC tissues without metastasis in our RNA sequencing data of patient tissue. Real-time quantitative PCR revealed that miRNA-17-5p was inversely correlated with that of vimentin in five CRC cell lines. Over-expression of miRNA-17-5p decreased vimentin expression and inhibited cell migration and invasion in both LoVo and HT29 cells. However, inhibition of miRNA-17-5p showed the opposite effect. Ago2 IP and luciferase assay revealed that miRNA-17-5p directly bound to the 3′UTR of VIM mRNA. Furthermore, miRNA-17-5p inhibited the metastasis of CRC into liver in vivo.

Conclusions

Our results demonstrated that miRNA-17-5p regulates vimentin expression, thereby regulating metastasis of CRC.

Efficient primary culture model of patient‑derived tumor cells from colorectal cancer using a Rho‑associated protein kinase inhibitor and feeder cells

In vitro culture of patient‑derived tumor cells offers many advantages in the development of novel therapies for colorectal cancer. Although various culture systems have been developed, the long‑term expansion of patient‑derived tumor cells remains challenging. The present results suggested that tumor cells isolated from colorectal cancer patient‑derived xenografts can be efficiently immortalized in conditioned medium from irradiated feeder cells containing Y‑27632, a rho‑associated coiled‑coil containing protein kinase (ROCK) inhibitor. Patient‑derived tumor cells proliferated rapidly, reaching 90‑95% confluence in ~6 days. Short tandem repeat analysis suggested that these tumor tissues and cultured cells presented 13 identical short tandem repeat loci, including Amelogenin, Penta E, Penta D, D2S1338 and D19S433. Their epithelial phenotype was confirmed by staining for epithelial cell adhesion molecule and cytokeratin 20, whereas vimentin was used as a mesenchymal marker. When cells were transferred to 3D cultures, they continued to proliferate, forming well‑defined tumor spheroids. Expression levels of human telomerase reverse transcriptase and C‑Myc mRNA were increased in cultured cells. Finally, immortalized cells were used for the screening of 65 anticancer drugs approved by the Food and Drug Administration, allowing the identification of gene‑drug associations. In the present study, primary culture models of colorectal cancer were efficiently established using a ROCK inhibitor and feeder cells, and this approach could be used for personalized treatment strategies for patients with colorectal cancer.

Abstract 492: Downregulation of microRNA-17-5p promotes EMT by targeting vimentin in colorectal cancer

Background: Colorectal cancer (CRC) is one of the most frequent forms of cancer worldwide. Cells with abnormal growth have the ability to invade or spread to other parts of the body (metastasis). Metastasis is the most common cause of death in CRC patients and activation of epithelial-mesenchymal transition (EMT) triggers metastasis. Thus, it is important to understand the mechanisms of EMT to increase the survival rate of CRC. MicroRNA-17 (miRNA-17) has been proven to be significantly higher in CRC tissues than normal tissues. However, there are few papers about the role of miRNA-17 in CRC metastasis. Therefore, in this study, we evaluated the mechanism underlying miRNA-17-5p related EMT in colon cancer cells.

Methods: Expression level of miRNA-17-5p as well as target mRNA were analyzed in HCT-15, HT29, LoVo, SW480 and COLO205 cell lines. In order to evaluate the correlation between miRNA-17-5p and EMT phenomenon, selected cell lines were transiently transfected either miRNA-17-5p mimic or miRNA-17-5p inhibitor and then phenotyping studies were conducted. Moreover, to find out the direct target of miRNA-17-5p, we performed AGO2 immunoprecipitation in each colon cancer cell lines.

Results: Real-time PCR revealed that miRNA-17-5p expression reversely correlated with vimentin expression in five colon cancer cell lines. Overexpression of miRNA-17-5p inhibited vimentin expression, cell migration and cell invasion in both LoVo and HT29 cells. On the other hand, inhibition of miRNA-17-5p promoted vimentin expression, cell migration and cell invasion in the same parallel cell lines. Through AGO2 immunoprecipitation analysis, we observed that miRNA-17-5p directly bind to vimentin 3'UTR to influence its stability and expression at the transcriptional level.

Conclusion: Our data demonstrated that down-regulated miRNA-17-5p promotes colon cancer cell migration and invasion by regulating vimentin expression. These findings propose that miRNA-17-5p may serve as a potential prognostic biomarker in colorectal cancer.

Citation Format: Tea Won Kim, Yeo Song Lee, Hye Kyung Hong, Su Jeong Song, Nak Hyeon Yun, Yong Beom Cho. Downregulation of microRNA-17-5p promotes EMT by targeting vimentin in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 492.