Abstract 3142: Stress regulated role of lncRNA Malat1 in colorectal cancer progression and metastasis
Authors: Doxtater Kyle , Zacheaus Chidi , Sekhri Radhika , Mishra Utkarsh K. , Stiles Zachary E. , Mishra Nitish , Guda Chittibabu , Zafar Nadeem , Amin Mahul , Shukla Pradeep , Yallapu Murali M. , Jaggi Meena , Chauhan Subhash C. , Tripathi Manish K. 
Published: September 2020

Background: Colorectal carcinoma (CRC) is the second leading cause of cancer related deaths in the United States. The five-year survival rate of patients diagnosed with distant stages declines to 14%, which is of concern when compared to 90% for localized-stage and 71% for regional stage disease. This necessitates the need for early diagnostic biomarkers, to minimize poor drug response/resistance, recurrence, metastasis and mortality. Disproportionate biochemical stressors increase the risk of developing CRC and its progression by influencing molecular drivers within the coding and noncoding parts of the genome. Thus, understanding the biological mechanism of these stress factors on the molecular drivers of this disease can provide pivotal information pertinent to CRC development and progression. Recently, our laboratory has identified a novel long noncoding RNA (lncRNA) namely, Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1), which is highly over-expressed in CRC and is involved in its pathogenesis and is regulated by transcription factor Nuclear Factor of Activated T cell 1 (NFATc1).

Methods: Archived human CRC tissues were stained using a recently standardized Z-probe technology. TCGA database of ~600 CRC patients was also analyzed using the bioinformatic approach. CRC cell lines were profiled for MALAT1 expression using RT-PCR. Lentiviral constructs were used to generate stable lncRNA MALAT1 expressing cell lines. CRISPR/Cas9 constructs were used to knockdown lncRNA MALAT1 and NFATc1. Mouse model was used to verify the stress induced expression of MALAT1 and NFATc1. ReCLP (Reversible Cross-Linked Precipitation) and iRAP (invitro RNA Antisense Proteomics) studies are in progress to identify the associated proteins and complexes.

Results: RNAScope analysis showed MALAT1 to be highly over-expressed in human CRC tissues. MALAT1 expression increased with stage and negatively correlated with the tumor size. TCGA database analysis confirmed our findings. Multiple NFATc1 binding site were identified by ChIPseq database. Overexpression of transcription factor NFATc1 upregulated lncRNA MALAT1 expression. CRISPR/Cas9 based knockdown of NFATc1 downregulated NFATC1 and lncRNA MALAT1, but vice versa was not true, indicating NFATc1 to be upstream of lncRNA MALAT1. Also, expression of MALAT1, NFATc1 and IL-6 were highly upregulated by biochemical stressor cortisol in mouse colonic tissues. Further studies are in progress for direct association of NFATc1 on MALAT1 promoter and mechanism by which the stress factor regulate NFATc1 expression and hence lncRNA MALAT1 expression.

Conclusion: This study helps to understand influence of biochemical stress factors on long noncoding RNA MALAT1 and transcription factor NFATc1 etiology. Early diagnosis of these molecular markers will help in designing novel preventive/therapeutic strategies to reduce CRC progression, metastasis and hence mortality.

Citation Format: Kyle Doxtater, Chidi Zacheaus, Radhika Sekhri, Utkarsh K. Mishra, Zachary E. Stiles, Nitish Mishra, Chittibabu Guda, Nadeem Zafar, Mahul Amin, Pradeep Shukla, Murali M. Yallapu, Meena Jaggi, Subhash C. Chauhan, Manish K. Tripathi. Stress regulated role of lncRNA Malat1 in colorectal cancer progression and metastasis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3142.