Abstract 3738: IL-24 modulates the high mobility group (HMG) A1/miR222 /AKT signaling in lung cancer cells
Authors: Panneerselvam Janani , Srivastava Akhil , Muralidharan Ranganayaki , Wang Qi , Zheng Wei , Zhao Lichao , Chen Allshine , Zhao Yan , Munshi Anupama , Ramesh Rajagopal 
Published: July 2016

Background: High mobility group A1 (HMGA1), a member of the non-histone chromosomal proteins and commonly referred to as architectural transcription factor, regulates transcription of various genes involved in cell growth and survival. Overexpression of HMGA1 has been shown to be associated with tumor progression and metastasis in several cancers, including human lung cancer. A recent study demonstrated that HMGA1 activates AKT function by reducing the activity of the protein phosphatase, phosphatase 2A subunitB (PPPR2A) via the oncogenic micro (mi) RNA-222. We demonstrated that interleukin (IL)-24, a novel tumor suppressor/cytokine, inhibited AKT in lung cancer cells. However, the molecular mechanism of AKT inhibition by IL-24 remains elusive.

Aim: To determine the molecular mechanism of IL-24-mediated AKT inhibition involved the HMGA1/miR-222 axis.

Methods: Human H1299 lung tumor cell line was stably transfected with a tetracycline-inducible plasmid vector carrying the IL-24. After the induced expression of IL-24 protein, expression levels of HMGA1 and its downstream molecular mechanisms were analyzed at the RNA and protein levels in lung cancer cell lines. The inhibitory effect of IL-24 on HMG A1/miR222 /AKT axis in the lung cancer cells is determined by RT-qPCR, western blot, reporter assay, and immunocytochemistry. Mechanistic approaches on overexpression and knockdown of HMGA1 and or miR-222 were utilized and the consequences of its inhibition/overexpression were analyzed on HMGA1/miR222 /AKT signaling axis and in vitro migration and invasion.

Results: Upon induction of IL-24 expression in the H1299 lung tumor cells, we observed a marked reduction in HMGA1protein and mRNA levels. Using a mechanistic approach, we found that IL-24 reduced miR-222-3p and -5p levels, as determined by qRT-PCR. Associated with HMGA1 and miR-222 inhibition was a marked increase in PPP2R2A, with a concomitant decrease in phosphorylated AKTT308/S473 expression. SiRNA-mediated knockdown of HMGA1in combination with IL-24 significantly reduced AKT T308/S473 protein expression and greatly reduced cell migration and invasion compared with individual treatments. Further combination of IL-24 and a miR-222-3p inhibitor significantly increased PPP2R2A expression.

Conclusion: Our results demonstrate for the first time that IL-24 inhibits AKT via regulating the HMGA1/miR-222 signaling node in human lung cancer cells and acts as an effective tumor suppressor. HMGA1 should present a novel target for the effective treatment of lung cancer.

Citation Format: Janani Panneerselvam, Akhil Srivastava, Ranganayaki Muralidharan, Qi Wang, Wei Zheng, Lichao Zhao, Allshine Chen, Yan Zhao, Anupama Munshi, Rajagopal Ramesh. IL-24 modulates the high mobility group (HMG) A1/miR222 /AKT signaling in lung cancer cells. [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 3738.