PI3K-Akt and Ras-Raf-MAPK signaling in colorectal cancer – Comparison of activity in primary tumor tissues and primary tumour – Derived human colorectal cancer cell lines
A. Wach, , K. Kałuzińska, P. Frączek
Chair of Medical Biochemistry, Estonia

Aim: The study aimed to compare the differences in activity of PI3K-Akt and Ras-Raf-MAPK pathways, and changes in the Ras-Raf-MAPK activity after PI3K-Akt silencing, between different cell lines and tissue samples from primary tumour sites of human CRC.

Introduction: Alterations in EGFR-related Ras-Raf-MAPK and PI3K-Akt pathways are involved in the pathogenesis of up to 55% and 15% colorectal cancers (CRC) respectively. The Ras-Raf-MAPK pathway mutations are assessed before introducing a standard anti-EGFR treatment, as they indicate lack of response. However, the autonomic activity of alternative PI3K-Akt pathway may also have an impact on the effectiveness of targeted therapy.

Methods: The study was carried out on three ATCC human CRC cell lines derived from primary tumours (COLO320, SW480 and HT29) and ten patient tissue samples. Cell lines were cultured according to the protocol. Genomic DNA and RNA were isolated, PCR and RT-PCR were performed. Restriction enzymes were applied. Primers for the following fragments of genome were used: KRAS (exons 2, 3, 4), NRAS (exons 2, 3, 4), and BRAF exon 15 for PCR; KRAS, NRAS, BRAF, PIK3CA for RT-PCR. Proteins were extracted, purified and Western Blot was conducted. siRNA for Akt and specific PI3K inhibitors were used to silence PI3K-Akt activity.

Results: The analyzed material presented variable profiles of pathways activity. Interestingly, high expression of Ras protein was positively correlated with Akt protein level. In case of low level of Ras, Raf protein was dominating whereas Akt expression was significantly decreased.

Conclusion: Ras and Akt can simultaneously present a high level of expression. Thus, as PI3K- Akt is an alternative pathway to Ras-Raf- MAPK for EGFR signaling and its autonomic activity may affect the efficacy of anticancer treatment, it has a potential to be taken into consideration while planning a treatment and developing new anticancer agents.1,2

D.M. Muzny,M.N. Bainbridge
Comprehensive molecular characterization of human colon and rectal cancer
Nature, 487 (2012), pp. 330-337
K. Khwanraj,S. Madlah
Comparative mRNA expression of eEF1A isoforms and a PI3K/Akt/mTOR pathway in a cellular model of parkinson's disease
Hindawi Publishing Corporation, (2016)pp. 11
Article ID 8716016

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