Adaptation Of Colon Cancer Cells To The Brain Microenvironment: The Role Of IRS2

Introduction: Development of brain metastases (BMs) requires adaptation of cancer cells to the hostile brain environment (BE). BMs from colorectal cancer (CRC) are the fourths leading cause of BMs. Yet, mechanisms mediating the formation of CRC BMs are currently unknown. A possible candidate is insulin receptor substrate-2 (IRS-2), a cytoplasmic molecule mediating insulin and IGF-1 effects by acting as an adaptor between their receptors and downstream effectors.

We aimed to explore genomic drivers enabling tropism and adaptation of CRC cells to the BE and decipher mechanisms enabling the process.

Material and method: Analysis of FoundationOne database including 115 CRC BMs and 2935 CRC liver metastases (LMs). CRC cell line used was HCT-116. Proliferation was assessed using methylene-blue; migration using transwell and wound-healing assays. Three-dimensional model that recapitulates the BE was generated using InSphero assay. Conditioned media (CM) was prepared from brain and activated-human astrocytes (aHA). IRS2 expression was studied using IHC, qRT-PCR, and western-blot.

Results and discussion: Increased prevalence of IRS2 gene amplification was observed in 13% of BMs compared to 3% in LMs (p<0.0001). Furthermore, IHC of human clinical samples showed increased expression of IRS2 in BMs compared to LMs. Mimicking BE (hypoxia and brain or aHA CM) increased IRS2 expression in CRC cells. IRS2-overexpressed CRC cells had increased proliferation, migration and colony formation capacity. Finally, IRS2-overexpressed HCT-116 three-dimensional spheroids survived better in aHA-CM and had enhanced proliferation in co-culture with HA.>

Conclusion: These data indicate, for the first time, a unique genomic profile of CRC BMs and implies IRS2 role in promoting BMs. Understanding the mechanisms enabling CRC cells to colonize and grow in the brain may help to reveal novel therapeutic targets to inhibit development of BMs.