Targeting the AKT/mTOR pathway attenuates the metastatic potential of colorectal carcinoma circulating tumor cells in a murine xenotransplantation model

TL;DR

Blocking the AKT/mTOR pathway reduces the spread of colorectal cancer by targeting circulating tumor cells in a mouse model.

Contribution

Demonstrates that dual inhibition of AKT and mTOR effectively targets CTCs and reveals unique roles of AKT isoforms in tumor progression.

Findings

Dual AKT/mTOR inhibition with MK2206 and RAD001 reduces tumor burden in a mouse model of colon cancer.

AKT1 and AKT2 knockdowns each reduce CTC proliferation and regulate distinct sets of proteins and phospho-proteins.

AKT1/AKT2 double knockdown disrupts cell cycle and stem cell processes, highlighting non-redundant roles of AKT isoforms.

Abstract

Circulating tumor cells (CTCs) play an important role in metastasis formation. Aberrant signaling of oncogenic pathways (e.g., PI3K/AKT/mTOR pathway) drives tumor progression. In this work, the susceptibility of the colon cancer CTC‐derived cell line CTC‐MCC‐41 to AKT and mammalian target of rapamycin (mTOR) inhibitors was evaluated. Additionally, the functional role of the expressed AKT isoforms was characterized in this cell line. The efficacy of the AKT inhibitor MK2206, the mTOR inhibitor RAD001, and the combination was examined in CTC‐MCC‐41 cells in a murine intracardiac xenotransplantation model. Furthermore, stable isoform‐specific AKT1 or AKT2 knockdowns (KDs) as well as AKT1/AKT2 double‐KD cells were generated. Differentially regulated proteins and phospho‐peptides were identified using liquid chromatography coupled mass spectrometry (LC–MS). CTC‐MCC‐41 cells showed a high susceptibility for dual targeting of AKT and mTOR in vivo, indicating that selective eradication of CTCs by AKT/mTOR inhibitors may be considered a new treatment option in cancer. KD of AKT1 or AKT2 significantly reduced the proliferation of CTC‐MCC‐41 cells. AKT KDs share commonly regulated proteins and phospho‐proteins, but also regulate a large number uniquely. AKT1/AKT2 double‐KD cells show a strongly dysregulated replication machinery, as well as a decrease in cell cycle activity and stem‐cell‐associated processes, underlining the non‐redundant role of AKT isoforms.

Dual targeting of AKT and mTOR using MK2206 and RAD001 reduces tumor burden in an intracardiac colon cancer circulating tumor cell xenotransplantation model. Analysis of AKT isoform‐specific knockdowns in CTC‐MCC‐41 reveals differentially regulated proteins and phospho‐proteins by liquid chromatography coupled mass spectrometry.

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