Downregulation of the PI3k/Akt pathway leads to decreased invasion of the human colon cancer cells

Abstract Introduction: The breakdown of the extracellular matrix (ECM) by proteinases is an essential step in cancer invasion and metastasis. Of the four known membrane type matrix metalloproteinases, MT1-MMP is most often overexpressed in cancers and is frequently detected in association with the activated form of MMP-2. We have shown that activation of the phosphotidylinositol-3 kinase (PI3K) pathway, acting through Akt/PKB, stimulates invasion of KM20 colon cancer cells. Therefore, the purpose of our study was to determine whether small interfering RNA (siRNA)-mediated PI3K inhibition decreased KM20 cell invasiveness through MT1-MMP expression Methods: siRNAs directed to the p85alpha (PI3K subunit), Akt1, Akt2 or scrambled sequences (control) were synthesized and transfected into KM20 cells. The gelatinolytic activity of MMP-2 was analyzed by gelatin zymography. Tumor cell invasion was measured using reconstituted basement membrane (Matrigel). RNA was extracted and analyzed by RNase protection assays using a multi-probe (hMMP-2; Pharmingen) to detect changes in gene expression. Results: siRNA-mediated PI3K/Akt inhibition blocked MT1-MMP induction and significantly decreased (∼90%) KM20 tumor invasion through Matrigel in response to IGF-I. Conversely, treatment with the MEK/ERK inhibitor, PD98059, had no effect on MT1-MMP induction or tumor invasion. Conclusions: Our results demonstrate that PI3K/Akt activation contributes to tumor cell invasion through induction of MTI-MMP; the selective targeting of the PI3K/Akt signaling pathway significally blocks the invasive potential of the aggressive KM20 cell line.