Targeting the PI3K-Akt-mTOR signaling pathway involved in vasculogenic mimicry promoted by cancer stem cells.

An accumulating body of evidence has led to the development of the cancer stem-cell (CSC) model which proposed that a subset of cells distinct from those that form the tumor mass regulated the tumor growth rate over a long period. Various types of therapy have been developed for cancer treatment. The major conventional therapies are chemotherapy, radiation therapy, and surgical excision. The other emerging therapies include targeted therapy using molecule-based agents. However, the resistance to chemotherapy and radiation therapy frequently occurs. This was most likely due to the dysregulated functioning of the multidrug efflux pumps and nucleotide repair systems resulting from the multiple interactions between the CSCs and the tumor microenvironment. Even though chimeric antigen receptor T-cell and immune checkpoint blockade therapies have succeeded remarkably for treating cancers, evidence suggested that CSCs promoted the development of resistance to these therapies and led to metastasis. The cells with stem cell-like features actively participate in vasculogenic mimicry in different types of cancer. In addition to melanoma, vasculogenic mimicry has been observed in various cancers. One of the major signaling pathways in CSCs is the phosphoinositide 3-kinase (PI3K)/Akt/PTEN pathway. PI3Ks are a family of enzymes that play a critical role in cellular growth, migration, differentiation, and vasculogenic mimicry. The PI3K-Akt pathway also plays a crucial role in epithelial-mesenchymal transition and the establishment of CSC-specific phenotypes through the PTEN/Akt mechanistic target of the rapamycin axis. Thus, targeting the PI3K pathway could be beneficial for cancer treatment through the elimination of CSCs, and such therapy might break niches which maintain the CSC, inhibit the metastasis, and suppress the recurrence of cancer.