Chronic exposure of VEGF inhibitors promotes the malignant phenotype of colorectal cancer cells

The malignant progression effects of regorafenib in human colon cancer cells

A number of anti-angiogenic drugs targeting vascular endothelial growth factor receptors (VEGF-R) have developed and enabled significant advances in cancer therapy including colorectal cancer. However, acquired resistance to the drugs occurs, leading to disease progression, such as invasion and metastasis. How tumors become the resistance and promote their malignancy remains fully uncertain. One of possible mechanisms for the resistance and the progression may be the direct effect of VEGF-R inhibitors on tumor cells expressing VEGF-R. We investigated here the direct effect of a VEGF-R-targeting agent, regorafenib, which is the first small molecule inhibitor of VEGF-Rs for the treatment of patients with colorectal cancer, on phenotype changes in colon cancer HCT116 cells. Treatment of cells with regorafenib for only 2 days activated cell migration and invasion, while vehicle-treated control cells showed less activity. Intriguingly, chronic exposure to regorafenib for 90 days dramatically increased migration and invasion activities and induced a resistance to hypoxia-induced apoptosis. These results suggest that loss of VEGF signaling in cancer cells may induce the acquired resistance to VEGF/VEGF-R targeting therapy by gaining two major malignant phenotypes, apoptosis resistance and activation of migration/invasion.

Second-line angiogenesis inhibition in metastatic colorectal cancer patients: Straightforward or overcrowded?

Although the number of therapeutic options targeting tumour angiogenesis is becoming increasingly relevant, the question of the optimal choice for second-line anti-angiogenic inhibition in combination with chemotherapy for metastatic colorectal cancer patients remains largely unanswered. In fact the lack of head to head comparison between consolidated options such as bevacizumab and new treatment alternatives such as aflibercept and ramucirumab makes the selection in the clinical practice challenging, particularly when the patient has already received an anti-angiogenic-based combination up-front. In the following pages we described the biological scenario validating second-line angiogenesis inhibition in colorectal cancer along with potential mechanism of resistance. We also critically described the available evidence recommending the use of the bevacizumab, aflibercept and ramucirumab in this setting with the final aim to guide the choice in the clinical practice.

Advances and perspectives of colorectal cancer stem cell vaccine

Colorectal cancer is essentially an environmental and genetic disease featured by uncontrolled cell growth and the capability to invade other parts of the body by forming metastases, which inconvertibly cause great damage to tissues and organs. It has become one of the leading causes of cancer-related mortality in the developed countries such as United States, and approximately 1.2 million new cases are yearly diagnosed worldwide, with the death rate of more than 600,000 annually and incidence rates are increasing in most developing countries. Apart from the generally accepted theory that pathogenesis of colorectal cancer consists of genetic mutation of a certain target cell and diversifications in tumor microenvironment, the colorectal cancer stem cells (CCSCs) theory makes a different explanation, stating that among millions of colon cancer cells there is a specific and scanty cellular population which possess the capability of self-renewal, differentiation and strong oncogenicity, and is tightly responsible for drug resistance and tumor metastasis. Based on these characteristics, CCSCs are becoming a novel target cells both in the clinical and the basic studies, especially the study of CCSCs vaccines due to induced efficient immune response against CCSCs. This review provides an overview of CCSCs and preparation technics and targeting factors related to CCSCs vaccines in detail.