Proton beam irradiation suppresses metastatic capabilities of human cancer cells

Abstract

Proton radiotherapy has been established as a highly effective modality for the local control of tumor growth. Proton therapy has the advantage over conventional photon beam in that the tumor can be targeted with extreme precision without harming healthy surrounding tissue. The eradication of the metastatic potential of cancer cells is crucial for achieving survival in most patients with cancer. We examined the biological properties of human colorectal adenocarcinoma cells after irradiation with a proton beam to assess their metastatic processes by measuring the cell’s capability to adhere to an extracellular matrix, the expression of integrins, and cell migration. Cell adhesion assays were done to assess cancer cell’s capabilities to adhere to an extracellular matrix, and the capability of human colorectal adenocarcinoma cells irradiated with a proton beam to adhere to an extracellular matrix was large than that of adenocarcinoma cells that had not been irradiated. The mean fluorescence intensity of integrins, which plays a crucial role in cell adhesion to extracellular matrix and cell migration, was analyzed by using flow cytometry analyses. The expression level of β1 integrin was increased after proton beam irradiation. However, the amount of ανβ3 integrin was not changed by proton irradiation. Treatment of human colorectal adenocarcinoma cells with increasing doses of proton irradiation led to a dose-dependent decrease in cell migration. Our data indicated that the metastatic capabilities of human colorectal adenocarcinoma cells may be suppressed by using proton irradiation, which inhibits cancer cell adhesion and migration.