Water bath hyperthermia reduces stemness of colon cancer cells

Researchers have proposed that cancer stem cells (CSCs) are the driving force of tumorigenesis, recurrence, and metastases, contributing to the failure of some cancer treatments. Water bath hyperthermia, a novel treatment for cancer, can be highly effective when combined with chemotherapy, radiotherapy, or immunotherapy. Side population (SP) cells are part of a subpopulation of cells that have stem cell-like characteristics. In preliminary experiments, we discovered a decrease in SP cells in heat-treated colon cancer cells, which encouraged us to investigate whether hyperthermia had in fact played a role in regulating the stemness of colon cancer cells.

We determined the number of SP cells and CD133-positive cells using flow cytometry; surveyed the expression of stemness-related genes and proteins by using quantitative reverse transcriptase-polymerase chain reaction and Western blot analysis, respectively; and evaluated tumor formation ability by using the tumor sphere formation assay.

We found that water bath hyperthermia at 40 °C results in a decreased percentage of SP cells (i.e. decreased from 0.6% to 0.0% and 1.1% to 0.1% among heat-treated HCT116 cells and SW620 cell respectively) and CD133-positive cells (i.e. decreased from 25.1 ± 1.2% to 18.7 ± 1.3% and 33.6 ± 3.2% to 23.5 ± 2.5% among heat-treated HCT116 cells and SW620 cell separately), weakens stem cell self-renewal properties (i.e., tumor colony formation ability), and downregulates the expression of stem-like cellular markers in colon cancer cells.

All the findings indicate that hyperthermia has an important effect on the stemness of colon cancer cells.