Pulsed Electromagnetic Field Therapy Alters the Genomic Profile of Bladder Cancer Cell Line HT-1197

Abstract

Background/Objectives: Pulsed electromagnetic field (PEMF) therapy involves the use of magnetic waveform energy for targeted treatment delivery. This technique has shown promising results in the treatment of various cancers. Currently, treatment of bladder cancer is highly invasive, involving intravesical chemotherapy or radical cystectomy. The potential therapeutic effects of PEMF therapy on bladder cancer are a relatively new and understudied area; therefore, the goal of this investigation was to gain mechanistic insight by examining the effects of PEMF therapy on a bladder cancer cell line in vitro. Methods: Cells from the bladder cancer cell line HT-1197 were cultured and incubated with (treatment group) or without (control group) PEMF therapy for one hour each day for five days. Cell counts were compared using Incucyte^® data to determine proliferation rates. At days 1 and 5, total RNA was isolated from cells, and following quantity and quality checks, gene expression was compared between the two groups. Proliferation rates from cell line HT-1197 were compared to prior published results on the bladder cancer cell line HT-1376. Results: HT-1197 cells treated with PEMF therapy had slower proliferation rates compared to controls (p < 0.05), but HT-1376 cells did not (p > 0.05). Principal component analysis showed complete separation of treated and untreated cells, with PEMF treatment accounting for 76% of the variation between the groups. Expression of numerous genes and cancer-related pathways was altered in the treated cells relative to the controls. Conclusions: Bladder cancer HT-1197 cells treated with PEMF therapy had slower proliferation and corresponding changes in gene expression. Several cancer-relevant pathways were differentially regulated following PEMF treatment. The conclusions are limited by the lack of a control healthy urothelial cell line in the experiments. Despite this shortcoming, our results suggest that PEMF therapy may be a promising avenue for further research in the treatment of bladder cancer.

Keywords: HT-1197; bladder cancer; non-invasive; pulsed electromagnetic field therapy; therapeutic; urology.

Figure 1

Mutations of bladder cancer cell line HT-1197. Tumor stage, grade, and histology are shown. Additionally, relevant genes that are either wild type or mutated are reported, with a legend corresponding to each gene. Figure adapted from Rasheed et al. [11].

Figure 2

Experimental setup for pulsed electromagnetic field therapy administration. A Helmholtz coil was placed inside a temperature-controlled incubator. During treatment sessions, the culture plates containing the HT-1197 cells were placed at the same locale within the magnetic field, which was verified with a gauss meter. The field of treatment was determined to be uniform over the entire area of the culture plates.

Figure 3

HT-1197 cells in culture. HT-1197 bladder cancer cells prior to beginning the experiment under a microscope at 10x magnification. Cells can be seen in clusters intact growing appropriately before the experiment was started. Both PEMF and control cells came from this cell line. A scale is provided in the bottom-right corner of the figure.

Figure 4

Cell growth curves. Representation of the exponential growth curves of both the control (blue) and PEMF-treated cells (orange). The x-axis is time from the start of the experiment in hours and cell count is on the y-axis. The 0:00:00 time point represents the start of PEMF treatment on day one of the experiment. On both curves, “e” represents Euler’s number, a constant value of 2.718281828459. (a) Exponential growth lines with equations are provided for HT-1197 PEMF and control cells. (b) Exponential growth lines with equations are provided for HT-1376 PEMF and control cells.

Figure 5

Principal component analysis and hierarchical clustering. (a) PCA was performed using gene expression profiles from control (purple) and experimental (green) samples. (b) Hierarchical clustering revealed 49 DETs between the groups. “None” represents the control cells and “PEMF” the experimentally treated cells. Red represents upregulated DETs (PEMF vs. control) and blue downregulated.

Figure 6

Cancer-relevant pathways. (A) The cancer drug resistance efflux pathway was downregulated in PEMF-treated cells. It normally works to remove the concentration of cancer drug inside a tumor cell. (B) The G1/S checkpoint regulation pathway, which acts to halt the cell cycle when damage to DNA is detected, was upregulated in PEMF-treated cells. (C) The PI3K/AKT pathway normally acts to promote cell survival and proliferation when activated. It was downregulated in PEMF-treated cells. Figure created with BioRender.com.