Immunomodulation of prostate cancer cells after low energy focused ultrasound
© Skalina et al; licensee BioMed Central Ltd. 2015
Published: 30 June 2015
LOFU treatment was performed on the Philips Therapy and Imaging Probe System (TIPS, Philips Research Briarcliff, USA) using 3W, 100% duty cycle, 1.5 seconds, 1 mm spacing. For IF analysis, LOFU-treated cells were cytospined and fixed with 4% paraformaldehyde and stained with rabbit ant-HSP70 overnight, followed by incubation with a secondary goat anti-rabbit PE conjugated and anti-phalloidin antibodies for 1 hour at room temperature. DAPI was included in the mounting medium and slides were analyzed using an Inverted Olympus IX81. Flow cytometry staining included a live/dead cell marker to isolate only living cells expressing HSP70 on the cell surface.
Results and conclusions
The immunomodulatory effect of LOFU was analyzed on prostate cancer cell lines, both human and murine, by detecting the surface expression of HSP70 and calreticulin by flow cytometry & immunofluorescence (IF) six hours following LOFU treatment of a cell pellet. LOFU significantly induced cell surface HSP70 expression and calreticulin in vitro in human and mouse prostate cancer cell lines, as shown by flow cytometry (Figure 1C) and confirmed by IF (Figure 1D). Surface HSP70 is a danger signal which can activate dendritic cells to induce an anti-tumor immune response. Surface calreticulin acts as a “eat me” signal for phagocytic cells, resulting in increased phagocytosis and antigen processing. Immunomodulation by LOFU can attract DCs to the tumor and induce a Th1 predominant immune response.
This research was supported by the MSTP training grant (T32-GM007288).
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