Can ultrasound irradiation be a therapeutic option for prostate cancer?

Abstract

BackgroundFocal therapies for prostate cancer (PC) can reduce adverse events and do not lead to androgen‐independent progression. Ultrasound could be used for cancer treatments if the repetition frequency is fitted to the purpose. We investigated the possible therapeutic effect of ultrasound irradiation on PC cells.Materials and MethodsWe irradiated two PC cell lines, androgen‐dependent LNCaP and ‐independent PC‐3 with ultrasound (3.0 W/cm2, 3 MHz, irradiation time rate: 20%) for 2 minutes for 1 day or 3 consecutive days at a repetition frequency of 1, 10, or 100 Hz in vitro. Cell proliferation and apoptosis were determined after irradiation.ResultsCell proliferation of PC‐3 was significantly inhibited after 1 day (P < .0001) and 3 days (P < .0001) of 10 Hz ultrasound irradiation, and that of LNCaP after 1 day (P < .0001) and 3 days (P < .0001) of irradiation. LNCaP was more sensitive to ultrasound at both lower and higher cell density but PC‐3 was only sensitive at a lower cell density (P < .01). Irradiation with 10 Hz ultrasound‐induced significantly more PC‐3 apoptotic cells than control (1 day, P = .0137; 3 days, P = .0386) rather than irradiation with 1 Hz. Apoptosis via caspase‐3 was induced at 10 Hz in 1‐day (P < .05) irradiation in both cell lines.ConclusionsUltrasound irradiation with even 1 day of 10 Hz significantly inhibited cell proliferation in both LNCaP and PC‐3, especially by the remarkable induction of apoptosis in vitro. Our study indicated that ultrasound irradiation can be a therapeutic option for PC and further studies in vivo will be undertaken.

Proapoptotic effect of nonthermal pulsed ultrasound on prostate cancer cells in a nude mouse model

“…The current results show that LNCaP and PC‐3 differ in therapeutic efficacy in vitro, specifically that PC‐3 may be resistant to treatment compared to LNCaP. This trend has been suggested in previous reports 6 . Differences in efficacy by cell type are observed despite the fact that the treatment mechanism is mechanical stimulation, which has also been reported for X‐ray radiation 20 and HIFU combined with radiotherapy 21 .…”

“…This trend has been suggested in previous reports. 6 Differences in efficacy by cell type are observed despite the fact that the treatment mechanism is mechanical stimulation, which has also been reported for X-ray radiation 20 and HIFU combined with radiotherapy. 21 Not only by cell type but also by time after US irradiation, the therapeutic effect has been observed to vary.…”

“…5 The cavitation effects also induce apoptosis and necrosis, the therapeutic effect of US irradiation. 3 We have previously reported that optimizing the pulse repetition frequency (PRF) of nonthermal US has antitumor effects on prostate cancer cells 6 and could enhance therapeutic efficacy in a wild-type mouse model. 7 Our nonthermal US mode has an advantage over HIFU by avoiding treatment risks such as stricture, achieving its antitumor effects solely by cavitation.…”

Ultrasound-mediated microbubbles cavitation enhanced chemotherapy of advanced prostate cancer by increasing the permeability of blood-prostate barrier

“…However, an in vitro study conducted by Maeshige et al. reported that PC-3 and LNCaP cells proliferation was significantly inhibited by US irradiation (3.0 W/cm 2 , 3 MHz) [33] . This seems to be inconsistent with our results.…”

Combined Treatment with Ultrasound and Immune Checkpoint Inhibitors for Prostate Cancer

“…Thus, the outcomes of ICI monotherapy are inadequate due to the poor immunological circumstance [5]. Recently, we found that US irradiation of PC cell lines can induce apoptosis without thermal damage to cancer cells [6]. If the antitumor effect of ICIs on PC is upregulated in the combination treatment with US irradiation, a less invasive and effective treatment of ICIs in clinical practice can be performed.…”