Improving the Therapeutic Effect of Ultrasound Combined With Microbubbles on Muscular Tumor Xenografts With Appropriate Acoustic Pressure

Ultrasound combined with microbubbles (USMB) is a promising antitumor therapy because of its capability to selectively disrupt tumor perfusion. However, the antitumor effects of repeated USMB treatments have yet to be clarified. In this study, we established a VX2 muscular tumor xenograft model in rabbits, and performed USMB treatments at five different peak negative acoustic pressure levels (1.0, 2.0, 3.0, 4.0, or 5.0 MPa) to determine the appropriate acoustic pressure. To investigate whether repeated USMB treatments could improve the antitumor effects, a group of tumor-bearing rabbits was subjected to one USMB treatment per day for three consecutive days for comparison with the single-treatment group. Contrast-enhanced ultrasonic imaging and histological analyses showed that at an acoustic pressure of 4.0 MPa, USMB treatment contributed to substantial cessation of tumor perfusion, resulting in severe damage to the tumor cells and microvessels without causing significant effects on the normal tissue. Further, the percentages of damaged area and apoptotic cells in the tumor were significantly higher, and the tumor growth inhibition effect was more obvious in the multiple-treatment group than in the single USMB treatment group. These findings indicate that with an appropriate acoustic pressure, the USMB treatment can selectively destroy tumor vessels in muscular tumor xenograft models. Moreover, the repeated treatments strategy can significantly improve the antitumor effect. Therefore, our results provide a foundation for the clinical application of USMB to treat solid tumors using a novel therapeutic strategy.

Upregulation of ULK1 expression in PC-3 cells following tumor protein P53 transfection by sonoporation

The aim of the present study was to investigate whether ultrasound combined with microbubbles was able to enhance liposome-mediated transfection of genes into human prostate cancer cells, and to examine the association between autophagy and tumor protein P53 (P53). An MTT assay was used to evaluate cell viability, while flow cytometry and fluorescence microscopy were used to measure gene transfection efficiency. Autophagy was observed using transmission electron microscopy. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis were used to assess the expression of autophagy-associated genes. The results of the present study revealed that cell viability was significantly reduced following successfully enhanced transfection of P53 by ultrasound combined with microbubbles. In addition, serine/threonine-protein kinase ULK1 levels were simultaneously upregulated. Castration-resistant prostate cancer is difficult to treat and is investigated in the present study. P53 has a significant role in a number of key biological functions, including DNA repair, apoptosis, cell cycle, autophagy, senescence and angiogenesis. Prior to the present study, to the best of our knowledge, increased transfection efficiency and reduced side effects have been difficult to achieve. Ultrasound is considered to be a 'gentle' technique that may be able to achieve increased transfection efficiency and reduced side effects. The results of the present study highlight a potential novel therapeutic strategy for the treatment of prostate cancer.

Upregulation of Beclin-1 expression in DU-145 cells following low-frequency ultrasound irradiation combined with microbubbles

Castration-resistant prostate cancer (PCa) is difficult to treat. Autophagy, which is an evolutionarily conserved mechanism, plays an important role in cancer development. The balance between cell death and survival in different stages varies in cancer development. The role of autophagy in PCa development has not yet been fully elucidated. Ultrasound may be of value in the treatment of PCa. The aim of the present study was to investigate the association between autophagy and ultrasound combined with microbubbles. The MTT assay was used to evaluate cell viability. Autophagy was observed by transmission electron microscopy. Reverse transcription-polymerase chain reaction and western blot analysis were used to assess the expression of autophagy-related genes. The results revealed that cell viability was significantly reduced by ultrasound combined with microbubbles in DU145 PCa cells. The present study demonstrated that ultrasound combined with microbubbles induced autophagy and autophagy-related DU-145 cell death. Notably, these findings highlighted additional mechanisms that suggest the potential of ultrasound-modulated autophagy as a novel therapeutic strategy for PCa.