Ultrasound-triggered microbubble destruction enhances the radiosensitivity of glioblastoma by inhibiting PGRMC1-mediated autophagy in vitro and in vivo

Background:Ultrasound-triggered microbubble destruction(UTMD) is a widely used noninvasive technology in both military and civilian medicine,which could enhance radiosensitivity of various tumors.However,little information is available regarding the effects of UTMD on radiotherapy for glioblastoma or the underlying mechanism.This study aimed to delineate the effect of UTMD on the radiosensitivity of glioblastoma and the potential involvement of autophagy.Methods:GL261,U251 cells and orthotopic glioblastoma-bearing mice were treated with ionizing radiation(IR) or IR plus UTMD.Autophagy was observed by confocal microscopy and transmission electron microscopy.Western blotting and immunofluorescence analysis were used to detect progesterone receptor membrane component 1(PGRMC1),light chain 3 beta 2(LC3B2) and sequestosome 1(SQSTM1/p62) levels.Lentiviral vectors or siRNAs transfection,and fluorescent probes staining were used to explore the underlying mechanism.Results:UTMD enhanced the radiosensitivity of glioblastoma in vitro and in vivo(P<0.01).UTMD inhibited autophagic flux by disrupting autophagosome-lysosome fusion without impairing lysosomal function or autophagosome synthesis in IR-treated glioblastoma cells.Suppression of autophagy by 3-methyladenine,bafilomycin A1 or ATG5 siRNA had no significant effect on UTMD-induced radiosensitization in glioblastoma cells(P<0.05).Similar results were found when autophagy was induced by rapamycin or ATG5 overexpression(P>0.05).Furthermore,UTMD inhibited PGRMC1expression and binding with LC3B2 in IR-exposed glioblastoma cells(P<0.01).PGRMC1 inhibitor AG-205 or PGRMC1siRNA pretreatment enhanced UTMD-induced LC3B2 and p62 accumulation in IR-exposed glioblastoma cells,thereby promoting UTMD-mediated radiosensitization(P<0.05).Moreover,PGRMC1 overexpression abolished UTMD-caused blockade of autophagic degradation,subsequently inhibiting UTMD-induced radiosensitization of glioblastoma cells.Finally,compared with IR plus UTMD group,PGRMC1 overexpression significantly increased tumor size [(3.8±1.1) mm^(2)vs.(8.0±1.9) mm^(2),P<0.05] and decreased survival time [(67.2±2.6) d vs.(40.0±1.2) d,P=0.0026] in glioblastoma-bearing mice.Conclusions:UTMD enhanced the radiosensitivity of glioblastoma partially by disrupting PGRMC1-mediated autophagy.

Ultrasound-induced biophysical effects in controlled drug delivery

Ultrasound is widely used in biomedical engineering and has applications in conventional diagnosis and drug delivery.Recent advances in ultrasound-induced drug delivery have been summarized previously in several reviews that have primarily focused on the fabrication of drug delivery carriers.This review discusses the mechanisms underlying ultrasound-induced drug delivery and factors affecting delivery efficiency,including the characteristics of drug delivery carriers and ultrasound parameters.Firstly,biophysical effects induced by ultrasound,namely thermal effects,cavitation effects,and acoustic radiation forces,are illustrated.Secondly,the use of these biophysical effects to enhance drug delivery by affecting drug carriers and corresponding tissues is clarified in detail.Thirdly,recent advances in ultrasound-triggered drug delivery are detailed.Safety issues and optimization strategies to improve therapeutic outcomes and reduce side effects are summarized.Finally,current progress and future directions are discussed.