Sononeoperfusion: a new therapeutic effect to enhance tumour blood perfusion using diagnostic ultrasound and microbubbles

Abstract

Background Hypoperfusion or resultant hypoxia in solid tumours is a main reason for therapeutic resistance. Augmenting the blood perfusion of hypovascular tumours might improve both hypoxia and drug delivery. Cavitation is known to result in microstreaming and sonoporation and to enhance drug diffusion into tumours. Here, we report the ability to enhance both tumour blood perfusion and doxorubicin (Dox) delivery using a new sononeoperfusion effect causing a cavitation effect on tumour perfusion in subcutaneous Walker-256 tumours of rats using ultrasound stimulated microbubble (USMB). Methods To induce the sononeoperfusion effect, USMB treatment was performed with a modified diagnostic ultrasound (DUS) system and SonoVue® microbubbles. The therapeutic pulse was operated with a peak negative pressure of 0.26 to 0.32 MPa and a pulse repetition frequency (PRF) of 50 Hz to 2 kHz. Contrast-enhanced ultrasound (CEUS) was used for tumour perfusion assessment. Results The USMB treatment of 0.26 MPa and 1 kHz could significantly enhance tumour perfusion with a 20.29% increase in the CEUS peak intensity and a 21.42% increment in the perfusion area for more than 4 hours (P < 0.05). The treatment also increased Dox delivery to tumours by approximately 3.12-fold more than that of the control (P < 0.05). Furthermore, ELISAs showed that vasodilators and inflammatory factors increased 4 hours after treatment (P < 0.05), suggesting that the inflammatory response plays an important role in the sononeoperfusion effect. Conclusion The USMB-induced sononeoperfusion effect could significantly enhance the blood perfusion of Walker-256 tumours and promote drug delivery. It might be a novel physical method for overcoming the therapeutic resistance of hypoperfused or hypoxic tumours.

Sononeoperfusion effect by ultrasound and microbubble promotes nitric oxide release to alleviate hypoxia in a mouse MC38 tumor model

“…Lindner found that NO release is related to muscles sonoreperfusion [20] . Our previous study also found increased NO and eNOS post USMB [7] . This study demonstrated that the NO concentration significantly increased post USMB treatment ( Figure 2 H).…”

“…In this study, we applied a novel approach using DUS and microbubbles to enhance tumor blood perfusion, called “sononeoperfusion effect.” It improved pO 2 of the tumor tissue, decreased HIF-1α and D-LA levels, and improved the hypoxic microenvironment by releasing NO ( Table 1 ). Our previous studies found that sononeoperfusion can enhance tumor perfusion and therapeutic outcomes in several animal models, including rat Walker-256 breast cancer, rabbit VX2 tumor, nude mouse PANC-1 pancreatic cancer, and mouse MC38 colon cancer [7] , [8] , [10] , [14] . Remarkably, we found that HIF-1α concentration decreased post USMB in rabbit VX2 tumor [8] .…”

“…We found that a low mechanical index (MI) diagnostic ultrasound (DUS) combined with microbubbles (contrast agent) could improve tumor blood perfusion, called “sononeoperfusion effect” [7] . Enhanced tumor perfusion improves the therapeutic effect.…”

“…Enhanced tumor perfusion improves the therapeutic effect. In chemotherapy, the drug concentration in tumor tissue was elevated by up to 3.12-fold in rat Walker-256 breast cancer (doxorubicin) and 2.83-fold in rabbit VX2 tumors (gemcitabine) [7] , [8] , and tumor growth was inhibited in rabbit VX2 tumors [9] . In immunotherapy, the sononeoperfusion effect resulted in tumor growth inhibition and longer survival in mice with MC38 colon cancer [10] .…”

“…The required ultrasound intensity was extremely low according to the FDA and IEC guidelines. Our previous studies have primarily found that the expression of nitric oxide (NO), endothelial nitric oxide synthase (eNOS), and adenosine-triphosphate (ATP) were increased and hypoxia-inducible factor-1α (HIF-1α) was decreased post treatment [7] , [8] . Therefore, the effect of sononeoperfusion may be related to NO release, leading to the hypoxia amelioration.…”