The use of histotripsy as intratumoral immunotherapy beyond tissue ablation—the rationale for exploring the immune effects of histotripsy

Figures & data

Figure 1. Typical acoustic pressure waveform for mechanical high-intensity focused ultrasound (M-HIFU) and thermal high-intensity focused ultrasound (T-HIFU). PRP: pulse repetition period, PD: pulse duration, DC: duty cycle.

Table 1. Sonication parameters for histotripsy-assisted cancer immunotherapy pre-clinical studies.

Model	Cell line	Target	Study	Transducer	Frequency	Pressure	Pulse duration	Cycle number	Pulse repetition frequency	Pulse repetition period	Duty cycle	Pulses number	Ref
N/A	MDA-MB-231	Breast cancer	In vitro	Extracorporeal	2 MHz	P+: 85 MPa P_: 14 MPa	10 ms	20,000	1 Hz	1 s	1%	5, 25, 50, 100, 200	35
C57BL/6 Mice	B16GP33, Hepa1–6	Melanoma, hepatoma	In vivo	Extracorporeal	1 MHz	P_: 30 MPa	N/A	N/A	100 Hz	10 ms	N/A	50	49
C57BL/6 Mice	B16F10, Hepa1–6	Melanoma, hepatoma	In vivo	Extracorporeal	1 MHz	P_: 30 MPa	N/A	N/A	100 Hz	10 ms	N/A	50	44
Sprague Dawley Rats	McA-RH7777	Liver cancer	In vivo	Extracorporeal	1 MHz	P+: 43.9 MPa P_: 37.8 MPa	1–2 μs	1–2	100 Hz	10 ms	0.01%-0.02%	18,000–30,000	41
Sprague Dawley Rats	N1–S1	Hepatocellular	In vivo	Extracorporeal	1 MHz	P_: >30 MPa	1 μs	1	100 Hz	10 ms	0.01%	2000–3000	38
Dog	N/A	Osteos-arcoma	In vivo	Extracorporeal	500 kHz	P_: 20 MPa	N/A	N/A	N/A	N/A	N/A	500/each point	42
C57BL/6, BALB/c Mice	MM3MG-HER2	Breast cancer	In vivo	Extracorporeal	1.5 MHz	N/A	4 ms	6,000	5 Hz	200 ms	2%	N/A	39
NCr Nude Mice	NGP	Neuroblastoma	In vivo	Extracorporeal	1 MHz	P_: 35 MPa	2 μs	2	50 Hz	20 ms	0.01%	N/A	43
C57BL/6 Mice	MC38	Colorectal carcinoma	In vivo	Intracorporeal	25.72 kHz	N/A	N/A	N/A	150 Hz	6.67 ms	50%	N/A	50

P₊: peak positive pressure, P_{_}: peak negative pressure.

Figure 2. Combination of M-HIFU and PD-L1 blockade enhanced the abscopal effect but could not eradicate distant tumors in a bilateral MM3MG-HER2 model. MM3MG-HER2 cells were implanted into the right thigh and left flank of BALB/c mice. Seven days later, M-HIFU was administered to right thigh tumors in the M-HIFU monotherapy and combination therapy groups. Anti-PD-L1 antibody (100 µg/inj) or isotype control IgG was intraperitoneally injected on days 10, 13 and 16. Tumor growth curves for treated and untreated tumors are shown. Data represent results from 2 pooled experiments. n = 13–19 per group; error bar, mean ± SD; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

Figure 3. Schematic of intratumoral histotripsy immunotherapy. (A) Intratumoral sonication using an intracorporal, miniaturized ultrasound device. (B) Histotripsy-induced tumor cell necrosis and corresponding immunomodulation. Created with biorender.com.

Data availability statement

Raw data were generated at Duke University and North Carolina State University. Derived data supporting the findings of this study are available from the corresponding author [HKL] on request.