Research ArticleExperimental Studies
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Non-thermal Acoustic Enhancement of Chemotherapeutic Effects of Cisplatin on Xenografted Cervical Cancer in Mice

SEUNG-SCHIK YOO, PERRY KATSARAKES, JASON GASHI, EVGENII KIM, HYUN-CHUL KIM and MARK BÖHLKE
Anticancer Research November 2023, 43 (11) 4793-4800; DOI: https://doi.org/10.21873/anticanres.16676

Abstract

Background/Aim: We examined the effect of low-intensity focused ultrasound (FUS) on unbinding cisplatin from plasma proteins and enhancing its chemotherapeutic efficacy using a mouse model of xenograft human cervical cancer. Materials and Methods: FUS, operating in a pulsed mode, was applied to a dialysis cassette immersed in a normal saline bath containing both bovine serum albumin (BSA) and cisplatin, and the unbound level of cisplatin diffused into the cassette was measured. To assess the in vivo efficacy of the technique, athymic nu/nu mice were inoculated with human cervical cancer cells under four different combinatory conditions, with and without the administration of cisplatin and FUS. FUS was delivered to the tumor mass for 1 h across four separate sessions spanning a period of 10 days, following the intraperitoneal injection of cisplatin. Results: In vitro equilibrium dialysis revealed that non-thermal application of FUS increased the concentration of unbound cisplatin compared to cassettes that were not exposed to sonication, suggesting successful unbinding. Assessment of tumor growth in vivo showed that FUS following cisplatin administration resulted in a significant reduction in tumor growth, whereas the administration of cisplatin alone exhibited plateau growth. Without administration of cisplatin, equivalent rates of aggressive tumor growth were observed regardless of the application of FUS. Conclusion: Pulsed application of FUS can unbind cisplatin from albumin and enhance its tumoricidal effects in cervical cancer. Further assessment of intratumoral/systemic cisplatin concentration is required to quantify its selective delivery to the tumor.

Key Words:

Maximal delivery of chemotherapeutic drugs to a malignant tumor in a region-specific manner is critical for the successful treatment of cancer. When introduced into the bloodstream, many types of chemotherapeutic drugs [e.g., platinum(Pt)- and taxane-based agents] bind to plasma proteins (e.g., albumin, α-1 acid glycoprotein, and globulin) with high binding rates (>90%) (1). When bound to plasma proteins, drug molecules remain sequestered within the bloodstream, profoundly reducing their bioavailability in the tumor interstitium (2, 3).

This drug-plasma protein binding (PPB) is known to be mediated by weak molecular interactions such as van der Waals and non-covalent electrostatic (hydrogen bonds) forces (4), which are relatively weak (on the order of piconewtons) and rapidly reversible (5, 6). The strength and extent of PPB generally depend on the molecular/chemical properties of drugs, and the binding rate has been considered unchangeable (listed as one of the drug characteristics) except for the presence of physiological [e.g., pregnancy (7)] or pathological conditions [e.g., renal disease (8)], or drug–drug interactions [e.g., displacement of warfarin by nonsteroidal anti-inflammatory drugs from albumin binding (9)]. To avoid the effects of PPB, surface modification of drug molecules or development of delivery vehicles (e.g., liposomes or nano-particle carriers) have been pursued (10, 11); however, these methods require a lengthy development time before reaching the clinic. To maximize effective delivery of a drug in its unmodified form, a new technique is sought to unbind the drug from plasma proteins only in the tumor and its surrounding margins.

Application of non-ionizing, non-thermal mechanical force generated by pulsed low-intensity ultrasound pressure waves to the drug-plasma protein complex was found to temporarily disrupt PPB, consequently increasing the amount of unbound (‘free’) drug molecules available to the tissue without elevating the systemic concentration (12-15). Investigations have revealed that acoustic pressure waves applied to a local region of tissue (of the order of 400 kPa) can impose a non-thermal radiation force greater than the binding force [Kim et al. (13) for theoretical derivations for albumin and α-1-acid glycoprotein], leading to temporary unbinding of a drug from plasma proteins, which raises its ‘effective’ unbound concentration. When delivered in a focal manner, known as focused ultrasound (FUS), acoustic waves can be directed to a highly localized area of the tissue with flexibility in controlling the depth and size of the focus (16).

By combining these properties, we examined whether the application of FUS can locally disrupt cisplatin-albumin binding, thus enhancing its tumoricidal effects. Among chemotherapeutic agents, cisplatin was chosen due to its high binding rate to albumin (>95%) along with its well-studied PPB properties and tumoricidal effects on advanced-stage cervical cancer (17). The study consisted of two separate experimental segments: 1) an in vitro equilibrium dialysis experiment that evaluated whether FUS can unbind cisplatin from albumin and 2) an in vivo assessment of the enhanced tumoricidal effects of cisplatin in a mouse xenograft model of cervical cancer.

Materials and Methods

FUS system. Two types of FUS transducers were used in this study. For the in vitro experiment examining the effects of pulsed FUS on cisplatin-BSA unbinding, we used a single-element FUS operated at 250 kHz (GS200-D25, Ultran Group, State College, PA, USA). For the in vivo experiment, we used a transducer (GPS200-D40) that operated at a slightly lower frequency (200 kHz) and formed a larger focal size to encompass a tumor mass. The acoustic intensity profiles of FUS generated from each transducer were mapped using a needle-type hydrophone (HNC200, Onda Corp., Sunnyvale, CA, USA) attached to 3-axis robotic stages (Bi-Slides Velmex). A detailed characterization of the acoustic field has been described previously (12). Pressure amplitude at the focus was calibrated with respect to the input sinusoidal waves by using a calibrated hydrophone at each frequency. For the in vitro experiment, the acoustic focus was formed 13 mm away from the exit plane of the transducer, with an ellipsoidal geometry of 5 mm in diameter and 13 mm in length [defined as the full width at half-maximum (FWHM) intensity; dotted red line in Figure 1A and B]. For the transducer used in the in vivo experiment, the acoustic focus, 9 mm in diameter and 26 mm in length, was formed 24 mm away from the exit plane of the transducer (dotted red line in Figure 1C and D). The sinusoidal electrical signals from the function generator were amplified using a linear amplifier (10 Watt, Electronics and Innovations, Rochester, NY, USA) with impedance matching.

Figure 1.
Figure 1.

Experimental setup for in vitro and in vivo experiments. (A) Longitudinal and (B) transversal intensity maps of the sonication focus (white dotted line) used in the equilibrium dialysis. The red dotted lines indicate the focal profile defined at the FWHM intensity. The white arrow: the direction of sonication. (C) and (D) are the intensity map from the transducer used in the animal experiment. (E) A sonication chamber for equilibrium dialysis experiment. (F) A FUS setup for sonicating the tumor at a unilateral flank of a mouse. The black arrow: tumor location.

In vitro equilibrium dialysis. The feasibility of unbinding cisplatin from albumin using pulsed low-intensity FUS was examined by sonicating a normal saline (NS) solution containing a therapeutic concentration of cisplatin [2.8 μg/ml (18, 19)] and physiological levels of bovine serum albumin (BSA, 45 mg/ml). The container housing that held the solution was 3D-printed, and the walls were lined with rubber pads to absorb acoustic waves. The container contained slots to insert dialysis cassettes (Slide-A-Lyzer, 7-kDa molecular weight cutoff pore size, Thermo Fisher Scientific, Waltham, MA, USA). The cassette only allowed unbound cisplatin to diffuse through the membrane via osmotic pressure, whereas albumin-bound cisplatin did not cross the membrane.

FUS was delivered to the front surface of the dialysis cassette membrane containing only NS (Figure 1E, labeled ‘FF’) for 30 min. The spatial-peak pulse-average intensity (ISPPA) was 5.0 W/cm2, and the corresponding peak negative pressure was 391 kPa [a mechanical index (MI) of 0.8, a measure of mechanical risk to biological tissue, <1.9 is recommended for diagnostic ultrasound imagers (20)]. Considering a 50% duty cycle of sonication, the spatial-peak temporal-average intensity (ISPTA) was 2.5 W/cm2. The use of a 50-ms pulse duration and a 10-Hz pulse repetition frequency was based on a non-thermal pulsing scheme that has been shown to unbind phenytoin from albumin at 250 kHz (12) and unbind lidocaine from α-1-acid glycoprotein at 500 kHz (13). Additional equilibrium dialysis cassettes were placed outside the sonication path (Figure 1E, ‘FO’) and in a region that was not exposed to sonication (Figure 1E, ‘C’ condition). Because temperature may affect PPB (3), the temperature of the bath was measured before and immediately after sonication. Cisplatin concentrations in the dialysates were determined using liquid chromatography with tandem mass spectrometry (HP1100 HPLC system, Agilent, Santa Clara, CA, USA) coupled to a triple quadrupole mass spectrometer (API4000Qtrap, AB/SCIEX, Framingham, MA, USA).

SiHa cell preparation for animal experiments. Human cervical squamous cell carcinoma cells (SiHa, HTB-35, ATCC, Manassas, VA, USA) were cultured in Dulbecco’s Modified Eagle’s medium (DMEM; make) containing 5% penicillin/streptomycin (Sciencell, Carlsbad, CA, USA) and 10% Fetal Bovine Serum (FBS; make). The cells were the screened for the presence of Corynebacterium bovis. The cells were harvested after four passages and suspended in Hanks’ Balanced Salt Solution (HBSS, make) at 107 cells per ml for inoculation. The viability of SiHa cells (>95%) was confirmed prior to implantation using a live/dead assay.

Mouse xenograft model. All experiments were conducted in accordance with the ethical guidelines of the Brigham and Women’s Hospital institutional animal care and use committee (BWH IACUC, approval number 2021N000239). Athymic nu/nu immunocompromised mice (n=20, all female, ~5-week-old on arrival, NU/J, homozygous for Foxn1, Jackson Lab, Bar Harbor, ME, USA) were housed under a 12 h/12 h light/dark cycle (lights on at 7 AM, off at 7 PM) and allowed access to food and water ad libitum. Only female mice were used due to estrogen-dependent SiHa growth and proliferation (21). Since orthotopic implantation of cervical cancer cells is extremely challenging in a mouse model, the mice were subcutaneously inoculated with SiHa cells (2×106 cells in 0.2 ml volume in HBSS) to the unilateral flank (side randomized) under isoflurane anesthesia (3% induction and ~1.5% for maintenance).

Nineteen out of 20 mice developed a visible tumor mass within four days, and the short- and long- axis lengths of the tumors were measured using a digital Vernier caliper to estimate the volume (assuming an ellipsoidal shape). When the length of the tumor (mean of long- and short-axis) reached >5 mm (~33 days after inoculation), the tumor-bearing mice were randomly assigned into four groups that underwent the following procedures: 1) receiving intraperitoneal (i.p.) injection of cisplatin only (n=5, days 0, 3, 7, and 10; Cis+/Us−, where ‘Us’ denotes the application of FUS), 2) receiving the same dose of cisplatin followed by the FUS to the site of the tumor (n=5, Cis+/Us+), 3) receiving FUS to the site of the tumor (n=4, in duration and frequency identical to Group 2) without receiving cisplatin (Cis−/Us+), and 4) receiving no treatment (n=5, Cis−/Us−). For the administration of cisplatin, a dose of 5 μg/g body weight was used (22) from a stock solution of cisplatin in normal saline (500 μg/ml).

For the application of FUS, animals were anesthetized using isoflurane inhalation (3% induction, 1-1.3% for maintenance), and FUS was applied to the tumor at ISPPA of 4 W/cm2 using a 50-ms pulse duration and a 5-Hz pulse repetition frequency (thus, 25% duty cycle, yielding ISPTA of 1 W/cm2) for 1 h, following the injection of cisplatin. The corresponding peak negative pressure was 345 kPa (MI of 0.8). The duty cycle, which was lower than that used in the in vitro study, was used to further reduce the risk of thermal/mechanical damage to the delicate skin. The timing (immediately following cisplatin injection) and duration of sonication (1 h) were determined based on the rapid reduction of the plasma concentration of cisplatin within 2-4 h after injection (23). Treatment intervals (days 0, 3, 7, and 10) were based on the half-life of serum cisplatin concentration [~100 h (18, 19)]. The acoustic waves from the transducer were coupled using compressible polyvinyl alcohol (PVA) hydrogel (9% by weight in distilled water) molded to cone-shaped housing [via two sets of freeze-thaw cycles (18 h-6 h each)], which has been shown to be effective in transferring acoustic pressure waves with negligible distortion (24), placing the acoustic focus over the tumor target (Figure 1F). The gel was contained in a cone-shaped plastic housing (23 mm length) and positioned ~1-2 mm away from the tumor surface. Ultrasound gel (Aquasonic 100, Parker Laboratory, Fairfield, NJ, USA) was applied between the interfaces. Although sonication was performed at a low intensity that did not elevate tissue temperature, we measured the skin temperature before and after each FUS session using an infrared thermal camera among Us+ groups (C3-X, Teledyne FLIR, Wilsonville, OR, USA). The tumor growth rate was measured until day 12 (time of sacrifice). Upon completion of the experimental procedure, all mice were euthanized (using i.p. injection of Euthasol), and each extracted tumor was weighed and photographed using a high-resolution flat-bed scanner (Epson Perfection V600 Photo, Epson, Suwa, Japan) in orthogonal dimensions (top and side views) to estimate the dimension of the tumor volume.

Statistical analysis. Statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). Normality and sphericity of the data distribution were assessed. The cisplatin concentration obtained from equilibrium dialysis was analyzed using a t-test. Non-parametric group comparisons were conducted with respect to each animal’s weight, estimated tumor volume, and the volume/weight of their extracted tumor.

Results

Equilibrium dialysis. The average cisplatin concentrations measured across the experimental conditions (n=10 each) are shown in Figure 2. Cisplatin concentration of the dialysates from the sonicated cassettes (‘FF’) was 2.03±0.28 μg/ml, which was significantly higher than that of the samples obtained outside of the focus (‘FO’ and ‘C’, 1.62±0.17 and 1.56±0.16 μg/ml respectively, paired t-test, p<0.001). The value was 24.9±4.8% and 30.1±8.4% higher than those from ‘FO’ and ‘C’, respectively. The bath temperature did not change during the dialysis (26.5±0.2 and 26.5±0.1°C, before and at the end of the sonication, p>0.3, paired t-test, n=10).

Figure 2.
Figure 2.

In vitro assessment of focused ultrasound-mediated cisplatin unbinding. Averaged concentration of dialyzed cisplatin across three locations of the cassettes (n=10 each): unsonicated control (‘C’), outside of the focus (‘FO’) and at the acoustic focus (‘FF’). Error bars: standard error. *p<0.001; paired t-test, one tail.

Mice experiment. Minor skin lesions associated with a protruding tumor mass were observed in two mice and resolved with application of topical zinc oxide lotion. All animals underwent all study procedures, except for one mouse in the Cis+/Us+ group, which died on day 8 of the procedure. An autopsy of the animal did not reveal any internal organ damage and death was deemed unrelated to sonication. The mean body weights of the animals are listed in Table I. To enable group comparison, the missing data pertaining to days 10 and 12 from the dead animals in the Cis+/Us+ group were substituted using the mean values obtained from the other four animals in the group.

View this table:
Table I.

Body weight of the animals (in grams, average±SD).

The animals in the cisplatin-treated groups lost body weight [χ2(4)=10.8, p<0.05, Friedman test] and the reduction was significant between the beginning of the FUS treatment and day 12 (p=0.018; Wilcoxon signed-rank test). In contrast, the other groups maintained their body weight [χ2(4) ≤7.7, p>0.1, Friedman test].

Skin temperature measurement (Table II) from the Us+ group showed that skin temperature was not affected by sonication (initial temperature, grand mean across each of the four sonication sessions, Cis+/Us+:Cis−/Us+=34.7±0.4:35.0±0.5°C, after sonication 34.7±0.6:34.6±0.6°C; all p>0.06, Wilcoxon signed rank test). The skin temperature was indistinguishable between the Cis+ and Cis− condition (all p>0.19, Mann–Whitney U-Test). Respiratory rates during the procedure were maintained at approximately 53 breaths/min across the groups (Cis+/Us+:Cis+/Us−:Cis−/Us+:Cis−/Us−=53.2±4.4: 53.4±6.1:53.0±3.9:53.4±3.6 per min, mean±standard deviation) and did not differ [χ2(4)=0.5, p=0.9, Kruskal–Wallis test].

View this table:
Table II.

Skin temperature (°C) before (Init) and after (end) the sonication (average±SD).

Evaluation of tumor growth rate. The time progression of percent changes in estimated tumor volumes with respect to the start of the intervention (day 0) across the experimental conditions is shown in Figure 3 (data shown in Table III). The estimated tumor volume decreased significantly over time with the application of FUS (that is, Cis+/Us+; ~70% reduction) compared to the group that only received cisplatin (Cis+/Us−), which showed a plateau rate of growth (~7%) after 12 days. In contrast, all Cis− conditions showed equivalent rates of steady increase in tumor volume (approximately 130%). Repeated ANOVA (Friedman) showed a consistent reduction in the Cis+/Us+ group [χ2(4)=18.5, p=0.001; n=5], whereas a consistent increase was observed in the Cis− groups [Cis−/Us+: Cis−/Us−=0.003, χ2(4)=16.0: 0.0005, χ2(4)=20.0, respectively]. Tumor growth in the Cis+/Us− group remained unchanged over time [χ2(4)=3.4, p=0.49]. Post-hoc comparison between Cis+/Us+ and Cis+/Us− revealed a reduction in tumor growth starting on day 3 (p=0.004, day 3; p=0.004, day 7; p=0.008, day 10; p=0.008, day 12; Mann–Whitney U-test).

Figure 3.
Figure 3.

In vivo evaluation of focused ultrasound on enhancing tumoricidal effects of cisplatin. Averaged percent growth of the tumor volume across four experimental conditions (Cis+/− and Us+/−) with respect to the first intervention. Error bars: standard error.

View this table:
Table III.

Percent change of estimated tumor volume with respect to day 0 (average±SD).

Volume and weight of extracted tumors across the groups. Photographs of the extracted tumors are shown in Figure 4. The weights and volumes of the extracted tumors (Table IV), albeit lower than those of any other group, were not significantly different between the Cis+/Us+ and Cis+/Us− groups (p>0.05, Mann–Whitney U-test). We noted that a tumor extracted from the Cis+/Us™ group contained a cyst (ID#1, Figure 4), which was deflated during the measurement, reducing its size and weight. The values from the Cis+/Us+ group were significantly smaller than those from the two Cis− groups (p<0.03, via Wilcoxon rank sum test).

Figure 4.
Figure 4.

Extracted tumor upon sacrificing the animals. Pictures (top and side view) of extracted tumors harvested on day 12 from the start of the intervention. A tumor extracted from one animal prematurely on day 8 (from Cis+/Us+) is shown in dashed box. The cystic tumor extracted from ID1 of the Cis+/Us− was deflated after the extraction (in arrows).

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Table IV.

Tumor weight (mg) and estimated volume (μl) obtained at sacrifice (average±SD).

Discussion

Although early detection and preventive measures (e.g., human papillomavirus vaccines) have lowered new diagnoses in the U.S., cervical cancer remains the 4th most common type of cancer in women, affecting nearly 13,000 new patients and causing approximately 4,000 deaths per year, with high ethnic/racial disparity worldwide (25). Early-stage treatment strategies include surgery (cryotherapy, loop electrosurgical excision, and laser ablation) and radiotherapy, whereas more advanced stages are approached via chemotherapy and concurrent radiotherapy, with the addition of anti-angiogenic medication (26). Among chemotherapeutic agents for cervical cancer (including paclitaxel and topotecan), cisplatin is considered the most effective in treating advanced cervical cancer (both recurrent and metastatic) (27). Its mechanism of action involves the formation of adducts with DNA that suppress the cell cycle, leading to apoptotic/necrotic activities (28). Due to its excellent tumoricidal potency, cisplatin is also used to treat other types of cancers (e.g., ovarian and breast cancers) (29).

The high binding rate of cisplatin to plasma albumin (>95%) (1) profoundly reduces its bioavailability. Increasing the systemic dose is an option to increase cisplatin delivery but is accompanied by higher risks for side effects (nephrotoxicity and vasculitis) (30). This conundrum warrants a new noninvasive technique to unbind cisplatin from albumin in a region-specific manner, which increases the delivery of unbound cisplatin to the targeted tumor. In this study, we conducted a preliminary investigation to demonstrate that the pulsed application of FUS unbinds cisplatin from albumin based on equilibrium dialysis and reduces both volume and growth of xenografted cervical cancer tumors in mice.

The results obtained from equilibrium dialysis suggest that a 30-min application of low-intensity FUS successfully unbound cisplatin from BSA, allowing for ~30% higher concentration of cisplatin to be diffused into the equilibrium cassettes. To achieve this level of unbound cisplatin concentration, an effective systemic dose of at least 3.5 μg/ml would have been required (instead of 2.8 μg/ml), which might have greatly elevated the risks for side effects such as nephrotoxicity (30). The use of low-intensity FUS, given in pulsed mode with 50% duty cycle (0.5 W/cm2 ISPTA) did not affect the bath temperature, demonstrating non-thermal unbinding of cisplatin.

In the following animal experiment, despite the use of lower intensity FUS (25% duty cycle, 345 kPa (MI of 0.8, ISPTA of 1 W/cm2) than that used in the in vitro experiment, sonication of the tumor (i.e., Cis+/Us+ condition) dramatically reduced its estimated size compared to the condition that involved the injection of cisplatin alone. Without the injection of cisplatin (in Cis− conditions), the tumor grew aggressively over a 12-day period. The volume and weight of the extracted tumor supports this observation. The skin temperature in the Us+ groups was not affected by sonication, suggesting that the observed tumor reduction occurred without thermal effects. The cisplatin-treated groups showed moderately reduced body weights, which we conjecture was due to the loss of appetite associated with the enhanced effects of cisplatin beyond the sonicated tumor location. The shape of the focus, an elongated ellipsoid, may have sonicated the tissue beyond the depth of the tumor, and affected the healthy tissue underneath. If this conjecture holds, the use of a higher frequency (e.g., ~1 MHz) and an alternative transducer geometry to yield a tighter focal shape would be required to isolate the effects of FUS only to the tumor.

These pilot data suggest that the presented FUS technique provides an elegant option for the much-needed, localized enhancement of cisplatin delivery. For later human applications, we envision transvaginal or peritoneal FUS application during the peak serum level of cisplatin (within ~1 h after administration) for treating advanced-stage cancer, as FUS can be administered on demand depending on the individual dosing schedule. This mitigates the risk of negative side effects without increasing the systemic dose. Alternatively, a reduced dose can be used to provide the same level of chemotherapeutic efficacy at the targeted tumor location in patients with a low systemic tolerance to cisplatin. The presented technique may also be applied to promote targeted delivery of other widely used chemotherapeutic agents with high binding affinity to plasma proteins with a narrow envelope of therapeutic doses (e.g., taxane-based agents, vinblastine, and tamoxifen, all having binding rates > 90%) (1).

Despite this promising prospect, the present pilot study had several limitations. First, intratumoral and systemic concentrations of cisplatin were not measured. This was necessary to gauge the in vivo effect of FUS in enhancing the localized delivery of cisplatin to the tumor. The unbinding would occur locally only during sonication (the unbinding is rapidly reversible) and would enhance the tumoricidal effects of unmodified cisplatin through increased regional uptake to the tumor. Liquid-liquid extraction of the intratumoral cisplatin combined with the measurement of the peripheral concentration of cisplatin are needed.

Furthermore, because the pulsing scheme affects the degree of unbinding and drug transport to the target tumor, the optimal sonication parameters that maximally unbind cisplatin at the lowest intensity are unknown and warrant further investigation. The search for an optimal acoustic parameter that yields maximal unbinding of cisplatin-albumin at the lowest possible intensity is also important to exclude the confounding effects of local temperature rise, which is known to affect pharmacokinetics, and to minimize risks of damage outside of the tumor margin. Sonication in an in vitro model of cervical cancer cultured on acoustically transparent membrane inserts would expedite the identification of the optimal sonication parameters. The in vitro tumor model will enable quantification of cisplatin uptake (accounting for active cellular drug transport and cell membrane permeability) that cannot be studied through in vitro equilibrium dialysis alone, providing more biologically relevant information.

We also acknowledge that the xenografted tumor in this pilot study was located subcutaneously and limited the evaluation of the effect of FUS on sonicating deep tumor tissue in a controllable manner. Further studies are required to investigate the effect of the technique on orthotopic implantation of ovarian or pancreatic cancer cells. In this case, image guidance, for example, based on bioluminescence imaging (BLI) of fluorescence-labeled cancer cell lines, is required to engage the targeted tumor. In addition to these limitations, we noted that biological effects of FUS, in the absence of cisplatin, on non-cancerous tissue in vicinity of the sonicated tumor, including effects on vascular permeability, tissue/vascular damage, metastasis, and animal behavior, warrant evaluations. Similar evaluations among non-tumor bearing mice that do not receive cisplatin are also desired to assess the isolated effects of sonication in the absence of cisplatin or its impact on metastatic activity.

Conclusion

Our findings highlight the feasibility of using FUS to unbind cisplatin from plasma protein and consequently enhance its tumoricidal effects on xenografted human cancer in mice. Further evaluation is required to determine whether the effects are directly linked to the localized unbinding and selective increase of cisplatin uptake into the tumor, without altering its systemic blood concentration.

Footnotes

  • Authors’ Contributions

    Yoo S-S., Katsarakes P, Gashi J, and Böhlke M conceived and designed the experiments. Yoo S-S., Katsarakes P, Gashi J, Kim E, and Böhlke M performed the experiment and collected the data. Yoo S-S., Katsarakes P, Gashi J, Kim HC, Kim E, and Kim HC analyzed the data. Yoo S-S., Katsarakes P, Gashi J, Kim HC, Kim E, and Kim HC drafted and edited the paper. Böhlke M reviewed and edited the paper.

  • Conflicts of Interest

    The Authors have no conflicts of interest to declare in relation to this study.

  • Received September 14, 2023.
  • Revision received October 9, 2023.
  • Accepted October 10, 2023.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).

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Non-thermal Acoustic Enhancement of Chemotherapeutic Effects of Cisplatin on Xenografted Cervical Cancer in Mice
SEUNG-SCHIK YOO, PERRY KATSARAKES, JASON GASHI, EVGENII KIM, HYUN-CHUL KIM, MARK BÖHLKE
Anticancer Research Nov 2023, 43 (11) 4793-4800; DOI: 10.21873/anticanres.16676
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