When Ajay Tijore was a postdoctoral researcher in mechanobiologist Michael Sheetz’s lab at the National University of Singapore, he and his team studied how mechanical strain affected cancer cells. A few years ago, the researchers found that low-frequency ultrasound waves triggered mechanical stress that killed several invasive cancer cell types.1 “That was kind of a big revelation…[a] Eureka moment,” said Tijore.
When he started his own lab at the Indian Institute of Science in 2021, Tijore hoped to contribute to Indian society. With India accounting for one-third of the oral cancer cases worldwide, Tijore sought to investigate whether low-frequency ultrasound could also target oral cancer cells.2
Study coauthors Rashmita Luha and Ajay Tijore tested the potential of low-frequency ultrasound to selectively kill patient-derived oral cancer cells.
Siddhesh Saiganonkar, Indian Institute of Science
Now, Tijore and his team found that patient-derived oral cancer cells are susceptible to low-frequency ultrasound due to their distinct biomechanical properties compared to healthy cells.3 The team’s findings, published in Materials Today Bio, highlight the potential of the non-invasive approach in oral cancer therapy.
“[This] is a good paper [with] in vitro data,” said Anutosh Ganguly, whose research at the University of Michigan involves ultrasound-mediated tumor ablation and was not involved with the study. “It raises more questions to be answered, but it is the first step.”
Ultrasound Disrupts Oral Cancer Cell Migration
Tijore and his team began by isolating oral cancer cells from patient-derived tumor samples. They then subjected the cells to low-frequency ultrasound using a custom-made device.4 The frequency of this type of ultrasound is about 40 kilohertz, while the frequency of ultrasound routinely used in clinics for diagnostic scans ranges from two to 18 megahertz.
While this did not affect healthy control cells, ultrasound mechano-stimulation inhibited the spreading of the cancer cells. To investigate the molecular mechanism underlying this, the researchers examined the cells’ focal adhesions. These multi-protein complexes physically link the cell’s cytoskeleton to its extracellular matrix and promote cell spreading. They observed that ultrasound reduced focal adhesion proteins, indicating that it potentially reduces cancer cell spreading by disassembling focal adhesions.
Tijore and his team also assessed the effect of ultrasound on cancer cell migration using in vitro assays. Compared to untreated cells, ultrasound-treated cells showed reduced cell migration. Treated cells also showed less invasion capacity compared to untreated cells when placed in collagen, suggesting that ultrasound suppresses cancer cell migration and invasion.
Next, the researchers sought to understand the properties underlying why ultrasound specifically resulted in cancer cell apoptosis. Researchers have previously shown that depletion of tropomyosin 2.1 (Tmp2.1), a mechanosensory protein that regulates traction forces in cells, makes them vulnerable to ultrasound-mediated apoptosis, or mechanoptosis.5
Immunofluorescence and immunoblotting revealed that oral cancer cells expressed less Tmp2.1 compared to control cells, suggesting that Tpm2.1 depletion in oral cancer cells could render them mechanically vulnerable.
Loosening the Tumor Barrier Could Enhance Chemotherapy Efficacy
Finally, Tijore and his team investigated the translational applications of their findings. Patients with oral cancer often exhibit stiffness around their tumor, said Tijore, which forms due to cancer cells recruiting fibroblasts to themselves. These cancer-associated fibroblasts envelope the tumor core, acting as a barrier that prevents chemotherapeutic drugs or immunotherapeutic cells from infiltrating the tumor, which drives resistance to therapies.
Fluorescence microscopy revealed that ultrasound treatment reduced cancer-associated fibroblasts (magenta) cocultured with patient-derived oral cancer cells (green).
Rashmita Luha, Indian Institute of Science
Consistent with this, the researchers observed cancer-associated fibroblasts blanketing tumor cells upon visualizing patient-derived tumor samples using immunohistochemistry. To mimic this tumor microenvironment in vitro, Tijore and his team cocultured patient-derived tumor cells with cancer-associated fibroblasts. They found that ultrasound reduced the infiltration of cancer-associated fibroblasts, exposed the tumor core, and highlighted that ultrasound mechano-stimulation could loosen the barrier enveloping the tumor to enhance drug permeability.
This was “striking,” said Tijore, because this finding indicated that ultrasound could potentially help improve the effectiveness of existing therapies.
According to Ganguly, the focal adhesion dynamics that the researchers uncovered are interesting. “This is a good first start,” he said. However, he noted that although the results reveal that loss of Tmp2.1 renders the cells vulnerable to ultrasound-mediated death, the exact cell death pathway remains unclear.
While researchers can study this process in vitro, the “future work is [to see] how we can make this translational,” said Ganguly. The next step would be to conduct experiments in vivo, he explained.
Studying the effect of ultrasound on patient-derived oral cancer organoids or animal models would come next, agreed Tijore. “We have already gotten ethical approval from the institute to perform animal studies,” he added.
Looking back, Tijore said that the most satisfying aspect of working on this project was receiving emails and phone calls from patients and hospitals volunteering to participate in clinical studies after reading the paper. This has motivated the team to work harder to get a clearer picture of the efficacy and safety of ultrasound mechano-stimulation in vivo. “The most exciting [part] is that when as a researcher, you find that some discovery or some technology [that] you are developing is going to help society,” said Tijore.
- Singh A, et al. Enhanced tumor cell killing by ultrasound after microtubule depolymerization. Bioeng Transl Med. 2021;6(3):e10233.
- Sathishkumar K, et al. Geographic disparities in oral cancer survival from 10 population-based cancer registries in India. JAMA Netw Open. 2025;8(4):e253910.
- Luha R, et al. Revealing biomechanical vulnerabilities in oral cancer cells using 3D coculture platform and low-frequency ultrasound. Mater Today Bio. 2026;39:103375.
- Veena SM, et al. Nanoscale ligand spacing regulates mechanical force-induced cancer cell killing. Nano Lett. 2025;25(6):2418-2425.
- Yang B, et al. Stopping transformed cancer cell growth by rigidity sensing. Nat Mater. 2020;19(2):239-250.
