Research Assistant USC Los Angeles, California, United States
Introduction: : Metastatic cancer cells are often softer than their non-invasive counterparts, which correlates with enhanced motility and immune evasion [1]. They also show higher sensitivity to external mechanical stimuli, such as ultrasound, manifesting in stronger intracellular calcium responses [2]. This suggests that, besides biochemical cues, the physical deformability of cancer cells may play a functional role in their mechanotransduction pathways. We propose that under identical acoustic pressures, softer cells experience greater deformation, which in turn amplifies calcium signaling. Our goal is to demonstrate that deformation magnitude can serve as a predictive proxy for calcium activity, enabling precise modulation of calcium-responsive gene activation. This study highlights a mechanistic link between cellular biomechanics and ultrasound-responsive gene modulation, advancing the paradigm of mechanical precision control in cancer treatment.
Materials and
Methods: : To finely tune cellular deformation and correlate it with real-time mechanotransduction, we built an integrated platform that couples ultrasound elastography with fluorescence microscopy. A focused-ultrasound transducer delivers mechanical stimulation to individual tumor spheroids, while a coaxial imaging array performs speckle-tracking elastography, generating micron-scale displacement maps. Simultaneously, an attached microscope records GCaMP fluorescence, providing a direct readout of ultrasound-evoked calcium influx. To allow mechanical input to be translated into programmable genetic output, cells are engineered with a calcium-responsive, doxycycline-gated AND-logic circuit (CaDox) that converts the calcium signal into expression of user-specified genes [3].
Results, Conclusions, and Discussions:: Initial tests in prostate-cancer PC-3 spheroids displayed a strong coupling between peak deformation and the integrated GCaMP calcium signal, establishing deformation as a quantitative predictor of mechanotransduction. The same trend emerged across two breast-cancer models with distinct biomechanical phenotypes. Metastatic, softer MDA-MB-231 spheroids consistently showed greater displacement and markedly stronger calcium transients than the stiffer, receptor-positive MCF-7 spheroids when exposed to identical ultrasound settings. Crucially, elevating the acoustic pressure on MCF-7 spheroids to match the deformation range seen in MDA-MB-231 largely erased the calcium gap between the two lines. This convergence suggests that, within the deformation range tested, calcium entry is largely dictated by the magnitude of mechanical strain rather than pre-existing molecular differences between the two lines. Leveraging the deformation window that maximized calcium contrast, we deployed the CaDox mechanogenetic circuit. Under these conditions, robust mCherry expression was triggered in MDA-MB-231 spheroids while remaining negligible in MCF-7 counterparts, demonstrating deformation-gated, cell-specific gene activation. Control groups lacking either doxycycline or ultrasound exhibited minimal fluorescence, confirming circuit specificity. Substituting mCherry with HSV-TK and adding ganciclovir under the same conditions selectively ablated MDA-MB-231 spheroids, whereas MCF-7 spheroids remained viable, demonstrating deformation-gated, cell-specific cytotoxicity. Our data highlight a new “mechanogenetic” approach for cancer cell modulation in which biomechanical phenotype, rather than molecular markers alone, guides therapy. The platform illustrates how focused ultrasound and strain sensing can be harnessed to target metastatic cancer cells while sparing stiffer, less invasive tissue counterparts. Future work will dissect the underlying ion-channel mechanisms and evaluate in vivo efficacy.
Acknowledgements and/or References (Optional):: [1] Swaminathan, V. et al. Mechanical stiffness grades metastatic potential in patient tumor cells and in cancer cell lines. Cancer Res. 71, 5075–5080 (2011) [2] J. Y. Hwang et al., Investigating contactless high frequency ultrasound microbeam stimulation for determination of invasion potential of breast cancer cells, Biotechnol. Bioeng. 110, 2697–2705 (2013) [3] C. W. Yoon et al., “Tumor Priming by Ultrasound Mechanogenetics for with SynNotch CAR T Therapy.” bioRxiv, (2024)
