title: Investigating contactless high frequency ultrasound microbeam stimulation for determination of invasion potential of breast cancer cells.
abstract: In this article, we investigate the application of contactless high frequency ultrasound microbeam stimulation (HFUMS) for determining the invasion potential of breast cancer cells. In breast cancer patients, the finding of tumor metastasis significantly worsens the clinical prognosis. Thus, early determination of the potential of a tumor for invasion and metastasis would significantly impact decisions about aggressiveness of cancer treatment. Recent work suggests that invasive breast cancer cells (MDA-MB-231), but not weakly invasive breast cancer cells (MCF-7, SKBR3, and BT-474), display a number of neuronal characteristics, including expression of voltage-gated sodium channels. Since sodium channels are often co-expressed with calcium channels, this prompted us to test whether single-cell stimulation by a highly focused ultrasound microbeam would trigger Ca(2+) elevation, especially in highly invasive breast cancer cells. To calibrate the diameter of the microbeam ultrasound produced by a 200-MHz single element LiNbO3 transducer, we focused the beam on a wire target and performed a pulse-echo test. The width of the beam was ∼17 µm, appropriate for single cell stimulation. Membrane-permeant fluorescent Ca(2+) indicators were utilized to monitor Ca(2+) changes in the cells due to HFUMS. The cell response index (CRI), which is a composite parameter reflecting both Ca(2+) elevation and the fraction of responding cells elicited by HFUMS, was much greater in highly invasive breast cancer cells than in the weakly invasive breast cancer cells. The CRI of MDA-MB-231 cells depended on peak-to-peak amplitude of the voltage driving the transducer. These results suggest that HFUMS may serve as a novel tool to determine the invasion potential of breast cancer cells, and with further refinement may offer a rapid test for invasiveness of tumor biopsies in situ.
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Jae Youn
authors.initials: JY
authors.lastname: Hwang
authors.forename: Nan Sook
authors.initials: NS
authors.lastname: Lee
authors.forename: Changyang
authors.initials: C
authors.lastname: Lee
authors.forename: Kwok Ho
authors.initials: KH
authors.lastname: Lam
authors.forename: Hyung Ham
authors.initials: HH
authors.lastname: Kim
authors.forename: Jonghye
authors.initials: J
authors.lastname: Woo
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Lin
authors.forename: Kassandra
authors.initials: K
authors.lastname: Kisler
authors.forename: Hojong
authors.initials: H
authors.lastname: Choi
authors.forename: Qifa
authors.initials: Q
authors.lastname: Zhou
authors.forename: Robert H
authors.initials: RH
authors.lastname: Chow
authors.forename: K Kirk
authors.initials: KK
authors.lastname: Shung
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D006801:Humans; D042541:Intracellular Space / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D009361:Neoplasm Invasiveness; D061848:Optical Imaging / Q000379:methods*; D017239:Paclitaxel / Q000494:pharmacology; D013016:Sound
chemical_list: D000970:Antineoplastic Agents; D017239:Paclitaxel; D002118:Calcium
keywords: calcium fluorescence imaging; cell stimulation; high frequency ultrasound microbeam; invasiveness, breast cancer cells; live-cell imaging; mechanotransduction