Light Scattering Measurements of Subcellular Structure Provide Noninvasive Early Detection of Chemotherapy-induced Apoptosis

摘要

We present a light scattering study using angle-resolved low coherence interferometry (a/LCI) to assess nuclear morphology and sub-cellular structure within MCF-7 cells at several timepoints following treatment with chemotherapeutic agents. While the nuclear diameter and eccentricity are not observed to change, the light scattering signal reveals a change in the organization of sub-cellular structures that we interpret using fractal dimension (FD). The FD of sub-cellular structures in cells treated with paclitaxel and doxorubicin is observed to increase significantly compared to that of control cells as early as 1.5 and 3 hrs after application, respectively. The FD is then found to decrease slightly at 6 hrs post application for both agents only to increase again from 12 to 24 hrs post treatment when the observations ceased. The changes in structure appear over two time scales, suggesting that multiple mechanisms are evident in these early apoptotic stages. Indeed, quantitative image analysis of fluorescence micrographs of cells undergoing apoptosis verify that the FD of DAPI stained nuclear structures does not change significantly in cells until 12 hrs after treatment while that of MitoTracker stained mitochondria is seen to modulate as early as 3 hrs after treatment. In contrast, cells receiving an increased dose of paclitaxel that induced G2/M arrest, but not apoptosis, only exhibited the early change in sub-cellular structure but did not show the later change associated with changes in nuclear substructure. These results suggest the a/LCI may have utility in detecting early apoptotic events for both clinical and basic science applications.