In Vitro invasive pattern of hepatocellular carcinoma cell line HCCLM9 based on three-dimensional cell culture and quantum dots molecular imaging

Abstract

This study aimed to establish a new in vitro three-dimensional (3D) cell culture and use quantum dots (QDs) molecular imaging to examine the invasive behaviors of hepatocellular carcinoma (HCC) cells. Each well of the 24-well cell culture plate was cover-slipped. Matrigel diluted with serum-free DMEM was added and HCCLM9 cells were cultured on the Matrigel. The cell morphological and cell growth characteristics were observed by inverted microscopy and laser confocal microscopy at different culture time. Cell invasive features were monitored by QDs-based real-time molecular imaging techniques. The results showed that on this 3D cell culture platform, HCCLM9 cells exhibited typical multi-step invasive behaviors, including reversion of cell senescence, active focal proliferation and dominant clones invasion. During the process, cells under 3D cell culture showed biological behaviors of spatio-temporal characteristics. Cells first merged on the surface of matrix, then gradually infiltrated and migrated into deep part of matrix, presenting polygonal morphology with stretched protrusions, forming tubular, annular and even network structure, which suggested that HCC cells have the morphological basis for vasculogenic mimicry. In addition, small cell clones with their edges well-circumscribed in early stage, progressed into a large irregular clone with ill-defined edge, while the other cells developed invadopodia. And QDs probing showed MT1-MMP was strongly expressed in the invadopodia. These findings indicate that a novel 3D cell culture platform has been successfully established, which can mimic the in vivo tumor microenvironment, and when combined with QDs-based molecular imaging, it can help to better investigate the invasive behaviors of HCC cells.