PURPOSE: The prognosis of patients with bronchiolo-alveolar carcinoma (BAC) containing actively proliferating fibroblasts is poor, with cancer cells invading frequently into micro-vessels. Cancer-stroma communication seems to be important for the development of the invasive component of BAC. We established an easy-to-prepare double-layered collagen gel hemisphere (DL-CGH) system for in-vitro invasion assay, and successfully visualized cancer-stroma interaction during invasion.
METHODS: Double-layered collagen gel hemisphere (DL-CGH) system consists of a central core collagen layer surrounded by an outer cover collagen layer. A droplet of collagen I solution (containing cells to be examined) naturally forms a small hemisphere on the bottom of the culture dish. After this central core layer gels, a second droplet is placed atop the first gel, encapsulating it completely. The hemisphere is submerged in the medium and cultured.
RESULTS: A549, bronchiolo-alveolar carcinoma (BAC), and WI-38, lung fibroblast, were mixed in the inner layer of the gel and watched with inverted microscope over time. Fibroblasts cut their way through the outer collagen gel, and the cancer cells run after the fibroblasts. Next, A549 and WI-38 were separately embedded in inner and outer layer, and we found the cancer cells running around outer layer along the network of fibroblasts. As a result, BAC cells, which could not infiltrate into outer layer by themselves, invaded with the help of fibroblast.
CONCLUSION: The observation that A549 cells embedded together with fibroblasts in 3-D gel hemispheres recovered mobility demonstrates clearly that this type of cancer cells require stromal cells for invasion. BAC cells, which lack the proteases required for direct entrance into the three-dimensional collagen matrix, were seen to slip like amoeba through matrix gaps generated by the pericellular proteolytic activity of fibroblasts.
CLINICAL IMPLICATIONS: These findings were consistent with some clinical reports concerning of cancer-stroma interaction for invasion in BAC with invasive components. Further investigations into intercellular communication should help clarify the molecular mechanisms of cancer invasion at work of the tumor-host interface and establish the new strategy for control of cancer invasion.
DISCLOSURE: Yoshimasa Maniwa, No Financial Disclosure Information; No Product/Research Disclosure Information