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2012 LCRP Investigator Vignette

Title: Development of an in Vitro Three-Dimensional Cell Culture Model of Clinically Relevant Human Lung Cancer

Investigator: Anirban Datta, PhD; University of California, San Francisco

The objective of my DoD-funded research was to develop clinically relevant models of lung adenocarcinoma, which is the largest subgroup of lung cancer. I have used a 3-dimensional cell culture model to create an in vitro model of how lung cancers develop in vivo.

This is a lung adenocarcinoma. What you notice right away is that these lung cancer cells have formed circular balls of cells and this with this white area inside that are fluid-filled spheres. And this is typically the architecture of lung adenocarcinomas in that they actually form these polarized balls of cells. And the main reason why we're interested in this is that formation of these polarized spherical architecture is associated with resistance to traditional chemotherapy drugs.

We don't know whether the structure imparts resistance or the resistance leads to some sort of changes in the cell that leads to the structure. But we know that it's somehow causally linked. And also understanding of the molecular pathway we hope will help us target specific drugs against this pathway so that maybe we can actually prevent resistance to chemotherapy.

So what we do is we actually embed these lung adenocarcinomas in a 3-dimensional cell culture, which is depicted here in a cartoon form. These cells sit down in these little chambers, the bottom of which is covered by 100% layer of what we call basement membrane which is a meshwork of protein isolated from a different tumor; and we put a smaller layer, a 2% layer in fact, of this base membrane component with the cells inside this dish. Over the next 5 to 9 days they grow up in these beautifully round hollow ball of cells. Inside you you will see they are actually fluid-filled and outside are these circular or spherical balls of cells.

The challenge for us was that cancer cells lines, the majority of them, they in fact do not form the beautiful architecture that you saw in the biopsy so the "a-ha" moment that came was when I realized that other factors from the tumor was required for these tumor cells to go from a solid ball into a what we call a polarized acini. And in fact I have identified the growth factor that's required to grow from this amorphous mass to this polarized ball of cells.

Using this system we are actually currently dissecting the molecular pathway that's involved in going from here to here. And also, then this was the other part of my DoD-funded research, I have expressed some of the most common gene mutations in lung cancer; namely, activated KRAS, EGFR, and a few of the other ones et cetera, and there's a key difference between when we express the KRAS oncogene activated form versus the EGFR oncogene in that KRAS oncogene does not disrupt the architecture, whereas EGFR oncogene does disrupt the architecture. In a somewhat paradoxical way that suggests a possible mechanism as to why KRAS-induced lung cancer has become resistant to chemotherapy frequently because KRAS still maintains the architecture allowing them to develop resistance more readily.

Currently, I'm in the process of establishing some collaborations with other investigators asking one whether the genes I've identified in this pathway are actually disrupted in lung cancer and number two whether I can look at animal models of lung cancer and identify any disruption of these genes also.