Model development using malignant pleural effusions for extracting and validating lung cancer stem cells.
Objective: Our overall objective is to sort cancer stem cells (CSC) from an advanced model of lung cancer in order to better treat this disease. Once CSC are identified, they will be used to develop immune based treatments for lung cancer, and their distinctive properties will be exploited to design new drug treatments for lung cancer.
Approach: Current research primarily seeks to identify genes and gene expression profiles to determine commonalities amongst different subtypes of lung cancer for diagnostic and prognostic purposes. The hope is that such analyses will provide the doctor with tools to “personalize” a treatment approach. Given the high mortality attributable to lung cancer, this is an important undertaking. However, we feel that these approaches are likely to fall short because they discount the known fact that even individual lung cancers have significant variability. Thus, targeting a single molecular abnormality to treat patients with lung cancer may be misguided.
In contrast, our approach is unique and revolutionary. Whereas others look to minimize or exclude intratumoral heterogeneity, we have chosen to focus on it. We believe that developing therapies based on oversimplified models of lung cancer has not, and will not result in significant treatment advances. Thus, in 2006, we began to develop a model to examine the cell-variability in clinical lung cancer specimens. One possibility why there is variability amongst cancer cells from an individual patient is that the tumor may in fact be derived from a small fraction of progenitor or cancer stem cells (CSC). To determine if this is the case, we elected to look for CSC in clinical lung cancer specimens. We have identified cells that express candidate lung CSC-markers, and have developed the ability to keep them alive in cultures. Now, we want to sort out these candidate CSC, and determine whether they exhibit properties of cancer stem cells.
Bottleneck: We hope to further develop and refine methods to select CSC from lung cancer specimens, in an overall effort to use these CSC as the target in vaccination strategies to treat lung cancer. The key obstacles to that goal are 1) extract and characterize lung CSC, and 2) reproduce the advanced human lung cancer in an animal model to test the effectiveness of vaccination (or other treatment strategies) in a relevant environment. Because we intend to use patient-derived tumor and immune cells, we will need to develop a special mouse model, which can house human tissues, for this purpose. Our goal is to begin to overcome these obstacles over the next three years.
Lung cancer will be diagnosed in approximately 18,000 Californians this year. Of these, over 15,300 individuals can be expected to die within the next 5 years; the majority within two years from the time of diagnosis. The ineffectiveness of treatment for lung cancer, we feel, is in part accounted for by how we have chosen to study and develop strategies to treat this disease. Although we have long recognized that all the lung cancer cells in patients with lung cancer are not alike (ie: there are heterogeneous subpopulations of cancer cells), the models that have been used to determine the effectiveness of treatment strategies have been simplified to target cells which are similar in their characteristics. For the large part, treatments have sought to kill off rapidly dividing cells, but that approach leaves behind tumor cells that are not rapidly dividing, or those which are inherently resistant to such anti-cancer drugs. We believe that to develop successful treatment strategies for lung cancer, we have to both recognize and model lung cancer in an appropriately complex disease model. Over the long term, we seek to develop such a model; one that is fully capable of recapitulating the biological heterogeneity that is evident in clinical disease.
One mechanism by which there may be biological heterogeneity in lung cancer is that the tumor originates in cancer stem cells (CSC). These CSC, in turn give rise to a large number of daughter cells that possess distinctive properties from the CSC. It is also very likely that various daughter cell subpopulations evolve distinctly from each other over the lifespan of the tumor. It has been proposed by others that if we can identify the original CSC in tumors, then developing treatment approaches based on selectively killing will lead to better survival, or even cures from cancer.
No one has previously attempted to isolate lung CSC from clinical specimens. Using specimens that are derived from lung cancer patients with advanced disease, we have been able to identify cells that display features of CSC. Presently, we want to refine our ability to isolate and study these potential lung CSC, and to develop a new model which will be used to make sure that the cells we have isolated are bona fide lung CSC, and which will be further developed to mimic more precisely the human disease. This model will allow us to test experimental treatment strategies in an appropriately complex disease model. If successful, this approach will be used to develop treatment strategies to prolong the life of those 18,000 Californians who are newly diagnosed with lung cancer every year, or possibly even cure them.