Melanoma remains a challenge in clinical oncology. Evidence increasingly suggests that inflammation can be associated with unfavorable clinical prognosis in cancer patients. IL-1b is a pleiotropic pro-inflammatory cytokine and induces a broad portfolio of genes from many cells. We have shown that metastatic melanoma cells spontaneously secrete biologically active IL-1b in the absence of exogenous stimuli because of constitutive activation of IL-1 receptor (IL-1R) signaling and a multi-protein complex, "inflammasome", exhibiting a feature of "auto-inflammation". We hypothesize that auto-inflammation from melanoma cells contributes to tumor growth and progression in tumor microenvironment. We propose to unravel the molecular (in Aim 1) and biological (in Aim 2) mechanisms of auto-inflammation in human melanoma cells.
In Aim 3, we will investigate if auto-inflammation is associated with a subpopulation of melanoma cells such as cancer stem cells (CSCs).
The specific aims are:
Specific Aim 1. To analyze molecular mechanisms regulating auto-inflammation in human melanoma. We will delineate molecular mechanisms of auto-inflammation by assessing the role of inflammasomes in Aim 1.1. ASC, NLRP1 and NLRP3 will be silenced from human metastatic melanoma cell lines with short hairpin RNA and its role on molecular signaling and biological function will be assessed. We will then examine inflammasome-independent pathway in Aim 1.2.
Specific Aim 2. To examine the biological role of auto-inflammation in tumor microenvironment. We will utilize a direct patient tumor xenograft model by implanting human melanoma tissues directly into mice in Aim 2.1. This is one of the best models in human cancer research that recapitulate complex tumor microenvironment. In addition, a genetically engineered mouse model (GEMM) of melanoma will be used in Aim 2.2 to better address tumor biology in immunocompetent syngeneic mice. We will examine the role of melanoma-derived IL-1b and auto-inflammation on survival of melanoma cells and recruiting and activating stromal cells in tumor microenvironment.
Specific Aim 3. To assess if auto-inflammation is associated with a subpopulation of melanoma cells such as CSCs. We reported heterogeneous IL-1b expression in metastatic melanoma tumors. The CSC hypothesis proposes that a subpopulation of tumor cells is responsible for survival and maintaining of the growth of neoplastic tissue. Recently, we identified a subpopulation of human melanoma cells that possess CSC properties and express high aldehyde dehydrogenase (ALDH) activity. These cells express unique genes and IL-1 signaling network, suggesting that melanoma auto-inflammation may be associated with CSCs. We will measure IL-1b production and secretion from 4 potential CSCs and non-CSCs (Aim 3.1) and assess autoinflammatory nature of CSCs on non-CSCs by co-culturing these populations in Aim 3.2. The subpopulation that shows auto-inflammation will be further analyzed phenotypically and biologically in Aim 3.3. Both human tumors and GEMM tumors will be used. Until now, little has been studied on the mechanisms and roles of inflammasome and auto-inflammation from non-immunological cells such as tumor cells. Since IL-1b plays an important role in cancer biology, elucidating biological mechanisms of auto-inflammation in cancer will help our understanding of tumor initiation, progression and recurrence and is critical for a successful treatment against melanoma. It will also lead to the discovery of novel molecular targets for cancer drug development.
Sun exposure is part of the daily life for U.S. troops, especially during summer. The risk of developing melanoma doubles if an individual is exposed to acute sunburn at an early age or >5 sunburns at any age. Sun exposure during US military service has also been linked to increased melanoma incidence. Furthermore, melanoma is more common than other cancers in young women, an increasingly significant population in the VA and in the active-duty military. Thus, understanding mechanisms responsible for melanoma initiation and progression in the tumor microenvironment is critical for the successful prevention and effective treatment of melanoma for VA patients. We found that human melanoma cells exhibit a feature of autoinflammation. The link between cancer and inflammation is well known. We will study the mechanisms of autoinflammation in human melanoma. Furthermore, we will ask whether a subpopulation of tumor cells, called cancer stem cells, may be associated with the autoinflammation in human melanoma.