Tumor Stroma Interactions: Wound Promoted Tumor Growth

Division Of Basic Sciences - Nci

Investigators

Abstract

The mechanisms of wound promoted tumorigenesis and tumor progression are not fully understood. In particular, the impact of an acute wound such as might occur during biopsy or explorative surgery on an existing tumor has not been addressed. Perhaps the greatest risk is the presence of unsuspected micro deposits of tumor left behind after tumor resection. Animal models to date have described the influence of preexisting wounds on tumor cells, or the influence of wounding on initiated hosts. For example, tumor incidence and tumor volume are higher if melanoma or fibrosarcoma cells are injected into a wound as compared to unwounded tissue, indicating that a preexisting wound microenvironment facilitates the establishment of tumors from a tumor cell inoculate. Likewise, the coinjection of wound fluid and melanoma cells resulted in increased tumor volumes. It has also been shown that full thickness transcutaneous wounding is a sufficient event for tumor expression and growth in both Rous-sarcoma virus infected chickens and v-ras transgenic mice. This demonstrates that wounding can promote tumorigenesis in a host that is already initiated by viral infection or by oncogene expression. In the Rous sarcoma chicken model TGF-beta, a pleiotropic cytokine, has been implicated as a molecular mechanism of wound initiated tumorigenesis. These reports suggest a strong similarity as well as interaction between the wound microenvironment and the tumor microenvironment, and that this interaction can accelerate tumorigenesis and tumor progression in an unfavorable way for the host. Clinically, surgical procedures are typically performed in the proximity of a pre-existing tumor as a necessary component of tumor treatment. While these procedures attempt to eradicate the tumor for the benefit of the patient, local tumor recurrence and implantation of tumor cells along the wound or the needle tract have been described. Although this is often attributed to mechanical tumor spread, the local wound environment itself may similarly influence any residual tumor cells in a negative way. Understanding the mechanisms involved in wound-tumor interactions will help to identify therapeutic targets to prevent a negative impact of such procedures on tumor patients. In order to understand the role of the immune system in wound promoted tumor growth we have begun to study how wounding influences tumor growth in immunocompromised animals. Using athymic BALB/c nu/nu mice we found that wounding does not significantly accelerate tumor growth, indicating that wound promoted tumor growth is mediated by T-cells. We furthermore could show that wound fluid not only increased proliferation rates in vitro, but also accelerated tumor growth in vivo when 4T1 cells were treated with wound fluid generated from BALB/c mice before injection into animals, or when wound fluid was injected in the proximity of the tumor site; wound fluid generated in BALB/c nu/nu animals had no significant effect on tumor cell proliferation or tumor growth. These data indicate that wound promoted tumor growth is relayed by a soluble factor secreted by T-lymphocytes. We currently aim to clarify the role of different T-cell subsets in our model, and started CD8 depletion experiments in collaboration with Lalage Wakefield. If applicable, we will use a similar approach to investigate other T-cell subsets such as CD4 cells by depletion. In parallel, we will harvest tumor tissue at different time points after wounding and analyze the influx of T-cell subsets into the tumor / wound microenvironment using immunohisochemistry and FACS analysis. Since we already demonstrated that wound fluid effects proliferation of tumor cells in vivo and tumor growth in vitro, we will analyze the cytokine expression pattern of wound fluid generated from BALB/c, BALB/c nu/nu mice, mouse plasma and mouse serum using antibody microarrays (Raybiotech); protein expression patterns will be analyzed by 2D-electrophoresis and subsequent mass-spectometry, and protein microarrays will be employed if applicable. Based on these approaches and the current literature, we will establish a shortlist of candidate cytokines or proteins that mediate wound promoted tumor growth. Alternatively, we will start fractionating wound fluid and investigate the effect of these fractions on tumor cells and stromal cells such as fibroblasts or endothelial cells in order to identify new effector molecules. Furthermore TGF-beta has been implicated in wound triggered tumorigenesis in Rous sarcoma virus infected chickens. TGF-beta's has a complex role in tumorigenesis and metastases, and its influence on different cells types depends on the cell type and the signaling context. For example, TGF-beta can stimulate matrix secretion by stromal cells and angiogenesis, and modulates immune function, all of which are altered during tumorigenesis as well as during wound healing. Using a Smad3 knockout model we could show that defect stromal TGF-beta signaling yields smaller tumors in the 4T1 model, and that tumors from Smad3 knockout animals have less CD31 positive vessels. We are currently breeding the Smad3 knockout into the BALB/c background to analyze the effect of defective stromal TGF-beta signaling on wound promoted tumor growth. Alternatively, we will neutralize TGF-beta systemically or in the tumor microenvironment by using a neutralizing antibody (1D11), and analyze the effect of wounding in these animals.