|M.Sc Student||Davidi Shiri|
|Subject||The Role of IL-31 in Tumorigenesis|
|Department||Department of Medicine||Supervisors||Professor Yuval Shaked|
|Professor Ami Aronheim|
Developing new drugs against cancer is a great challenge. While most drugs target tumor cells, studies suggest that inhibition of pro-tumor adjacent cells provides a useful strategy to inhibit tumor growth. The tumor microenvironment plays a crucial role in tumor growth and metastasis, therefore identifying host derived cells and factors with either proangiogenic or protumorigenic activity could potentially be used as a new strategy to target cancer. To identify potential target molecules, we screened for up-regulated host factors in plasma following chemotherapy and identified Interleukin 31 (IL-31), a pro-inflammatory cytokine that leads to dermatitis. Currently, the role of IL-31 in tumorigenesis is unknown.
Here we show that IL-31 is highly expressed in various human and mouse tumor cell lines. Moreover, the expression of IL-31 receptor can be found in tumor tissue / biopsy of human colorectal and breast carcinoma. To explore the anti-tumor activity of IL-31 in vivo, we implanted colorectal cells (MC38) and breast carcinomas (4T1) in mice. We detected remarkable tumor growth retardation, reduced angiogenesis and lower metastases spread in the IL-31 treated groups.
Since IL-31 has a short half-life in the circulation, we generated a stable IL-31 protein, using chimeric IL-31 proteins fused to the FC fragment of IgG (IL-31-IgG). The protein was fused to His-tag for purification and Myc-Tag for detection. The stability of purified protein was evaluated in mice, IL-31 was completely unstable and the FC-IgG fused protein was detected in the blood with a half-life of 72h. The activities of the purified proteins were evaluated using a reporter based assay, based on IL-31 signaling pathway that activates STAT3 transcription factor. The purified human IL-31-IgG (hIL-31-IgG) was as active as the hIL-31 lacking IgG. Yet, while the purified mIL-31- displayed efficient activity, no significant activity was observed for mIL-31-IgG.
Next, to examine in vivo activity, we implanted HCT116, human colon cancer, into NOD-SCID mice. Tumor growth was inhibited significantly with reduced angiogenesis in the IL-31 treated group. To demonstrate that IL-31 treatment affected angiogenesis indirectly, HCT116 were cultured in the absence or presence of hIL-31. Conditioned medium was collected and applied onto HUVEC cells which were quantified for tube formation. Conditioned medium derived from cells treated with hIL-31 inhibited tube formation more significantly as compared to conditioned medium derived from untreated HCT116 cells. Therefore, IL-31 has an antiangiogenic activity by direct/indirect inhibition of angiogenesis.
Lastly, we show that hIL-31 has an additive therapeutic activity when given in combination with chemotherapy. We implanted LM2-4 human breast carcinoma cells to the mammary fat pad of NOD-SCID mice. PTX chemotherapy was given every fortnight while another group received a combined treatment with hIL-31-IgG. The combined therapy presented a prominent anti-tumor activity compared to PTX alone.
Our results demonstrate that IL-31 inhibits tumor growth, reduces angiogenesis and metastases spread. We suggest IL-31 as a multi-targeted agent that affects both tumor and host-derived protumorigenic cells. This study will pave the way toward the development of a novel anti-cancer modality affecting primary tumors and metastasis.