Abstract 1554: Myeloid derived suppressor cells-mediated inflammation in metastasis and cancer cachexia
Authors: Ouzounova Maria , Lee EunMi , Piranlioglu Raziye , Novakovic Ena , Demirci Mehmet , Korkaya Sumeyye , Hudson Alicia , Korkaya Hasan 
Published: July 2016

Despite recent advances and better diagnostics, the major challenge is that metastatic breast cancer is still incurable and remains leading cause of cancer related death. Cachexia is considered to be a chronic inflammatory syndrome which is defined by loss of skeletal muscle mass (with or without loss of adipose mass), negative energy and metabolic balance, and systemic inflammation. Cancer patients who develop cachexia are more susceptible to infections and sepsis. Clinical studies suggest that cachexia in cancer patients cannot be fully reversed by conventional nutritional supports, which distinguishes this condition from anorexia. Due to its complexity and lack of clinical biomarkers, currently there is no standard treatment for these patients. Therefore cachexia remains a largely underestimated and untreated condition. Nearly 60-80% of the advanced/ metastatic cancer patients experience cachexia, a condition that accounts for 20% of cancer-related deaths.

Chronic inflammation has been recognized as a risk factor contributing to the etiology of many human malignancies. Accumulating evidence suggest that tumor infiltrating immune cells (mainly myeloid origin) differentiate into cells that promote tumor growth and metastasis via inducing a systemic inflammation. Our preliminary studies suggest that systemic induction and infiltration (tumor, bone marrow, spleen, liver, and lung) of myeloid derived suppressor cells (MDSC) generate a pro-inflammatory micro-environment and are a major source of inflammatory cytokines, many of which are implicated in cancer cachexia. Using a murine breast cancer in a syngeneic (immunocompetent) mouse model we show that metastatic (4T1) murine tumor produce significantly higher level of inflammatory cytokines and is able to induce systemic expansion and infiltration of MDSC compared to non-metastatic murine tumor (EMT6). Furthermore, injection of condition media from metastatic 4T1 tumor cells is also able to induce MDSC expansion in vivo suggesting that tumor-produced factors play role in this process. Moreover, we demonstrate the involvement of the inflammatory cytokines in muscle wasting as shown by co-culture experiments with C2C12 myoepithelial cells and analysed the expression of cachexia markers such as E3 ubiquitin ligases Trim63 and Fbxo3, Myh1(myosin heavy chain), Stat3 and NFkB pathway activation, and elevation of pro-cachexia cytokines.

Our preliminary studies demonstrated that the monocytic MDSC induce EMT phenotype and contribute to the dissemination of tumor cells while the granulocytic MDSC promote the metastatic outgrowth, and present higher infiltration in the lungs. We therefore propose that tumor-induced inflammatory cytokines play role in induction of MDSC and further elevation of inflammatory markers leading to metastasis and cancer cachexia.

Citation Format: Maria Ouzounova, EunMi Lee, Raziye Piranlioglu, Ena Novakovic, Mehmet Demirci, Sumeyye Korkaya, Alicia Hudson, Hasan Korkaya. Myeloid derived suppressor cells-mediated inflammation in metastasis and cancer cachexia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1554.