Abstract P4-09-18: Characterization of circulating myeloid derived suppressor cells and cytokines in patients undergoing neo-adjuvant chemotherapy for breast cancer

The Sweet Surrender: How Myeloid Cell Metabolic Plasticity Shapes the Tumor Microenvironment

Immune cells are one of the most versatile cell types, as they can tailor their metabolic activity according to their required function. In response to diverse environmental cues, immune cells undergo metabolic reprogramming to support their differentiation, proliferation and pro-inflammatory effector functions. To meet a dramatic surge in energetic demand, immune cells rewire their metabolism to utilize aerobic glycolysis. This preferential use of glycolysis even under aerobic conditions is well established in tumor cells, and is known as the "Warburg effect." Tumor cells avidly use glucose for aerobic glycolysis, thereby creating a nutrient-starved microenvironment, outcompeting T cells for glucose, and directly inhibiting T-cell anti-tumoral effector function. Given that both immune and tumor cells use similar modes of metabolism in the tumor stroma, it is imperative to identify a therapeutic window in which immune-cell and tumor-cell glycolysis can be specifically targeted. In this review, we focus on the Warburg metabolism as well as other metabolic pathways of myeloid cells, which comprise a notable niche in the tumor environment and promote the growth and metastasis of malignant tumors. We examine how differential immune-cell activation triggers metabolic fate, and detail how this forbidding microenvironment succeeds in shutting down the vigorous anti-tumoral response. Finally, we highlight emerging therapeutic concepts that aim to target immune-cell metabolism. Improving our understanding of immunometabolism and immune-cell commitment to specific metabolic fates will help identify alternative therapeutic approaches to battle this intractable disease.

Circulating myeloid-derived suppressor cells increase in patients undergoing neo-adjuvant chemotherapy for breast cancer

This study sought to evaluate whether myeloid-derived suppressor cells (MDSC) could be affected by chemotherapy and correlate with pathologic complete response (pCR) in breast cancer patients receiving neo-adjuvant chemotherapy. Peripheral blood levels of granulocytic (G-MDSC) and monocytic (M-MDSC) MDSC were measured by flow cytometry prior to cycle 1 and 2 of doxorubicin and cyclophosphamide and 1st and last administration of paclitaxel or paclitaxel/anti-HER2 therapy. Of 24 patients, 11, 6 and 7 patients were triple negative, HER2+ and hormone receptor+, respectively. 45.8% had pCR. Mean M-MDSC% were <1. Mean G-MDSC% and 95% confidence intervals were 0.88 (0.23-1.54), 5.07 (2.45-7.69), 9.32 (4.02-14.61) and 1.97 (0.53-3.41) at draws 1-4. The increase in G-MDSC by draw 3 was significant (p < 0.0001) in all breast cancer types. G-MDSC levels at the last draw were numerically lower in patients with pCR (1.15; 95% CI 0.14-2.16) versus patients with no pCR (2.71; 95% CI 0-5.47). There was no significant rise in G-MDSC from draw 1 to 3 in African American patients, and at draw 3 G-MDSC levels were significantly lower in African Americans versus Caucasians (p < 0.05). It was concluded that G-MDSC% increased during doxorubicin and cyclophosphamide therapy, but did not significantly differ between patients based on pathologic complete response.