Targeting immune checkpoint

Tumor cell transformation prompts to activation of adaptive and innate immune responses, which had a crucial role in eliminating and controlling early cancer growth. Over the past 10 years, there has been a greater understanding of the immune response to tumors which has led to the development of a huge number of immunotherapeutic strategies [1, 2]. The immune system plays a dual role in cancer: it not only can suppress tumor growth by destroying cancer cells or inhibiting their outgrowth but also promotes tumor progression either by selecting for tumor cells that are more fit to survive in an immunocompetent host or by establishing conditions within the tumor microenvironment that facilitate tumor outgrowth. The conceptual framework called “cancer immunoediting” integrates the immune system’s dual host-protective and tumor-promoting roles. Nonetheless, numerous studies have shown that tumors can be recognized and contained for extended periods of time by the immune response through the concerted action of the innate and adaptive immune responses [3]. Agents such as the immune checkpoint inhibitors have demonstrated to induce a response in a number of solid malignancies [4], but their therapeutic benefit has not been seen in all cancer types. The initial enthusiasm for immune checkpoint inhibitors is mainly based on results obtained in melanoma, lung cancer, bladder cancer, and renal cell carcinoma [5]. But also in breast cancer (BC), preliminary data from the first clinical studies is encouraging.