Current status and future prospective of breast cancer immunotherapy.

The immune system is complicated, interconnected, and offers a powerful defense system that protects its host from foreign pathogens. Immunotherapy involves boosting the immune system to kill cancer cells, and nowadays, is a major emerging treatment for cancer. With the advances in our understanding of the immunology of cancer, there has been an explosion of studies to develop and evaluate therapies that engage the immune system in the fight against cancer. Nevertheless, conventional therapies have been effective in reducing tumor burden and prolonging patient life, but the overall efficacy of these treatment regimens has been somewhat mixed and often with severe side effects. A common reason for this is the activation of molecular mechanisms that lead to apoptosis of anti-tumor effector cells. The competency to block tumor escape entirely depends on our understanding of the cellular and molecular pathways which operate in the tumor microenvironment. Numerous strategies have been developed for activating the immune system to kill tumor cells. Breast cancer is one of the major causes of cancer death in women, and is characterized by complex molecular and cellular events that closely intertwine with the host immune system. In this regard, predictive biomarkers of immunotherapy, use of nanotechnology, personalized cancer vaccines, antibodies to checkpoint inhibitors, engineered chimeric antigen receptor-T cells, and the combination with other therapeutic modalities have transformed cancer therapy and optimized the therapeutic effect. In this chapter, we will offer a holistic view of the different therapeutic modalities and recent advances in immunotherapy. Additionally, we will summarize the recent advances and future prospective of breast cancer immunotherapies, as a case study.

Regulatory lymphocytes: the dice that resolve the tumor endgame

A large number of cancer patients relapse after chemotherapeutic treatment. The immune system is capable of identifying and destroying cancer cells, so recent studies have highlighted the growing importance of using combinatorial chemotherapy and immunotherapy. However, many patients have innate or acquired resistance to immunotherapies. Long-term follow-up in a pooled meta-analysis exhibited long-term survival in approximately 20% of patients treated with immune checkpoint inhibitors or the adoptive transfer of chimeric T cells. It has been reported that high levels of immunoregulatory cells in cancer patients contribute to immunotherapy resistance via immunosuppression. Among the most important regulatory cell subtypes are the CD4+ T-regulatory cells (Tregs), identified by their expression of the well-characterized, lineage-specific transcription factor FOXP3. In addition to CD4+ Tregs, other regulatory cells present in the tumor microenvironment, namely CD8+ Tregs and IL10-producing B-regulatory cells (Bregs) that also modulate the immune response in solid and lymphoid tumors. These cells together have detrimental effects on tumor immune surveillance and anti-tumor immunity. Therefore, targeting these regulatory lymphocytes will be crucial in improving treatment outcomes for immunotherapy.