Programmed Cell Death Ligand 1 Is Enriched in Mammary Stem Cells and Promotes Mammary Development and Regeneration

Regulatory mechanisms of PD-1/PD-L1 in cancers

Immune evasion contributes to cancer growth and progression. Cancer cells have the ability to activate different immune checkpoint pathways that harbor immunosuppressive functions. The programmed death protein 1 (PD-1) and programmed cell death ligands (PD-Ls) are considered to be the major immune checkpoint molecules. The interaction of PD-1 and PD-L1 negatively regulates adaptive immune response mainly by inhibiting the activity of effector T cells while enhancing the function of immunosuppressive regulatory T cells (Tregs), largely contributing to the maintenance of immune homeostasis that prevents dysregulated immunity and harmful immune responses. However, cancer cells exploit the PD-1/PD-L1 axis to cause immune escape in cancer development and progression. Blockade of PD-1/PD-L1 by neutralizing antibodies restores T cells activity and enhances anti-tumor immunity, achieving remarkable success in cancer therapy. Therefore, the regulatory mechanisms of PD-1/PD-L1 in cancers have attracted an increasing attention. This article aims to provide a comprehensive review of the roles of the PD-1/PD-L1 signaling in human autoimmune diseases and cancers. We summarize all aspects of regulatory mechanisms underlying the expression and activity of PD-1 and PD-L1 in cancers, including genetic, epigenetic, post-transcriptional and post-translational regulatory mechanisms. In addition, we further summarize the progress in clinical research on the antitumor effects of targeting PD-1/PD-L1 antibodies alone and in combination with other therapeutic approaches, providing new strategies for finding new tumor markers and developing combined therapeutic approaches.

Stem Cell Origin of Cancer: Clinical Implications beyond Immunotherapy for Drug versus Therapy Development in Cancer Care

Although immunotherapy has revolutionized cancer care, there is still an urgent need to enhance its efficacy and ensure its safety. A correct cancer theory and proper scientific method empower pertinent cancer research and enable effective and efficient drug versus therapy development for patient care. In this perspective, we revisit the concept of immune privilege in a cancer cell versus normal cell, as well as in a cancer stem cell versus normal stem cell. We re-examine whether effective immunotherapies are efficacious due to their anti-cancer and/or immune modulatory mechanisms. We reassess why checkpoint inhibitors (CPIs) are not equal. We reconsider whether one can attribute the utility of immunotherapy to specific cancer subtypes and its futility to certain tumor/immune compartments, components, and microenvironments. We propose ways and means to advance immunotherapy beyond CPIs by combining anti-PD1/L1 with various other treatment modalities according to an appropriate scientific theory, e.g., stem cell origin of cancer, and based on available clinical evidence, e.g., randomized clinical trials. We predict that a stem cell theory of cancer will facilitate the design of better and safer immunotherapy with improved selection of its use for the right patient with the right cancer type at the right time to optimize clinical benefits and minimize potential toxic effects and complications.

Breast cancers co-opt normal mechanisms of tolerance to promote immune evasion and metastasis

Normal developmental processes, such as those seen during embryonic development and postpartum mammary gland involution, can be reactivated by cancer cells to promote immune suppression, tumor growth, and metastatic spread. In mammalian embryos, paternal-derived antigens are at risk of being recognized as foreign by the maternal immune system. Suppression of the maternal immune response toward the fetus, which is mediated in part by the trophoblast, is critical to ensure embryonic survival and development. The postpartum mammary microenvironment also exhibits immunosuppressive mechanisms accompanying the massive cell death and tissue remodeling that occurs during mammary gland involution. These normal immunosuppressive mechanisms are paralleled during malignant transformation, where tumors can develop neoantigens that may be recognized as foreign by the immune system. To circumvent this, tumors can dedifferentiate and co-opt immune-suppressive mechanisms normally utilized during fetal tolerance and postpartum mammary involution. In this review, we discuss those similarities and how they can inform our understanding of cancer progression and metastasis.

Therapeutic potential of neurotrophic factors in Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia among the elderly population. AD is accompanied with the dysregulation of specific neurotrophic factors (NTFs) and their receptors, which plays a critical role in neuronal degeneration. NTFs are small proteins with therapeutic potential for human neurodegenerative diseases. These growth factors are categorized into four families: neurotrophins, neurokines, the glial cell line-derived NTF family of ligands, and the newly discovered cerebral dopamine NTF/mesencephalic astrocyte-derived NTF family. NTFs are capable of preventing cell death in degenerative conditions and can increase the neuronal growth and function in these disorders. Nevertheless, the adverse side effects of NTFs delivery and poor diffusion of these factors in the brain restrict the efficacy of NTFs therapy in clinical situations.

MATERIALS AND METHODS

In this review, we focus on the current advances in the use of NTFs to treat AD and summarize previous experimental and clinical studies for supporting the protective and therapeutic effects of these factors.

CONCLUSION

Based on reports, NTFs are considered as new and promising candidates for treating AD and AD-associated cognitive impairment.