Autophagy in Osteosarcoma

Osteosarcoma (OS) remains a difficult disease to treat. The standard chemotherapy regimen has not improved survival for the past three decades. Resistance to chemotherapy remains a challenge and constitutes a major concern to clinical investigators. Autophagy has been recognized as a survival mechanism implicated in resistance to chemotherapy. We previously demonstrated chemotherapy to induce autophagy in OS. However, whether induction of autophagy will lead to survival or death has been the focus of many laboratories. Autophagy is a very context-dependent process, and no specific biomarker has been identified to define whether the process will lead to survival or death. In the present chapter, we present some of the mechanisms involved in the process of autophagy and summarize some of the most recent work related to autophagy in OS and the challenges encountered with the use of old and new autophagy inhibitors.

[LAP (LC3-associated phagocytosis): phagocytosis or autophagy?]

Phagocytosis and macroautophagy, named here autophagy, are two essential mechanisms of lysosomal degradation of diverse cargos into membrane structures. Both mechanisms are involved in immune regulation and cell survival. However, phagocytosis triggers degradation of extracellular material whereas autophagy engulfs only cytoplasmic elements. Furthermore, activation and maturation of these two processes are different. LAP (LC3-associated phagocytosis) is a form of phagocytosis that uses components of the autophagy pathway. It can eliminate (i) pathogens, (ii) immune complexes, (iii) threatening neighbouring cells, dead or alive, and (iv) cell debris, such as POS (photoreceptor outer segment) and the midbody released at the end of mitosis. Cells have thus optimized their means of elimination of dangerous components by sharing some fundamental elements coming from the two main lysosomal degradation pathways.

Sense Ginsenosides From Ginsengs: Structure-Activity Relationship in Autophagy

The term ginseng refers to the dried roots of several plants belonging to the genus Panax of the Araliaceae family. The 3 major commercial ginsengs are Panax notoginseng (Burk.) F.H. Chen (Notoginseng), P. ginseng C.A. Meyer (Ginseng), and P. quinquefolius L. (American ginseng), which have been used as herbal medicines. Over 18,000 papers on ginsengs have been published on the basis of their structural diversity and biological activities. Many reviews have summarized the phytochemistry, pharmacology, and clinical use of ginsengs, but the structure-activity relationship (SAR) of ginsenosides from ginsengs in autophagy is unavailable. Herein, we review the structural diversity of ginsenosides, especially the ones in notoginseng, and the SAR in autophagic activity is discussed in detail.

[Regulation of immunity and inflammation by autophagy: « All is well, all is fine, all goes as well as possible»]

Autophagy is a lysosomal degradation mechanism which helps to control intracellular infections and contributes to the regulation of innate and adaptive immune responses. Defects in autophagy lead to exacerbated proliferation of microorganisms and/or to excessive immune responses which are both highly deleterious. Thus, infectious and chronic inflammatory human diseases, such as Crohn's disease, are often associated with inappropriate modulation of autophagy, which is mainly linked to autophagy-associated gene polymorphisms. In this review, we highlight the current understanding of role of autophagy in infections and immunity.