Autophagy: friend or foe in breast cancer development, progression, and treatment

Abstract

Autophagy is a catabolic process responsible for the degradation and recycling of long-lived proteins and organelles by lysosomes. This degradative pathway sustains cell survival during nutrient deprivation, but in some circumstances, autophagy leads to cell death. Thereby, autophagy can serve as tumor suppressor, as the reduction in autophagic capacity causes malignant transformation and spontaneous tumors. On the other hand, this process also functions as a protective cell-survival mechanism against environmental stress causing resistance to antineoplastic therapies. Although autophagy inhibition, combined with anticancer agents, could be therapeutically beneficial in some cases, autophagy induction by itself could lead to cell death in some apoptosis-resistant cancers, indicating that autophagy induction may also be used as a therapy. This paper summarizes the most important findings described in the literature about autophagy and also discusses the importance of this process in clinical settings.

Figure 1

Different mechanisms to recycle molecules and organelles in the eukaryotic cell. Eukaryotes have two major protein degradation systems within cells. One is the ubiquitin-proteasome system, which accounts for the selective degradation of most short-lived proteins. The other is the autophagy, the primary means for the degradation of cytoplasmic constituents in the lysosome.