Autophagy and autophagy-related pathways in cancer

Maintenance of protein homeostasis and organelle integrity and
function is critical for cellular homeostasis and cell viability. Autophagy
is the principal mechanism that mediates the delivery of various
cellular cargoes to lysosomes for degradation and recycling. A myriad
of studies demonstrate important protective roles for autophagy
against disease. However, in cancer, seemingly opposing roles of
autophagy are observed in the prevention of early tumour development
versus the maintenance and metabolic adaptation of established and
metastasizing tumours. Recent studies have addressed not only the
tumour cell intrinsic functions of autophagy, but also the roles of
autophagy in the tumour microenvironment and associated immune
cells. In addition, various autophagy-related pathways have been
described, which are distinct from classical autophagy, that utilize
parts of the autophagic machinery and can potentially contribute to
malignant disease. Growing evidence on how autophagy and related
processes affect cancer development and progression has helped
guide efforts to design anticancer treatments based on inhibition or
promotion of autophagy. In this Review, we discuss and dissect these
different functions of autophagy and autophagy-related processes
during tumour development, maintenance and progression. We outline
recent findings regarding the role of these processes in both the tumour
cells and the tumour microenvironment and describe advances in
therapy aimed at autophagy processes in cancer