Assessing Autophagy in Archived Tissue or How to Capture Autophagic Flux from a Tissue Snapshot

Abstract

Autophagy is a highly conserved degradation mechanism that is essential for maintaining cellular homeostasis. In human disease, autophagy pathways are frequently deregulated and there is immense interest in targeting autophagy for therapeutic approaches. Accordingly, there is a need to determine autophagic activity in human tissues, an endeavor that is hampered by the fact that autophagy is characterized by the flux of substrates whereas histology informs only about amounts and localization of substrates and regulators at a single timepoint. Despite this challenging task, considerable progress in establishing markers of autophagy has been made in recent years. The importance of establishing clear-cut autophagy markers that can be used for tissue analysis cannot be underestimated. In this review, we attempt to summarize known techniques to quantify autophagy in human tissue and their drawbacks. Furthermore, we provide some recommendations that should be taken into consideration to improve the reliability and the interpretation of autophagy biomarkers in human tissue samples.

Autophagy-Related MicroRNA: Tumor miR-125b and Thyroid Cancers

“…Some components of the autophagic machinery have important non-autophagic cellular functions. High MAP1LC3B levels could result from cancer progression and reflect the low sensitivity of anti-cancer therapy [ 87 ].…”

Chaperone-Mediated Autophagy Markers LAMP2A and HSPA8 in Advanced Non-Small Cell Lung Cancer after Neoadjuvant Therapy

“…The available and established methods for examining autophagy include transmission electron microscopy, Western blotting, flow cytometry, immunofluorescence and immunohistochemistry (IHC) [39]. Due to the dynamic nature of autophagy in the cell (autophagic flux), functional assays are the most suitable methods for measuring autophagic activity.…”

The Macro-Autophagy-Related Protein Beclin-1 Immunohistochemical Expression Correlates With Tumor Cell Type and Clinical Behavior of Uveal Melanoma

“…Some considerations have to be made, before any conclusion at this regard may be got. To date, there is still the lack of robust markers, improved staining protocols, and standardized interpretation to measure autophagy activity in archived tissue, and we must interpret our data with caution, strictly integrating them with clinical and follow-up data ( 22 ).…”

“…Up to now, its role in cancer remains controversial, particularly for its relationship with prognosis. Three main dynamic autophagy pathways exist: chaperone-mediated autophagy (CMA), microautophagy, and macroautophagy ( 22 ). CMA is a selective multistep autophagy pathway that modulates the turnover of soluble cytosolic proteins, delivering them directly to lysosomes for degradation, without formation of vesicles ( 23 ).…”

“…Up to now, its role in cancer remains controversial, particularly for its relationship with prognosis. Three main dynamic autophagy pathways exist: chaperone-mediated autophagy (CMA), microautophagy, and macroautophagy (22).…”