Introduction

Autophagy is a mechanism that degrades large damaged organelles and misfolded proteins to maintain the homeostasis in all cells. It plays double-faceted roles in tumourigenesis and prevention of various cancers. In our side observation of investigating the prognostic value of autophagy in colorectal cancer (CRC), we found high expression of autophagy proteins (LC3A, LC3B, and p62/SQSTM1) in the colonic ganglion cells. To our best understanding, this is the first paper reporting such finding. Materials and methods: Formalin-fixed paraffin-embedded (FFPE) CRC tissues blocks were retrieved and confirmed by haematoxylin & eosin (H&E) staining. Immunohistochemistry (IHC) targeting autophagy proteins (LC3A, LC3B, and p62/SQSTM1) was then performed followed by pathological examination. Results: All three autophagy proteins were present in both normal and tumour tissues of CRC patients. Interestingly, high expression of autophagy proteins in colonic ganglion cells was consistently seen regardless of tissue type (normal or cancer) or tumour site (caecum, ascending, transverse, descending, sigmoid colon and rectum).

Conclusions

This work highlights the high autophagic activities in human colonic ganglion cells.

1. Pang, S. W., Awi, N. J., Yap, H. Y., & Teow, S. Y. (2018). Cell-based assays for evaluation of autophagy in cancers. In R. A. Mehanna (Ed.), Cell culture (pp. 75–96). IntechOpen.
2. Santana-Codina, N., Mancias, J. D., & Kimmelman, A. C. (2017). The role of autophagy in cancer. Annual Review of Cancer Biology, 1, 19–39.
3. White, E. (2015). The role for autophagy in cancer. Journal of Clinical Investigation, 125(1), 42–46.
4. Mokarram, P., Albokashy, M., Zarghooni, M., et al. (2017). New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets. Autophagy, 13(5), 781–819.
5. Gil, J., Pesz, K. A., & Sąsiadek, M. (2016). May autophagy be a novel biomarker and antitumor target in colorectal cancer? Biomarkers in Medicine, 10(10), 1081–1094.
6. Boya, P. (2017). Why is autophagy good for retinal ganglion cells? Eye, 31(2), 185–190.
7. Lee, K., Hong, S., Seong, G. J., & Kim, C. Y. (2016). Cigarette smoke extract causes injury in primary retinal ganglion cells via apoptosis and autophagy. Current Eye Research, 41(10), 1367–1372.
8. Li, H. Y., Huang, M., Luo, Q. Y., Hong, X., Ramakrishna, S., & So, K. F. (2019). Lycium barbarum (wolfberry) increases retinal ganglion cell survival and affects both microglia/macrophage polarization and autophagy after rat partial optic nerve transection. Cell Transplantation.
9. Sivridis, E., Koukourakis, M. I., Zois, C. E., et al. (2010). LC3A-positive light microscopy detected patterns of autophagy and prognosis in operable breast carcinomas. American Journal of Pathology, 176(5), 2477–2489.
10. Kim, S. H., Munemasa, Y., Kwong, J. M. K., et al. (2008). Activation of autophagy in retinal ganglion cells. Journal of Neuroscience Research, 86(13), 2943–2951.
11. Knöferle, J., Koch, J. C., Ostendorf, T., et al. (2010). Mechanisms of acute axonal degeneration in the optic nerve in vivo. Proceedings of the National Academy of Sciences, 107(13), 6064–6069.
12. Rodríguez-Muela, N., & Boya, P. (2012). Axonal damage, autophagy and neuronal survival. Autophagy, 8(2), 286–288.
13. Lin, W. J., & Kuang, H. Y. (2014). Oxidative stress induces autophagy in response to multiple noxious stimuli in retinal ganglion cells. Autophagy, 10(10), 1695–1701.
14. Rubinsztein, D. C., Mariño, G., & Kroemer, G. (2011). Autophagy and aging. Cell, 146(5), 682–695.