RAS and BRAF genes as biomarkers and target for personalised colorectal cancer therapy: An update.

Colorectal cancer (CRC) remains among the most commonly diagnosed cancers and has been on the rise. It is also one of the most lethal diseases globally, being the third leading cause of cancerrelated death. Depending on the stages and disease conditions, CRC is treated by surgery, chemo-, radio-therapy, immunotherapy or in combination. However, these therapies have subpar results with unwanted side effects, hence continuous effort is ongoing to explore new type of therapeutic modalities. Among the sub-types of CRC, KRAS, BRAF and NRAS mutated CRC comprise approximately 43%, 10% and 3% of the total cases, respectively. These mutations are associated with tumour progression and anti-epidermal growth factor receptor (EGFR) treatment resistance. Due to their important role in CRC, these genes have thus become targets in the development of novel treatments. In this paper, we discuss the current and upcoming treatment on CRC by targeting these mutated genes, with more focus on KRAS and BRAF due to the higher occurrence of mutations in CRC.

Association between autophagy and KRAS mutation with clinicopathological variables in colorectal cancer patients.

Autophagy is a host defensive mechanism responsible for eliminating harmful cellular components through lysosomal degradation. Autophagy has been known to either promote or suppress various cancers including colorectal cancer (CRC). KRAS mutation serves as an important predictive marker for epidermal growth factor receptor (EGFR)-targeted therapies in CRC. However, the relationship between autophagy and KRAS mutation in CRC is not well-studied. In this single-centre study, 92 formalin-fixed paraffin-embedded (FFPE) tissues of CRC patients (42 Malaysian Chinese and 50 Indonesian) were collected and KRAS mutational status was determined by quantitative PCR (qPCR) (n=92) while the expression of autophagy effector (p62, LC3A and LC3B) was examined by immunohistochemistry (IHC) (n=48). The outcomes of each were then associated with the clinicopathological variables (n=48). Our findings demonstrated that the female CRC patients have a higher tendency in developing KRAS mutation in the Malaysian Chinese population (p<0.05). Expression of autophagy effector LC3A was highly associated with the tumour grade in CRC (p<0.001) but not with other clinicopathological parameters. Lastly, the survival analysis did not yield a statistically significant outcome. Overall, this small cohort study concluded that KRAS mutation and autophagy effectors are not good prognostic markers for CRC patients.

High expression of LC3A, LC3B, and p62/SQSTM1 autophagic proteins in human colonic ganglion cells.

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.

Hepatitis B Virus Genotype G forms core-like particles with unique structural properties.

We have determined the structure of the core capsid of an unusual variant of hepatitis B virus, genotype G (HBV/G) at 14Å resolution, using cryo-electron microscopy. The structure reveals surface features not present in the prototype HBV/A genotype. HBV/G is novel in that it has a unique 36-bp insertion downstream of the core gene start codon. This results in a twelve amino acid insertion at the N-terminal end of the core protein, and two stop codons in the precore region that prevent the expression of HBeAg. HBV/G replication in patients is associated with co-infection with another genotype of HBV, suggesting that HBV/G may have reduced replication efficiency in vivo. We localized the N-terminal insertion in HBV/G and show that it forms two additional masses on the core surface adjacent to each of the dimer-spikes and have modelled the structure of the additional residues within this density. We show that the position of the insertion would not interfere with translocation of nucleic acids through the pores to the core interior compartment. However, the insertion may partially obscure several residues on the core surface that are known to play a role in envelopment and secretion of virions, or that could affect structural rearrangements that may trigger envelopment after DNA second-strand synthesis.