KIBRA attains oncogenic activity by repressing RASSF1A

KIBRA connects Hippo signaling and cancer

The Hippo signaling pathway is a tumor suppressor pathway that plays an important role in tissue homeostasis and organ size control. KIBRA is one of the many upstream regulators of the Hippo pathway. It functions as a tumor suppressor by positively regulating the core Hippo kinase cascade. However, there are accumulating shreds of evidence showing that KIBRA has an oncogenic function, which we speculate may arise from its functions away from the Hippo pathway. In this review, we have attempted to provide an overview of the Hippo signaling with a special emphasis on evidence showing the paradoxical role of KIBRA in cancer.

Intrinsic disorder and amino acid specificity modulate binding of the WW2 domain in kidney and brain protein (KIBRA) to synaptopodin

The second WW domain (WW2) of the kidney and brain scaffolding protein, KIBRA, has an isoleucine (Ile-81) rather than a second conserved tryptophan and is primarily unstructured. However, it adopts the canonical triple-stranded antiparallel β-sheet structure of WW domains when bound to a two-PPXY motif peptide of the synaptic protein Dendrin. Here, using a series of biophysical experiments, we demonstrate that the WW2 domain remains largely disordered when bound to a 69-residue two-PPXY motif polypeptide of the synaptic and podocyte protein synaptopodin (SYNPO). Isothermal titration calorimetry and CD experiments revealed that the interactions of the disordered WW2 domain with SYNPO are significantly weaker than SYNPO's interactions with the well-folded WW1 domain and that an I81W substitution in the WW2 domain neither enhances binding affinity nor induces substantial WW2 domain folding. In the tandem polypeptide, the two WW domains synergized, enhancing the overall binding affinity with the I81W variant tandem polypeptide 2-fold compared with the WT polypeptide. Solution NMR results showed that SYNPO binding induces small but definite chemical shift perturbations in the WW2 domain, confirming the disordered state of the WW2 domain in this complex. These analyses also disclosed that SYNPO binds the tandem WW domain polypeptide in an antiparallel manner, that is, the WW1 domain binds the second PPXY motif of SYNPO. We propose a binding model consisting of a bipartite interaction mode in which the largely disordered WW2 forms a "fuzzy" complex with SYNPO. This binding mode may be important for specific cellular functions.

Interleukin-6 Receptor (IL-6R) Expression in Human Gastric Carcinoma and its Clinical Significance

The aim of the study is to analyse the expression of Interleukin-6 receptor in different human gastric tissue and to correlate with the clinicopathological features of the patients. Immunohistochemistry was done against the IL-6R antibody and the Q-score was calculated from the staining pattern. Higher Q-scores were observed in tumour cells than the adjacent normal cells which were statistically significant. We also observed a significant correlation between the expressions of IL-6R and the clinicopathological features These findings suggest that IL-6R may represent as a therapeutic target for gastric carcinoma and serve as a prognostic indicator, as well.

KIBRA; a novel biomarker predicting recurrence free survival of breast cancer patients receiving adjuvant therapy

BACKGROUND

This study was carried out to evaluate the prognostic value of KIBRA in breast cancer.

METHODS

This retrospective study included breast cancer patients who sought the services of the immunohistochemistry laboratory of our unit from 2006 to 2015. Tissue microarrays were constructed and immunohistochemical staining was done to assess the KIBRA expression. The Kaplan-Meier model for univariate and Cox-regression model with backward stepwise factor retention method for multivariate analyses were used. Chi square test was used to find out the associations with the established prognostic features.

RESULTS

A total of 1124 patients were included in the study and KIBRA staining of 909 breast cancers were available for analysis. Cytoplasmic KIBRA expression was seen in 39.5% and nuclear expression in 44.8%. Overall KIBRA-low breast cancers accounted for 41.5%. KIBRA nuclear expression was significantly associated with positive ER and PR expression. Luminal breast cancer patients who had endocrine therapy and KIBRA-low expression had a RFS disadvantage over those who were positive for KIBRA (p = 0.02). Similarly, patients who received chemotherapy and had overall KIBRA-low expression also demonstrated a RFS disadvantage compared to those who had overall positive KIBRA expression (p = 0.018). This effect of KIBRA was independent of the other factors considered for the model.

CONCLUSION

Overall low-KIBRA expression has an independent effect on the RFS and predicts the RFS outcome of luminal breast cancer patients who received endocrine therapy and breast cancer patients who received chemotherapy.