Background:Little is known about the tumour suppressive proteins and the underlying mechanisms that suppress colon cancer progression. Homeodomain-containing transcription factor HOXB9 plays an important role in embryogenesis and cancer development. We here aim to uncover the potential role of HOXB9 in the regulation of colon adenocarcinoma progression including epithelial-to-mesenchymal transition.Methods:HOXB9 expression in colon adenocarcinoma cells and patients was analysed by western blot and immunohistochemistry separately. Correlation between HOXB9 expressions with patients' survival was assessed by Kaplan–Meier analysis. HOXB9-regulated target gene expression was determined by RNA sequencing in HOXB9-overexpressing colon adenocarcinoma cells.Results:Elevated HOXB9 expression was identified in well-differentiated colon adenocarcinoma patients and was associated with a better overall patients' survival. Overexpression of HOXB9 inhibited colon adenocarcinoma cell growth, migration, invasion in vitro and tumour growth, liver as well as lung metastases in nude mice; whereas silencing HOXB9 promoted these functions. HOXB9 promoted colon adenocarcinoma differentiation via a mechanism that stimulates mesenchymal-to-epithelial transition, involving downregulation of EMT-promoting transcriptional factors including Snail, Twist, FOXC2 and ZEB1 and upregulation of epithelial proteins including E-cadherin, claudins-1, -4, -7, occludin and ZO-1.Conclusions:HOXB9 is a novel tumour suppressor that inhibits colon adenocarcinoma progression by inducing differentiation. Elevated expression of HOXB9 predicts a longer survival in colon adenocarcinoma patients.

Habitat fragmentation may strongly impact population genetic structure and reduce the genetic diversity and viability of small and isolated populations. The white-headed langur (Trachypithecus leucocephalus) is a critically endangered primate species living in a highly fragmented and human-modified habitat in southern China. We examined the population genetic structure and genetic diversity of the species and investigated the environmental and anthropogenic factors that may have shaped its population structure. We used 214 unique multi-locus genotypes from 41 social groups across the main distribution area of T. leucocephalus, and found strong genetic structure and significant genetic differentiation among local populations. Our landscape genetic analyses using a causal modelling framework suggest that a large habitat gap and geographical distance represent the primary landscape elements shaping genetic structure, yet high levels of genetic differentiation also exist between patches separated by a small habitat gap or road. This is the first comprehensive study that has evaluated the population genetic structure and diversity of T. leucocephalus using nuclear markers. Our results indicate strong negative impacts of anthropogenic land modifications and habitat fragmentation on primate genetic connectivity between forest patches. Our analyses suggest that two management units of the species could be defined, and indicate that habitat continuity should be enforced and restored to reduce genetic isolation and enhance population viability.

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