Different APC genotypes in proximal and distal sporadic colorectal cancers suggest distinct WNT/ß-catenin signalling thresholds for tumourigenesis.

Biallelic protein-truncating mutations in the adenomatous polyposis coli (APC) gene are prevalent in sporadic colorectal cancer (CRC). Mutations may not be fully inactivating, instead producing WNT/ß-catenin signalling levels 'just-right' for tumourigenesis. However, the spectrum of optimal APC genotypes accounting for both hits, and the influence of clinicopathological features on genotype selection remain undefined. We analysed 630 sporadic CRCs for APC mutations and loss of heterozygosity (LOH) using sequencing and single-nucleotide polymorphism microarrays, respectively. Truncating APC mutations and/or LOH were detected in 75% of CRCs. Most truncating mutations occurred within a mutation cluster region (MCR; codons 1282-1581) leaving 1-3 intact 20 amino-acid repeats (20AARs) and abolishing all Ser-Ala-Met-Pro (SAMP) repeats. Cancers commonly had one MCR mutation plus either LOH or another mutation 5' to the MCR. LOH was associated with mutations leaving 1 intact 20AAR. MCR mutations leaving 1 vs 2-3 intact 20AARs were associated with 5' mutations disrupting or leaving intact the armadillo-repeat domain, respectively. Cancers with three hits had an over-representation of mutations upstream of codon 184, in the alternatively spliced region of exon 9, and 3' to the MCR. Microsatellite unstable cancers showed hyper-mutation at MCR mono- and di-nucleotide repeats, leaving 2-3 intact 20AARs. Proximal and distal cancers exhibited different preferred APC genotypes, leaving a total of 2 or 3 and 0 to 2 intact 20AARs, respectively. In conclusion, APC genotypes in sporadic CRCs demonstrate 'fine-tuned' interdependence of hits by type and location, consistent with selection for particular residual levels of WNT/ß-catenin signalling, with different 'optimal' thresholds for proximal and distal cancers.

Wound healing response is a major contributor to the severity of cutaneous leishmaniasis in the ear model of infection.

In the conventional mouse model for cutaneous leishmaniasis involving infection with stationary phase Leishmania major promastigotes at the base of the tail, mice congenic for leishmaniasis resistance loci designated lmr1,2,3 cured their lesions more rapidly and laid down more ordered collagen fibres than the susceptible parental BALB/c mice, while the opposite was the case for the congenic mice carrying the susceptibility loci on the resistant C57BL/6 background. In that model, we showed that wound healing and not T cell responses played a major role in determining the resolution of skin infection. Here, we show a similar disease phenotype in the mouse model that mimics more closely the situation in humans, that is, strictly intradermal infection in the ear pinna with small numbers of metacyclic promastigotes. The data show that at the site of infection the innate and adaptive immune responses act in concert to clear parasites, and induce tissue repair and wound healing. Importantly, the data show that the host responses controlled by the lmr loci, which act locally to control infection in the skin, are distinct from the host responses operating systemically in the draining lymph node.

Cutaneous leishmaniasis in red kangaroos: isolation and characterisation of the causative organisms.

This is the first report of cutaneous leishmaniasis in kangaroos where infection was acquired within Australia. The diagnosis is based on the clinical criteria used for humans, the lesion histopathology, the detection and isolation of parasites from the lesions, and the analysis of the small subunit ribosomal RNA genes using the polymerase chain reaction. Despite a clear indication that the parasites belong to the genus Leishmania, no assignation to a known Leishmania species could be made using these or other less conserved genetic loci such as the non-transcribed spacer of the mini-exon repeat. As is the case in humans, some but not all animals harbouring lesions had antibodies to the isolated parasites or to several other Leishmania species. The isolated parasites displayed two well characterised Leishmania glycoconjugates, the lipophosphoglycan and proteophosphoglycan. They were infectious for mouse macrophages in vitro and established long-term infection at 33 degrees C but not at 37 degrees C. Our findings raise the possibility of transmission to humans, which may be unrecognised and suggest the possibility that imported species of Leishmania could become endemic in Australia.