Abstract
Background and AimsColorectal cancer (CRC) arises via multiple genetic changes. Mutation of the tumour suppressor gene APC, a key regulator of Wnt signalling, is recognised as a frequent early driving mutation in CRC. We have previously shown that conditional loss of Apc within the murine small intestine (Apcfloxmice) results in acute Wnt signalling activation, altered crypt-villus architecture and many hallmarks of neoplasia. Our transctipomic profiling (Affymetrix Microarrays) and proteomic profiling (iTRAQ-QSTAR) of Apc-deficient intestine inferred the involvement of High Mobility Group Box 1 (Hmgb1) in CRC pathogenesis. Here we assess the contribution of HMGB1 to the crypt progenitor phenotype seen following Apc loss.ResultsElevated HMGB1 was confirmed in intestinal epithelia and serum following conditional loss of Apc. Treatment of Apcflox mice with anti-HMGB1 neutralising antibody significantly reduced many of the crypt progenitor phenotypes associated with Apc loss; proliferation and apoptosis levels were reduced, cell differentiation was restored and the expansion of stem cell marker expression was eradicated.MethodsHmgb1 levels in intestinal epithelia and serum in Apcflox and ApcMin mice were assessed using qRT-PCR, Western blot and ELISA assays. The functional importance of elevated extracellular Hmgb1 was assessed using an anti-HMGB1 neutralising antibody in Apcflox mice.ConclusionsHMGB1 is expressed and secreted from intestinal epithelial cells in response to Wnt signalling activation. This secreted HMGB1 is required to maintain nearly all aspects of the crypt progenitor phenotype observed following Apc loss and add to the body of accumulating evidence indicating that targeting HMGB1 may be a viable novel therapeutic approach.
Highlights
Wnt signalling is a key pathway which regulates normal intestinal homeostasis [1]
Treatment of Apcflox mice with anti-HMGB1 neutralising antibody significantly reduced many of the crypt progenitor phenotypes associated with Adenomatous polyposis coli (Apc) loss; proliferation and apoptosis levels were reduced, cell differentiation was restored and the expansion of stem cell marker expression was eradicated
HMGB1 is expressed and secreted from intestinal epithelial cells in response to Wnt signalling activation. This secreted HMGB1 is required to maintain most aspects of the crypt progenitor phenotype observed following Apc loss and add to the body of accumulating evidence indicating that targeting HMGB1 may be a viable novel therapeutic approach
Summary
Wnt signalling is a key pathway which regulates normal intestinal homeostasis [1]. It is widely recognised that deregulation of the Wnt pathway underpins the early stages of colorectal cancer [2, 3]. Transcriptomic Affymetrix microarray analysis [5, 6] and proteomic profiling using iTRAQ-QSTAR [7] to identify genes that are mis-regulated at these early stages of neoplasia following the loss of Apc, and thereby identify factors that potentially contribute to CRC pathogenesis. These analyses have inferred the involvement of the High Mobility Group Box 1 (Hmgb1) gene. We have previously shown that conditional loss of Apc within the murine small intestine (Apcfloxmice) results in acute Wnt signalling activation, altered crypt-villus architecture and many hallmarks of neoplasia. We assess the contribution of HMGB1 to the crypt progenitor phenotype seen following Apc loss
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