Name of Student:
Peter Raven
Research Supervisor: Dr. Alan So
Title of Presentation: Sonic hedgehog pathway expression in clinical cases of bladder cancers
Abstract
Introduction: Bladder cancer is one of the leading cancers in North America. Approximately 70%
of bladder cancers are initially diagnosed as superficial tumours but following resection 80% will
recur and 20-30% will develop into muscle invasive tumours with potential to metastasize and
invade neighboring tissues. The sonic hedgehog (SHH) signaling pathway is involved in
embryonic developmental processes such as pattern formation, differentiation, proliferation, and
organogenesis. SHH signaling is maintained in adult tissues in the healing response, and instances
of tissue regeneration such as the lumen of the bladder. Aberrant SHH signaling is thought to
contribute to many types of cancer development and progression and may be dis-regulated in
bladder cancers.
Methods: We examined the expression levels of proteins in the SHH pathway and those
associated with the transition from epithelial to mesenchymal cell phenotype (EMT) in tissue
microarrays (TMA) developed from the Urology Clinic at Vancouver General Hospital (TMA
compiled by Dr. Peter Black). These proteins included: SHH ligand, the cell surface SHH receptor
patched (PTCH), the surface bound pathway inhibitor smoothened (SMO), two down-stream
transcription factors Gli 1 and Gli 2, the cell adhesion glycoprotein E-cadherin, and the
mesenchymal cytoskeletal protein Vimentin. The TMA consisted of 64 normal epithelial tissues,
36 cases of tumors without lymph node (LN) metastases, 34 cases of tumors with associated LN
metastases and 17 cases of carcinoma in situ (CIS) with matching benign tissue. All
immunohistochemical staining was graded on a scale from 0 to 3 by a pathologist (L.F.).
Results: SHH ligand was highest in normal epithelial tissues with a decreasing trend as tumors
progressed through severity (normal, CIS, tumour without LN metastases, tumour with LN
metastases, LN metastases alone). The receptor PTCH showed a small decrease in CIS and more
severe tumors. SMO exhibited a marked decrease in CIS and a slow increase back to normal levels
in the more severe tumor samples. Interestingly, Gli1 and Gli2 changed little between cases. The
EMT protein E-cadherin showed little change between cancers and Vimentin staining was
inconclusive. Examination of the tissue cores revealed a distinct difference in both E-cadherin and
Vimentin staining within the same tissue core, suggesting multiple phenotypes of bladder cancer
may be present within a single case. Further analysis to distinguish protein expression differences
between these distinct regions is underway.
Conclusions: Analysis of a bladder cancer tissue microarray has revealed trends unexpected in a
model of enhanced SHH signaling in aggressive and invasive tumors. Specifically, levels of the
Gli 1 and 2 transcription factors were not increased and the membrane bound inhibitor SMO did
not decrease in the more severe cancer cases. This may be due to the presence of distinct cell
phenotypes within single cases as determined from individual tissue cores, suggesting that average
protein expression may be a poor metric for examining bladder cancer. The identification and
evaluation of tumours with unique characteristics, and possibly unique origins, is of utmost
importance for targeted bladder cancer therapies.