pax gene products

The pax (paired box) genes are oncodevelopmental genes regulating transcription and cellular differentiation. They share a DNA-binding motif and are conserved in evolution5.  The nine members of this family are designed as Pax-1 to Pax-9.

Immunohistochemical expression

• pax-2

• most Wilm's tumours3

• renal cell carcinomas:

1. papillary renal cell carcinoma; 12/12, strong staining1
   conventional renal cell carcinomas; 31/33 variable intensity1
   renal oncocytoma; 1(weak)/31
   chromophobe renal cell carcinoma; 1(weak)/31
   urothelial renal carcinoma; 0/41

1.  

• positive in many serous ovarian tumours but negative in most peritoneal malignant mesotheliomas

• pax-3 and pax-7

• some rhabdomyosarcomas with translocations of chromosome 132.

• pax-4:

• endocrine progenitor cells, pancreatic islet cells and pancreatic endocrine tumours

• pax-5: encodes the B-cell specific activator protein, BSAP.

• 50% of lymphoplasmacytoid lymphomas

• Classical Hodgkin lymphoma

• Merkel cell carcinoma and small cell carcinoma

• pax-6:

• pancreatic islet cells and pancreatic endocrine tumours

• pax-8

  • critical to organogenesis in the thyroid, kidney and Mullerian system

  • positive in B-lymphocytes

  • follicular thyroid neoplasms commonly show a t(2;3)(q13;p25) translocation, resulting in a Pax8-pparg fusion gene4. Pparg is a peroxisome proliferator-activated receptor gene. The result is over-expression of pparg, which can be detected by immunohistochemistry in follicular thyroid neoplasms but not in other thyroid tumours4.

  • positive in renal epithelial tumours and urothelial carcinomas

  • positive in many serous ovarian tumours but negative in most peritoneal malignant mesotheliomas.

  • Positive in many pancreatic endocrine tumours, duodenal and rectal carcinoids but negative in ileal and pulmonary carcinoids

References

1 Daniel, L., Lechevallier, E., Giorgi, R., Sichez, H., Zattara-Cannoni, H., Figarella-Branger, D., Coulange, C. Pax-2 expression in adult renal tumors. Human Pathol 2001;32:282-287

2 Sorensen, P. H., Triche, T. J. Gene fusions encoding chimaeric transcription factors in solid tumours Semin Cancer Biol 1996;7:3-14.

3 Tagge, E. P., Hanson, P., Re, G. G., Othersen, H. B., Jr., Smith, C. D., Garvin, A. J. Paired box gene expression in Wilms' tumor. J Pediatr Surg 1994;29:134-141

4 Nikiforova, M. N., P. W. Biddinger, et al. (2002). "PAX8-PPARgamma rearrangement in thyroid tumors: RT-PCR and immunohistochemical analyses." Am J Surg Pathol 26(8): 1016-23.

5 Dong HY, Liu W, Cohen P, et al. B-cell specific activation protein encoded by the PAX-5 gene is commonly expressed in merkel cell carcinoma and small cell carcinomas. Am J Surg Pathol 2005; 29:687-92

This page last revised 16.8.2005.

©SMUHT/PW Bishop