Transgenic overexpression of the oncofetal RNA binding protein KOC leads to remodeling of the exocrine pancreas.

Abstract

To elucidate the function of the oncofetal RNA-binding protein, K-homologous (KH) domain containing protein overexpressed in cancer (KOC), we studied the effect of a constitutive reexpression of KOC in transgenic mice. Transgenic mouse lines expressing KOC under the control of the mouse metallothionein promoter were generated and were shown to express the 69-kilodalton protein. Two mouse lines with moderate to strong gene expression of the transgene were further analyzed. The pancreas of KOC-transgenic mice showed progressive morphologic alterations, including an increased proliferation of acinar cells, acinar-ductal metaplasia, net loss of acinar tissue, and the appearance of numerous interstitial cells. Acinar-ductal metaplasia led to the development of duct-like structures exhibiting the characteristics of normal intralobular ducts. Interstitial cells expressed markers of endocrine or ductal differentiation. Nerve growth factor alpha (NGF-alpha) and the GTPase kir/Gem were identified as potential targets of KOC by expression profiling analyses. Reexpression of KOC in the transgenic model is apparently incompatible with the maintenance of a fully differentiated, adult acinar phenotype and may lead to a more fetal ductal phenotype via acinar-ductal metaplasia. This and the appearance of interstitial cells with a ductal and endocrine differentiation capacity suggest that transgenic reexpression of the oncofetal gene KOC may recapitulate a developmental program active during embryogenesis.