ESPE Abstracts (2014) 82 FC9.1

Inappropriately High Rates of Cell Proliferation in Diffuse Congenital Hyperinsulinism are Linked to Nuclear Expression of CDK6

Rachel Salisburya, Bing Hana, Zainaba Mohameda,b, Ronald De Krijgerc, Laurienne Gardnera, Julia Gardnera, Karen Cosgrovea, Raja Padidelab, Melanie Newbouldb, Indraneel Banerjeea,b, Neil Hanleya,b & Mark Dunnea

aUniversity of Manchester, Manchester, UK; bCentral Manchester University Hospitals NHS Foundation Trust, Manchester, UK; cUniversity Hospital Dijkzigt, Rotterdam, The Netherlands

Background: Congenital hyperinsulinism of infancy (CHI) mainly arises from loss-of-function mutations in the KATP channel genes. As a consequence, insulin release is uncontrolled and causes persistent or recurrent episodes of hypoglycaemia in neonates. In patients with diffuse-CHI (CHI-D) increased rates of cell proliferation has been reported, but the causes of proliferation are unknown.

Objective/Hypotheses: To assess the extent of cell proliferation and the role of CDK6 in control of the cell cycle in the CHI-D pancreas.

Methods: We used immunostaining in paraffin-embedded samples of CHI-D (n=7, 2–13 months), age-matched control pancreata (n=6, 6 weeks–13 months) and foetal pancreas (10 weeks post-conception) to examine the extent of proliferation in different cell types including α- (glucagon+), β- (insulin+), ductal (SOX9+), and exocrine (GATA4+) cells. Ki67 was used to document cell proliferation and to define the proliferative index of the pancreas through high-content analysis of digital images. The control of cell proliferation was investigated via immunostaining of the cell cycle regulator CDK6.

Results: In controls we found Ki67 staining correlated inversely with age between 6 weeks and 1 year after birth (rs=−0.929, P<0.01). In contrast, proliferation remained elevated in all cell types in CHI-D with SOX9-, GATA4-, and insulin-positive cells reaching statistical significance, P<0.01. By analysing regions of tissue each containing 20 000–30 000 cells we found that, on average, 4.3±0.1% of the CHI pancreas was proliferative (n=3 cases) compared to 36.3±8% of the foetal pancreas. CDK6 was detected in the cytoplasm of control islets where it colocalised with insulin. By comparison, in CHI-D, CDK6 was strongly nuclear in islet-, exocrine- and a sub-fraction of ductal-cells.

Conclusion: CHI-D retains high rates of proliferation in SOX9-, GATA4-, and insulin-positive cell types compared to age-matched controls. Detection of nuclear-localised CDK6 in these cells supports a role for CDK6 in inappropriate cell proliferation.