Insulin and Insulin-like Growth Factor 1 Signaling as a Modulator of MYC Expression in the Meibomian Gland.

Background/

Objectives

Sebaceous carcinomas (SebCAs) of the ocular adnexa, primarily arising from the Meibomian glands, are locally aggressive eyelid tumors with metastatic potential. Upregulation of the oncogene MYC has been demonstrated in SebCA, suggesting a role in tumor initiation and progression. In other epithelial tumors, the insulin and insulin-like growth factor (IGF) signaling (IIS) pathway has been implicated in stem cell renewal via MYC activation and stabilization. This study aimed to evaluate the effects of pharmacologic and genetic modulation of the IIS pathway on MYC expression in human Meibomian gland epithelial cells (HMGECs) and meibocytes of adult C57B6 mice.

Methods

HMGECs were incubated with either IIS activators or inhibitors or were subject to transfection with either an IGF1R plasmid or siRNA before assessments of viability, proliferation, immunostaining, and MYC quantification were performed. Murine eyelids were treated topically with small-molecule IIS modulators prior to tissue harvest for histology, immunolabeling, and qPCR.

Results

HMGECs treated with IIS activators demonstrated downregulated IGF1R and upregulated MYC expression, increased viability and proliferation, and reduced autophagy, while treatment with inhibitors yielded the inverse effects. Incubation with the selective insulin receptor agonist, demethylasterriquinone B1, yielded the most phenotypic variability. IGF1R-overexpressing HMGECs exhibited relative upregulation of both Akt and MYC. Murine eyelids treated with an IIS agonist demonstrated a more mesenchymal phenotype and significantly induced MYC expression.

Conclusions

Collectively, these results suggest that the IIS pathway may represent a novel approach for regulating high MYC expression in SebCA.