Development of a HER1 assay using individual human hair follicles

Abstract

3044 Background: Previous reports have described reduction of HER1 phosphorylation and phosphorylation of proteins downstream of HER1 in the skin and the hair follicles of patients treated with HER1 inhibitors such as erlotinib. Methods: Individual hairs from normal volunteers were collected at various time points and fixed. Proteins from each hair follicle was transferred to multiple P-FILM membranes. The membranes were blotted with antibodies to HER1, pHER1, ERK and pERK. Fluorescent images were quantitated using image analysis software. Results: Human hair collected from three regions of the body showed different levels of detectable protein. Scalp hair showed the highest, consistent level of both total protein and staining by antibodies to HER1 signal transduction proteins. Detection of HER1 signal transduction proteins in fixed hair samples was stable for greater than two weeks. Hair samples from five individuals showed approximately four-fold intrasubject differences in HER1 signal intensity. Hairs collected from the same individual at one time point gave a pHER1/HER1 ratio with a %CV of approximately 20%. Hairs collected from the same individual collected at different time points over a two week period showed a similar variability in the pHER1/HER1 ratio. Based upon this intrasample variability, a sample size of four hair follicles per subject and time point was selected for future studies. Conclusions: HER1 signal transduction phosphoproteins could be quantitated from individual scalp hair follicles. The level of HER1 phosphoproteins was similar in hairs collected from an individual at the same time and at various time points over a period of two weeks. The use of hair is minimally invasive, in comparison to skin biopsies, and offers an approach to quantitate the pharmacodynamics of HER1 inhibitors, such as erlotinib, thereby offering the possibility of optimizing dose and treatment scheduling. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration 20/20 Gene Systems; OSI Pharmaceuticals OSI Pharmaceuticals OSI Pharmaceuticals