Abstract 2908: A sensitive immunohistochemistry method for in vivo autophagy biomarker detection and pharmacodynamic studies

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Immunohistochemistry (IHC) is a powerful tool for studying pharmacodynamic biomarkers in tissue samples. However, IHC using standard methodologies to monitor autophagy has met with limited success due to the technical difficulties involved in detecting transient and low abundance autophagy markers. To address this issue, we have applied a highly sensitive IHC method using a tyramide-based signal amplification system to detect autophagy pathway proteins in paraffin sections of human tumor cell line and xenograft tissues. We were able to detect basal levels of punctate staining LC3B and NBR1 on both HCT116 and Calu-6 xenograft tumors using the tyramide-based signal amplification method whereas standard IHC showed little to no specific staining. Consistent with in vitro observations, lipidated LC3B, as detected by puncta formation, was elevated following autophagy induction using mTOR inhibitor treatment, and decreased following ATG7 knockout or knock down in both cell lines and xenograft tumors. As a result of autophagy pathway interruption following ATG7 inhibition, accumulation of the adapter proteins NBR1 and p62 was also detected. Our data demonstrate the feasibility of using high sensitivity IHC assays to reliably measure low abundant autophagy markers in xenograft tissues and may aid the exploration of autophagy regulation in cancer development. Citation Format: Yu Yang, Natalie Roy D'Amore, Jouhara Chouitar, Jie Yu, Kristine Burke, Zhongmin Xiang, Lunyin Yu, Kerri Lasky, James Brownell, Chris Simpson, Evan Luongo, Doug Bowman, Stephen Tirrell, Helen He. A sensitive immunohistochemistry method for in vivo autophagy biomarker detection and pharmacodynamic studies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2908. doi:10.1158/1538-7445.AM2015-2908