HMGB1 Deficiency Occurs in a Broad Range of Human Cancers and Is Often Associated with Unfavorable Tumor Phenotype.

Background/Objectives: Aberrant expression of high-mobility group protein B1 (HMGB1) has been linked to cancer development and progression. Methods: To better comprehend the role of HMGB1 expression in cancer, a tissue microarray containing 14,966 samples from 134 different tumor entities and 608 samples of 76 different normal tissue types was analyzed by immunohistochemistry. Results: Strong HMGB1 staining occurred in almost all normal cell types and in most cancers. Of 11,808 evaluable cancers, only 7.8% showed complete absence of HMGB1 staining (HMGB1 deficiency) while 9.9% showed 1+, 25.0% showed 2+, and 57.2% showed 3+ HMGB1 positivity. Absence of HMGB1 staining mostly occurred in pheochromocytoma (90.0%), seminoma (72.4%), gastrointestinal stromal tumor (28.6%), adrenal cortical carcinoma (25.0%), and Hodgkin's lymphoma (25.0%). Low HMGB1 staining was linked to poor histologic grade (p < 0.0001), advanced pT stage (p < 0.0001), high UICC stage (p < 0.0001), and distant metastasis (p = 0.0413) in clear cell renal cell carcinoma, invasive tumor growth in urothelial carcinoma (pTa vs. pT2-4, p < 0.0001), mismatch repair deficiency (p = 0.0167) in colorectal cancers, and advanced pT stage in invasive breast carcinoma of no special type (p = 0.0038). Strong HMGB1 staining was linked to nodal metastases in high-grade serous ovarian carcinomas (p = 0.0213) and colorectal adenocarcinomas (p = 0.0137), as well as to poor histological grade in squamous cell carcinomas (p = 0.0010). Conclusions: HMGB1 deficiency and reduced HMGB1 expression occur in a broad range of different tumor entities. Low rather than strong HMGB1 staining is often linked to an aggressive tumor phenotype. Whether HMGB1 deficiency renders cells susceptible to specific drugs remains to be determined.