X-Ray of Excised Cancerous Breast Tissue Does Not Affect Clinical Biomarker Expression.

CONTEXT: College of American Pathologists (CAP) and the American Society of Clinical Oncology have emphasized the need to reduce preanalytic variables for evaluating predictive biomarker expression in breast cancer. Postoperative x-ray of excised breast tissue is commonplace, yet is a variable that has not been investigated previously. We asked whether such radiation affects expression of relevant biomarkers. DESIGN: A previous study found that human breast cancers grown in mice demonstrate the same immunohistochemical and molecular profiles as the original tumors. Thirteen patient-derived xenografts were harvested fresh and divided for specimen radiography and a matched nonirradiated control, while following CAP/ASCO guidelines for cold ischemia time and fixation. Samples were processed in a tissue microarray for immunohistochemistry. Estrogen receptor (ER), progesterone receptor (PR), p53, and Ki67 staining was evaluated using an optimized scoring algorithm performed on digitally scanned slides. Samples were also scored manually by a blinded pathologist using the H-score method, and HER2 by the CAP/ASCO 2013 protocol. Histologic scores were compared by analysis of variance. RESULTS: There was no significant difference in quantity or intensity of staining between irradiated and nonirradiated samples for estrogen receptor (P=0.28), p53 (P=0.96), and Ki67 (P=0.94). A small but statistically significant difference was observed for PR (P=0.0058). HER2 staining was similarly unchanged in the 1 tumor exhibiting 3+ staining. CONCLUSIONS: Our study demonstrates that x-ray of breast carcinomas does not significantly affect the expression of predictive biomarkers, with the exception of PR for unclear reasons. It also highlights the utility of the patient-derived xenograft model for biomarker studies.

MYC Drives Progression of Small Cell Lung Cancer to a Variant Neuroendocrine Subtype with Vulnerability to Aurora Kinase Inhibition.

Loss of the tumor suppressors RB1 and TP53 and MYC amplification are frequent oncogenic events in small cell lung cancer (SCLC). We show that Myc expression cooperates with Rb1 and Trp53 loss in the mouse lung to promote aggressive, highly metastatic tumors, that are initially sensitive to chemotherapy followed by relapse, similar to human SCLC. Importantly, MYC drives a neuroendocrine-low "variant" subset of SCLC with high NEUROD1 expression corresponding to transcriptional profiles of human SCLC. Targeted drug screening reveals that SCLC with high MYC expression is vulnerable to Aurora kinase inhibition, which, combined with chemotherapy, strongly suppresses tumor progression and increases survival. These data identify molecular features for patient stratification and uncover a potential targeted treatment approach for MYC-driven SCLC.