Hyper-phosphorylation of Rb S249 together with CDK5R2/p39 overexpression are associated with impaired cell adhesion and epithelial-to-mesenchymal transition: Implications as a potential lung cancer grading and staging biomarker.

Prediction of lung cancer metastasis relies on post-resection assessment of tumor histology, which is a severe limitation since only a minority of lung cancer patients are diagnosed with resectable disease. Therefore, characterization of metastasis-predicting biomarkers in pre-resection small biopsy specimens is urgently needed. Here we report a biomarker consisting of the phosphorylation of the retinoblastoma protein (Rb) on serine 249 combined with elevated p39 expression. This biomarker correlates with epithelial-to-mesenchymal transition traits in non-small cell lung carcinoma (NSCLC) cells. Immunohistochemistry staining of NSCLC tumor microarrays showed that strong phospho-Rb S249 staining positively correlated with tumor grade specifically in the squamous cell carcinoma (SCC) subtype. Strong immunoreactivity for p39 positively correlated with tumor stage, lymph node invasion, and distant metastases, also in SCC. Linear regression analyses showed that the combined scoring for phospho-Rb S249, p39 and E-cadherin in SCC is even more accurate at predicting tumor staging, relative to each score individually. We propose that combined immunohistochemistry staining of NSCLC samples for Rb phosphorylation on S249, p39, and E-cadherin protein expression could aid in the assessment of tumor staging and metastatic potential when tested in small primary tumor biopsies. The intense staining for phospho-Rb S249 that we observed in high grade SCC could also aid in the precise sub-classification of poorly differentiated SCCs.

ROS1 immunohistochemistry among major genotypes of non-small-cell lung cancer.

BACKGROUND: ROS1 gene fusions cause several cancers by constitutively activating the ROS1 tyrosine kinase receptor. ROS1-targeted inhibitor therapy improves survival in the approximately 1% to 2% of patients with lung adenocarcinoma with ROS1 gene fusions. Although fluorescence in situ hybridization (FISH) is the standard diagnostic procedure for detecting ROS1 rearrangements, we studied immunohistochemistry (IHC). MATERIALS AND METHODS: ROS1 IHC was performed on a selected cohort of 33 lung adenocarcinoma whole tissue specimens with alterations in the EGFR (n = 5), KRAS (n = 5), ERBB2 (HER2) (n = 3), ROS1 (n = 6), ALK (n = 5), and RET (n = 3) genes and pan-negative (n = 6) detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and FISH. RESULTS: In the cohort of 33 specimens, both ROS1 gene fusion using RT-PCR and high ROS1 protein expression using IHC were detected in 6 specimens. Of these 6 specimens, 5 were also positive by FISH for ROS1 gene rearrangements. All 27 lung cancer specimens that were negative for ROS1 rearrangements by genetic testing had no to low ROS1 protein expression. CONCLUSION: We have optimized ROS1 IHC and scoring to provide high sensitivity and specificity for detecting ROS1 gene rearrangements in whole tissue. ROS1 IHC could be a practical and cost-effective method to screen for ROS1 gene rearrangements.