PD-L1 Expression Is Significantly Associated with Tumor Mutation Burden and Microsatellite Instability Score.

Programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC), microsatellite instability (MSI), and tumor mutation burden (TMB) have been proposed as a predictive biomarker to predict response to immune checkpoint blockade (ICB). We aimed to find the relationship of PD-L1 IHC to TMB and MSI using a comprehensive cancer panel assay (CCPA) with >500 genes in advanced cancer patients. CCPA results from 588 archived tissue samples were analyzed for TMB and MSI. In seven samples, whole exome sequencing confirmed TMB with Pearson's correlation coefficient of 0.972 and all MSI-high cases were validated by pentaplex PCR. Association of TMB and MSI with their corresponding PD-L1 IHC was analyzed. The median TMB value of 588 cases was 8.25 mutations (mut)/Mb (range 0-426.8) with different distributions among the tumor types, with high proportions of high-TMB (>10mut/Mb) in tumors from melanoma, colorectal, gastric, and biliary tract. The TMB values significantly correlated with PD-L1 expression, and this correlation was prominent in gastric and biliary tract cancers. Moreover, the MSI score, the proportion of unstable MSI sites to total assessed MSI sites, showed a significant correlation with the TMB values and PD-L1 scores. This study demonstrates that PD-L1 expression is significantly associated with TMB and MSI score and this correlation depends on the location of the primary tumor.

Patient-Derived Xenograft Models of Epithelial Ovarian Cancer for Preclinical Studies.

PURPOSE: Patient-derived tumor xenografts (PDXs) can provide more reliable information about tumor biology than cell line models. We developed PDXs for epithelial ovarian cancer (EOC) that have histopathologic and genetic similarities to the primary patient tissues and evaluated their potential for use as a platform for translational EOC research. MATERIALS AND METHODS: We successfully established PDXs by subrenal capsule implantation of primary EOC tissues into female BALB/C-nude mice. The rate of successful PDX engraftment was 48.8% (22/45 cases). Hematoxylin and eosin staining and short tandem repeat analysis showed histopathological and genetic similarity between the PDX and primary patient tissues. RESULTS: Patients whose tumors were successfully engrafted in mice had significantly inferior overall survival when compared with those whose tumors failed to engraft (p=0.040). In preclinical tests of this model, we found that paclitaxel-carboplatin combination chemotherapy significantly deceased tumor weight in PDXs compared with the control treatment (p=0.013). Moreover, erlotinib treatment significantly decreased tumor weight in epidermal growth factor receptor-overexpressing PDX with clear cell histology (p=0.023). CONCLUSION: PDXs for EOC with histopathological and genetic stability can be efficiently developed by subrenal capsule implantation and have the potential to provide a promising platform for future translational research and precision medicine for EOC.

ALK, ROS1 and RET rearrangements in lung squamous cell carcinoma are very rare.

OBJECTIVES: Chromosomal rearrangements of ALK and ROS1 genes in non-small cell lung carcinoma (NSCLC) define a molecular subgroup of lung adenocarcinoma (ADC) that is amenable to targeted therapy with tyrosine kinase inhibitors (TKIs) crizotinib. Emerging clinical studies have demonstrated that patients with RET-rearranged NSCLC may also benefit from existing RET TKIs, including cabozantinib and vandetanib. However, the reported cases of lung squamous cell carcinomas (SCC) harboring gene rearrangements have been detected via fluorescence in situ hybridization (FISH) or immunohistochemistry (IHC) from materials such as biopsy or resection. Fusion events identified in lung SCC raise the question of whether this histologic subtype should also be evaluated for merit molecular testing. This work was undertaken to study the prevalence of lung SCC harboring ALK, ROS1, and RET translocations. MATERIALS AND METHODS: Squamous cell carcinomas were confirmed using both histological examination by pathologists and immunohistochemistry analysis with positive staining of P63 and CK5/6 combined with negative CK7 and TTF-1 staining. 214 samples from surgically resected patient tissues were used to search for ALK, ROS1, and RET rearrangements by a NanoString analysis method. Fusion events were detected in a single-tube, multiplex assay system that relied on a complementary strategy of interrogation of 3' gene overexpression and detection of specific fusion transcript variants. RESULTS AND CONCLUSION: ALK, ROS1 or RET gene rearrangements appeared 0 times out of 214 cases of lung SCC. Our data revealed that these fusions may be very rare in lung squamous cancer. The molecular screening strategy should therefore be focused on lung adenocarcinoma as the current National Comprehensive Cancer Network (NCCN) guideline recommends.

EGFR mutation testing in patients with advanced non-small cell lung cancer: a comprehensive evaluation of real-world practice in an East Asian tertiary hospital.

INTRODUCTION: Guidelines for management of non-small cell lung cancer (NSCLC) strongly recommend EGFR mutation testing. These recommendations are particularly relevant in Asians that have higher EGFR mutation prevalence. This study aims to explore current testing practices, logistics of testing, types of EGFR mutation, and prevalence of EGFR mutations in patients with advanced NSCLC in a large comprehensive cancer center in Korea. METHODS: Our retrospective cohort included 1,503 NSCLC patients aged ≥18 years, with stage IIIB/IV disease, who attended the Samsung Medical Center in Seoul, Korea, from January 2007 through July 2010. Trained oncology nurses reviewed and abstracted data from electronic medical records. RESULTS: This cohort had a mean age (SD) of 59.6 (11.1) years, 62.7% were males, and 52.9% never-smokers. The most common NSCLC histological types were adenocarcinoma (70.5%) and squamous cell carcinoma (18.0%). Overall, 39.5% of patients were tested for EGFR mutations. The proportion of patients undergoing EGFR testing during January 2007 through July 2008, August 2008 through September 2009, and October 2009 through July 2010 were 23.3%, 38.3%, and 63.5%, respectively (P<0.001). The median time elapsed between cancer diagnoses and receiving EGFR testing results was 21 days. EGFR testing was most frequently ordered by oncologists (57.7%), pulmonologists (31.9%), and thoracic surgeons (6.6%). EGFR testing was more commonly requested for women, younger patients, stage IV disease, non-smokers, and adenocarcinoma histology. Of 586 cases successfully tested for EGFR mutations, 209 (35.7%) were positive, including 118 cases with exon 19 deletions and 62 with L858R mutations. EGFR mutation positive patients were more likely to be female, never-smokers, never-drinkers and to have adenocarcinoma. CONCLUSIONS: In a large cancer center in Korea, the proportion of EGFR testing increased from 2007 through 2010. The high frequency of EGFR mutation positive cases warrants the need for generalized testing in Asian NSCLC patients.

Multiplexed gene expression and fusion transcript analysis to detect ALK fusions in lung cancer.

Anaplastic lymphoma kinase gene (ALK) fusions have been identified in approximately 5% of non-small-cell lung carcinomas (NSCLCs) and define a distinct subpopulation of patients with lung cancer who are highly responsive to ALK kinase inhibitors, such as crizotinib. Because of this profound therapeutic implication, the latest National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology recommend upfront ALK screening for all patients with NSCLC. The Food and Drug Administration-approved companion diagnostic test (ie, fluorescence in situ hybridization) for identification of ALK-positive patients, however, is complex and has considerable limitations in terms of cost and throughput, making it difficult to screen many patients. To explore alternative screening modalities for detecting ALK fusions, we designed a combination of two transcript-based assays to detect for presence or absence of ALK fusions using NanoString's nCounter technology. By using this combined gene expression and ALK fusion detection strategy, we developed a multiplexed assay with a quantitative scoring modality that is highly sensitive, reproducible, and capable of detecting low-abundant ALK fusion transcripts, even in samples with a low tumor cell content. In 66 archival NSCLC samples, our results were highly concordant to prior results obtained by fluorescence in situ hybridization and IHC. Our assay offers a cost-effective, easy-to-perform, high-throughput, and FFPE-compatible screening alternative for detection of ALK fusions.