Nasopharyngeal carcinoma patient-derived xenograft mouse models reveal potential drugs targeting cell cycle, mTOR, and autophagy pathways.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is associated with Epstein-Barr virus (EBV) infection. To test preclinical NPC drugs, we established two patient-derived xenograft (PDX) mouse models, EBV-positive PDX-B13 and EBV-negative PDX-Li41, for drug screening. METHODS: Based on next generation sequencing (NGS) studies, PDX-B13 had CCND1 copy number (CN) gain but CDKN2A CN loss, whereas PDX-Li41 had CDKN2A and RB1 CN loss, TSC1 (negative regulator of mTOR) frameshift deletion mutation, and increased activation of mTOR, a serine/threonine kinase that governs metabolism, autophagy, and apoptosis. Increased mTOR was also associated with poor NPC prognosis. RESULTS: Everolimus, an mTOR inhibitor, suppressed tumor growth in the two PDX NPC models and had an additive antitumor effect with palbociclib, a CDK4/6 inhibitor. PDX tumors treated with various drugs or untreated were subjected to RNA sequencing, transcriptome profile analysis, and selective Western blotting to understand the interactions between these drugs and gene expression profiles. Palbociclib also suppressed EB viral nuclear antigen (EBNA1) expression in PDX-B13. Everolimus together with autophagy inhibitor, hydroxychloroquine, had additive anti-tumor effect on PDX-B13 tumor. Immunohistochemistry revealed that high mTOR levels were correlated with poor overall survival in patients with metastatic NPC (N = 90). CONCLUSIONS: High mTOR levels are a poor prognostic factor in NPC, and cell cycle, mTOR and autophagy pathways may serve as therapeutic targets in NPC. In addition, PDX models can be used for efficiently testing potential NPC drugs.

Combination of Epithelial Growth Factor Receptor Blockers and CDK4/6 Inhibitor for Nasopharyngeal Carcinoma Treatment.

BACKGROUND: Nasopharyngeal carcinoma (NPC) involves host genetics, environmental and viral factors. In clinical observations, patients of young and old ages were found to have higher recurrence and metastatic rates. METHODS: Cytokine array was employed to screen druggable target(s). The candidate target(s) were confirmed through patient-derived xenografts (PDXs) and a new EBV-positive cell line, NPC-B13. RESULTS: Overexpression of epithelial growth factor (EGF) and EGF receptor (EGFR) was detected in young patients than in older patients. The growth of NPC PDX tumors and cell lines was inhibited by EGFR inhibitors (EGFRi) cetuximab and afatinib when used separately or in combination with the cell cycle blocker palbociclib. Western blot analysis of these drug-treated PDXs demonstrated that the blockade of the EGF signaling pathway was associated with a decrease in the p-EGFR level and reduction in PDX tumor size. RNA sequencing results of PDX tumors elucidated that cell cycle-related pathways were suppressed in response to drug treatments. High EGFR expression (IHC score ≥ grade 3) was correlated with poor survival in metastatic patients (p = 0.008). CONCLUSIONS: Our results provide encouraging preliminary data related to the combination treatment of EGFRi and palbociclib in patients with NPC.

Integrated genomic analyses in PDX model reveal a cyclin-dependent kinase inhibitor Palbociclib as a novel candidate drug for nasopharyngeal carcinoma.

BACKGROUND: Patient-derived xenograft (PDX) tumor model has become a new approach in identifying druggable tumor mutations, screening and evaluating personalized cancer drugs based on the mutated targets. METHODS: We established five nasopharyngeal carcinoma (NPC) PDXs in mouse model. Subsequently, whole-exome sequencing (WES) and genomic mutation analyses were performed to search for genetic alterations for new drug targets. Potential drugs were applied in two NPC PDX mice model to assess their anti-cancer activities. RNA sequencing and transcriptomic analysis were performed in one NPC PDX mice to correlate with the efficacy of the anti-cancer drugs. RESULTS: A relative high incident rate of copy number variations (CNVs) of cell cycle-associated genes. Among the five NPC-PDXs, three had cyclin D1 (CCND1) amplification while four had cyclin-dependent kinase inhibitor CDKN2A deletion. Furthermore, CCND1 overexpression was observed in > 90% FFPE clinical metastatic NPC tumors (87/91) and was associated with poor outcomes. CNV analysis disclosed that plasma CCND1/CDKN2A ratio is correlated with EBV DNA load in NPC patients' plasma and could serve as a screening test to select potential CDK4/6 inhibitor treatment candidates. Based on our NPC PDX model and RNA sequencing, Palbociclib, a cyclin-dependent kinase inhibitor, proved to have anti-tumor effects by inducing G1 arrest. One NPC patient with liver metastatic was treated with Palbociclib, had stable disease response and a drop in Epstein Barr virus (EBV) EBV titer. CONCLUSIONS: Our integrated information of sequencing-based genomic studies and tumor transcriptomes with drug treatment in NPC-PDX models provided guidelines for personalized precision treatments and revealed a cyclin-dependent kinase inhibitor Palbociclib as a novel candidate drug for NPC.

Correlation between overall survival and differential plasma and tissue tumor marker expression in nasopharyngeal carcinoma patients with different sites of organ metastasis.

Differential overall survival of nasopharyngeal carcinoma (NPC) with different organ site metastases has been documented. Here, we attempted to determine the underlying mechanisms by assessing plasma and tumor tissue markers in relation to patient survival. Pretreatment plasma Epstein-Barr virus (EBV) DNA concentrations, cytokines and tissue macrophages, proliferation and apoptosis markers were determined in 178 patients with metastatic NPC. The median overall survival (OS) was 19 months. Patients with single organ metastases had better outcomes than those with multiple organ metastases (median OS: 26 months vs. 16 months), with statistical significance. Among the single organ involvement cases, patients with lung metastasis only showed longer survival than those with bone or liver involvement (median OS: 50 months vs. 21 months vs. 18 months; P < 0.001). Pretreatment plasma EBV DNA concentrations were lower in patients with lung metastasis than bone or liver metastasis among single organ site groups. Plasma interferon-γ-inducible protein-10 (IP-10) and monocyte chemotactic protein-1 (MCP-1) expression levels were correlated with differential single organ site metastasis OS and EBV DNA load. Liver metastatic tissue had higher density of infiltrating macrophages and proliferative index than the lung metastatic group. Low pretreatment plasma EBV DNA load, expression of cytokines, such as IP-10 and MCP-1, tissue macrophage infiltration, and proliferative index may contribute to the differences in overall survival.

Application of a patient-derived xenograft model in cytolytic viral activation therapy for nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is an Epstein Barr virus (EBV)-related malignancy in which the tumor microenvironment plays a pivotal role in tumor progression. Here, we developed two patient-derived xenograft (PDX) mouse lines from engrafted NPC metastatic tumors. Positive staining for EBV-encoded small RNAs confirmed that these tumors harbored EBV, and gene expression profile analyses further showed that the PDX was highly similar to the primary parent tumor. In vivo drug screening using the PDX system demonstrated that gemcitabine had the best antitumor effect among the tested drugs. The donor of this PDX also showed excellent responsiveness to gemcitabine treatment. The combination of gemcitabine and valproic acid exerted synergistic antitumor effects. Further addition of ganciclovir to this two-drug combination regimen enhanced cytolytic viral activation, yielding the best antitumor response among tested regimens. Treatment with this three-drug combination regimen decreased plasma EBV-DNA load, tumor viral concentration, and the number of viable tumor cells to a greater extent than the two-drug gemcitabine and valproic acid combination. These results highlight the value of PDX models in the development of EBV-targeted strategies to treat NPC.