Audrey H. Choi

Perioperative chemotherapy for resectable gastric cancer：MAGIC and beyond

Over the last 15 years, there have been major advances in the multimodal treatment of gastric cancer, in large part due to several phase III studies showing the treatment benefits of neoadjuvant and adjuvant chemotherapy and chemoradiation protocols. The objective of this editorial is to review the current high-level evidence supporting the use of chemotherapy, chemoradiation and anti-HER2 agents in both the neoadjuvant and adjuvant settings, as well as to provide a clinical framework for use of this data based on our own institutional protocol for gastric cancer. Major studies reviewed include the SWOG/INT 0116, Medical Research Council Adjuvant Gastric Infusional Chemotherapy (MAGIC), CLASSIC, ACTS-GC, Adjuvant Chemoradiation Therapy in Stomach Cancer (ARTIST) and Trastuzumab for Gastric Cancer trials. Although these studies have demonstrated that multiple approaches in terms of the timing and therapy for gastric cancer are effective, no standard of care is widely accepted and questions regarding the optimal timing of chemotherapy, the benefit of radiotherapy, the minimum required extent of lymphadenectomy and optimal chemotherapy regimen still exist. Protocols from the upcoming ARTIST II, CRITICS, TOPGEAR, Neo-AEGIS and MAGIC-B studies are outlined, and results from these studies will provide critical information regarding optimal timing and treatment regimen. Additionally, the future directions of gastric cancer research predicated on molecular profiling and tailored therapies based on targetable genetic alterations in individual patients tumors are addressed.

From Benchtop to Bedside: A Review of Oncolytic Virotherapy

Oncolytic viruses (OVs) demonstrate the ability to replicate selectively in cancer cells, resulting in antitumor effects by a variety of mechanisms, including direct cell lysis and indirect cell death through immune-mediate host responses. Although the mechanisms of action of OVs are still not fully understood, major advances have been made in our understanding of how OVs function and interact with the host immune system, resulting in the recent FDA approval of the first OV for cancer therapy in the USA. This review provides an overview of the history of OVs, their selectivity for cancer cells, and their multifaceted mechanism of antitumor action, as well as strategies employed to augment selectivity and efficacy of OVs. OVs in combination with standard cancer therapies are also discussed, as well as a review of ongoing human clinical trials.

Epidermal Growth Factor Receptor Signaling to the Mitogen Activated Protein Kinase Pathway Bypasses Ras in Pancreatic Cancer Cells.

Objective Epidermal growth factor (EGF) receptor (EGFR/HER1) is overexpressed in human pancreatic cancers. However, anti-EGFR therapy does not exhibit significant therapeutic activity with oncogenic K-ras mutation. We sought to assess the signaling relationship between EGFR and mutant K-ras, which is commonly detected in pancreatic cancer. Methods Pancreatic cancer cells harboring mutated K-ras were treated with EGF to assess signaling from EGFR to mitogen-activated protein kinase (MAPK) pathway. The role of Ras family of proteins in transducing EGFR signals was assessed using short interfering RNA. Other components of MAPK and PI3K (phosphoinositide 3-kinase) pathways were examined for their roles in EGFR signaling. Results First, EGF signaling in pancreatic cancer cells occurs selectively through HER1. Second, knockdown of all Ras isoforms failed to block EGF-mediated phosphorylation of extracellular signal-regulated kinase (ERK). Inhibition of Raf was observed to partially abrogate ERK phosphorylation, whereas MEK inhibition resulted in complete attenuation of EGF-mediated ERK phosphorylation. Finally, inhibition of phosphoinositide 3-kinase/AKT and CDC42/PAK pathways did not block EGFR signaling. Conclusions Our study results demonstrate that EGFR-mediated signaling in mutant K-ras pancreatic cancer cells does not follow canonical MAPK signaling. Our novel findings suggest the existence of alternate signaling pathways to downstream MAPK in the presence of mutant K-ras.

Accuracy of computed tomography in nodal staging of colon cancer patients

AIM To predict node-positive disease in colon cancer using computed tomography (CT). METHODS American Joint Committee on Cancer stage I-III colon cancer patients who underwent curavtive-intent colectomy between 2007-2010 were identified at a single comprehensive cancer center. All patients had preoperative CT scans with original radiology reports from referring institutions. CT images underwent blinded secondary review by a surgeon and a dedicated abdominal radiologist at our institution to identify pericolonic lymph nodes (LNs). Comparison of outside CT reports to our independent imaging review was performed in order to highlight differences in detection in actual clinical practice. CT reviews were compared with final pathology. Results of the outside radiologist review, secondary radiologist review, and surgeon review were compared with the final pathologic exam to determine sensitivity, specificity, positive and negative predictive values, false positive and negative rates, and accuracy of each review. Exclusion criteria included evidence of metastatic disease on CT, rectal or appendiceal involvement, or absence of accompanying imaging from referring institutions. RESULTS From 2007 to 2010, 64 stageI-III colon cancer patients met the eligibility criteria of our study. The mean age of the cohort was 68 years, and 26 (41%) patients were male and 38 (59%) patients were female. On final pathology, 26 of 64 (40.6%) patients had node-positive (LN+) disease and 38 of 64 (59.4%) patients had node-negative (LN-) disease. Outside radiologic review demonstrated sensitivity of 54% (14 of 26 patients) and specificity of 66% (25 of 38 patients) in predicting LN+ disease, whereas secondary radiologist review demonstrated 88% (23 of 26) sensitivity and 58% (22 of 38) specificity. On surgeon review, sensitivity was 69% (18 of 26) with 66% specificity (25 of 38). Secondary radiology review demonstrated the highest accuracy (70%) and the lowest false negative rate (12%), compared to the surgeon review at 67% accuracy and 31% false negative rate and the outside radiology review at 61% accuracy and 46% false negative rate. CONCLUSION CT LN staging of colon cancer has moderate accuracy, with administration of NCT based on CT potentially resulting in overtreatment. Active search for LN+ may improve sensitivity at the cost of specificity.

CCR9-mediated signaling through β-catenin and identification of a novel CCR9 antagonist

Elevated levels of chemokine receptor CCR9 expression in solid tumors may contribute to poor patient prognosis. In this study, we characterized a novel CCR9‐mediated pathway that promotes pancreatic cancer cell invasion and drug resistance, indicating that CCR9 may play a critical role in cancer progression through activation of β‐catenin. We noted that the CCL25/CCR9 axis in pancreatic cancer cells induced the activation of β‐catenin, which enhanced cell proliferation, invasion, and drug resistance. CCR9‐mediated activation of β‐catenin and the resulting downstream effects were effectively inhibited by blockade of the PI3K/AKT pathway, but not by antagonism of Wnt. Importantly, we discovered that CCR9/CCL25 increased the lethal dose of gemcitabine, suggesting decreased efficacy of anti‐cancer drugs with CCR9 signaling. Through in silico computational modeling, we identified candidate CCR9 antagonists and tested their effects on CCR9/β‐catenin regulation of cell signaling and drug sensitivity. When combined with gemcitabine, it resulted in synergistic cytotoxicity. Our results show that CCR9/β‐catenin signaling enhances pancreatic cancer invasiveness and chemoresistance, and may be a highly novel therapeutic target.

Novel oncolytic chimeric orthopoxvirus causes regression of pancreatic cancer xenografts and exhibits abscopal effect at a single low dose

BackgroundPancreatic ductal adenocarcinoma (PDAC) has been increasing by 0.5% per year in the United States. PDAC portends a dismal prognosis and novel therapies are needed. This study describes the generation and characterization of a novel oncolytic chimeric orthopoxvirus for the treatment of pancreatic cancer.MethodsAfter chimerization and high-throughput screening, CF33 was chosen from 100 new chimeric orthopoxvirus isolates for its ability to kill pancreatic cancer cells. In vitro cytotoxicity was assayed in six pancreatic cancer cell lines. In vivo efficacy and toxicity were evaluated in PANC-1 and MIA PaCa-2 xenograft models.ResultsCF33 caused rapid killing of six pancreatic cancer cells lines in vitro, releasing damage-associated molecular patterns, and regression of PANC-1 injected and non-injected distant xenografts in vivo after a single low intratumoral dose of 103 plaque-forming units. Using luciferase imaging, CF33 was noted to preferentially replicate in tumors which corresponds to the low viral titers found in solid organs.ConclusionThe low dose of CF33 required to treat pancreatic cancer in this preclinical study may ease the manufacturing and dosing challenges currently facing oncolytic viral therapy.

Endogenous Akt Activity Promotes Virus Entry and Predicts Efficacy of Novel Chimeric Orthopoxvirus in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with high recurrence rate and poor prognosis. Here, we describe a novel, chimeric orthopoxvirus (CF33) that efficiently kills TNBC. Cytotoxicity was assayed in vitro in four TNBC cell lines. Viral replication was examined through standard plaque assay. Two orthotopic TNBC xenograft models were generated in athymic nude mice and were injected with CF33 intratumorally. CF33 was effective in vitro with potent cytotoxicity and efficient intracellular replication observed in TNBC lines with phosphatidylinositol 3-kinase (PI3K)/Akt pathway mutations that resulted in endogenous phospho-Akt (p-Akt) activity (BT549, Hs578T, and MDA-MB-468). Relative resistance to CF33 by wild-type PI3K/Akt pathway cell line MDA-MB-231 was overcome using higher MOI. The virus was effective in vivo with significant tumor size reduction in both xenograft models. Mechanistically, CF33 appears to share similar properties to vaccinia virus with respect to Akt-mediated and low-pH-mediated viral entry. In summary, CF33 demonstrated potent antitumoral effect in vitro and in vivo, with the most potent effect predicted by the presence of endogenous Akt activity in the TNBC cell line. Further investigation of its mechanism of action as well as genetic modifications to enhance its natural viral tropism are warranted for preclinical development.

A Novel Oncolytic Chimeric Orthopoxvirus Encoding Luciferase Enables Real-Time View of Colorectal Cancer Cell Infection

This study hypothesizes that a novel oncolytic chimeric orthopoxvirus CF33-Fluc is imageable and targets colorectal cancer cells (CRCs). A novel chimeric orthopoxvirus (CF33) was constructed. The thymidine kinase locus was replaced with firefly luciferase (Fluc) to yield a recombinant virus—CF33-Fluc. In vitro cytotoxicity and viral replication assays were performed. In vivo CRC flank xenografts received single doses of intratumoral or intravenous CF33-Fluc. Viral biodistribution was analyzed via luciferase imaging and organ titers. CF33-Fluc infects, replicates in, and kills CRCs in vitro in a dose-dependent manner. CF33 has superior secretion of extracellular-enveloped virus versus all but one parental strain. Rapid tumor regression or stabilization occurred in vivo at a low dose over a short time period, regardless of the viral delivery method in the HCT-116 colorectal tumor xenograft model. Rapid luciferase expression in virus-infected tumor cells was associated with treatment response. CRC death occurs via necroptotic pathways. CF33-Fluc replicates in and kills colorectal cancer cells in vitro and in vivo regardless of delivery method. Expression of luciferase enables real-time tracking of viral replication. Despite the chimerism, CRC death occurs via standard poxvirus-induced mechanisms. Further studies are warranted in immunocompetent models.

Novel chimeric parapoxvirus CF189 as an oncolytic immunotherapy in triple-negative breast cancer

Background Triple‐negative breast cancer is an aggressive subtype of breast cancer with high recurrence rate and poor prognosis. Here we describe a novel, genetically engineered parapoxvirus that efficiently kills triple‐negative breast cancer. Methods A novel chimeric parapoxvirus (CF189) was generated via homologous recombination and identified through high‐throughput screening. Cytotoxicity was assayed in vitro in 4 triple‐negative breast cancer cell lines. Viral replication was examined through standard plaque assay. Orthotopic triple‐negative breast cancer xenografts were generated by MDA‐MB‐468 implantation into the 2nd and 4th mammary fat pads of athymic nude mice and treated with the virus. Results Chimeric parapoxvirus (CF189) demonstrated dose‐dependent cytotoxicity at low multiplicity of infection, with > 80% cell death 6 days after treatment. Significant reductions in tumor size were observed 2 weeks after intratumoral injection at doses as low as 103 plaque‐forming units (PFU) compared with control (P < 0.01). In addition, abscopal effect (shrinkage of noninjected remote tumors) was clearly demonstrated. Conclusion Chimeric parapoxvirus (CF189) demonstrated efficient cytotoxicity in vitro and potent antitumor effect in vivo at doses as low as 103 PFU. These are data encouraging of clinical development for this highly potent agent against triple‐negative breast cancer.

Abstract 2775: Characterization of transcriptional and epigenetic signatures of benign thyroid adenomas: Can we improve preoperative diagnosis of thyroid nodules

Introduction: It has been estimated that as many as 50,000 patients in the United States receive unnecessary thyroidectomies due to the inability to distinguish benign thyroid nodules from malignant ones. Up to 30% of fine needle aspirates performed for thyroid nodules diagnosis are indeterminate due to overlapping cytological features between benign and malignant nodules. At present, commercially-available diagnostic tests for thyroid nodules are based on the molecular differences observed between thyroid cancer compared to normal thyroid tissue. However, the molecular signature of benign thyroid nodules is neither well-characterized nor included in currently available diagnostic panels. The objective of this study was to determine whether thyroid adenomas (TA) are distinct from normal thyroid tissue and papillary thyroid cancer (PTC). Methods: Whole transcriptome analysis was used to assess differences in transcriptional activity in 9 TA and 12 PTC tissue pairs (with matched normal adjacent thyroid tissue from the same patients). In order to evaluate epigenetic alterations associated with TA development, we used reduced representation bisulfite sequencing (RRBS) in 114 thyroid specimens (40 PTC, 28 TA and 46 matching adjacent thyroid tissues). This approach provides single base resolution of DNA methylation genome wide. Results: According to our data, transcriptome activity divided analyzed specimens into three separate groups: PTC, TA and adjacent thyroid tissues. TA demonstrated a unique transcriptional pattern, distinct from both normal adjacent thyroid tissue and PTC. Similar results were obtained by analysis of epigenetic alterations in these tissues. According to the clustering analysis of DNA methylation patterns, the majority (18 of 28) of benign nodules forms a separate cluster, distinct from adjacent normal thyroid and PTC tissue clusters. Within this group, 14 of 28 TA demonstrated a distinct DNA methylation signature associated with TA-specific hypermethylation. In fact, only 4 of 28 TA demonstrated a DNA methylation signature similar to normal thyroid tissue, suggesting that the majority of TA is not equivalent to normal thyroid. Conclusion: According to whole transcriptome analysis and genome wide analysis of DNA methylation, TA is frequently associated with specific transcriptional and DNA methylation signatures compared to normal thyroid tissue and PTC. These data indicate that the majority of thyroid adenomas are associated with a unique molecular pathway that is distinct from PTC development. Use of the adenoma-specific molecular signature can be an essential factor in the improvement of PTC diagnostic panels, helping to reduce unnecessary thyroidectomies. Citation Format: Audrey H. Choi, Ryan Lew, Michael O’Leary, Yuman Fong, John H. Yim, Maria A. Hahn. Characterization of transcriptional and epigenetic signatures of benign thyroid adenomas: Can we improve preoperative diagnosis of thyroid nodules. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2775.