Trastuzumab, has played a major role in improving treatment outcomes in HER-2 positive gastric cancer. However, once there is disease progression there is a paucity of evidence for second line therapy. Patient-derived xenografts (PDXs) in combination with liquid biopsies can help guide individual therapeutic decisions and have now started to be studied. In the present case we established a PDX model from a metastatic HER-2+ gastric cancer patient and after the first engraftment passage we performed a mouse clinical trial to test T-DM1 as an alternative therapy for the patient. The PDX tumor response served as a guide to administer T-DM1 therapy to the patient who responded to treatment before relapsing 6 months later. Throughout out the clinical follow up of the patient, ctDNA levels of HER-2 copy number and a PIK3CA mutation were monitored and we found their correlation with drug response and disease progression to outperform that of CEA levels. This study highlights the utility of applying precision medicine tools combining PDX models to guide therapy with circulating tumor DNA (ctDNA) to monitor treatment response and disease progression.

Mesothelin (MSLN) is a cancer-specific antigen that is differentially expressed in many human cancers, including malignant mesothelioma and pancreatic, ovarian, and lung adenocarcinomas. The MSLN gene encodes a 71 kD precursor protein, that is reportedly cleaved by the intracellular protease furin to produce a 31 kD N-terminal fragment called megakaryocyte potentiating factor (MPF) and mature 40 kD MSLN C-terminal fragment. Mature MSLN is localized to the cell surface by a GPI-linkage. We synthesized a series of mutant MSLN constructs containing sequence modifications predicted to disrupt the canonical signaling sequences for furin cleavage and GPI-linkage. These constructs were then expressed in a MSLN knock-out pancreatic cancer cell line. We used flow cytometry to detect cell surface MSLN expression and immunoblotting for MSLN proteins to assess the effect of mutation. We expected that a 23aa C-terminal truncation that removed a predicted hydrophobic signaling sequence for GPI-linkage would eliminate plasma membrane insertion of MSLN. However, this truncation did not suppress cell surface expression. A deeper 31aa truncation which eliminated two potential anchoring sites at Ser599 and Ser606 was required to successfully eliminate surface expression. We are currently evaluating the growth of this pancreatic cancer cell line expressing GPI-truncated soluble MSLN in vitro and in vivo. Our results suggest that MSLN may have an alternate means for membrane insertion besides GPI-linkage. For the panel of furin site mutants, non-conservative mutations were made to disrupt the reported consensus recognition motif for furin 290-RPRFRR-295 (R290H, R292Q, RR294-5GG) or the entire motif region was deleted (289_315del). Mutants were also made to disrupt the putative furin cleavage site (R286A) and neighboring basic residues that were potential protease cleavage sites (R282A, K306Q, K307Q). These furin site mutants were expected to eliminate cleavage of the 71 kD precursor protein to 40 kD mature MSLN. We found that all mutants did increase levels of precursor but did not ablate formation of mature MSLN. Similarly, expression of WT full-length MSLN into the LoVo cell line, which lacks furin activity, still resulted in formation of 40 kD mature MSLN predominately. In conclusion, we found that precursor processing to mature MSLN still took place despite extensive mutation of the putative furin cleavage site and in the absence of active furin. These results suggest that additional proteases besides furin can perform MSLN precursor cleavage. Citation Format: Sarah Mary Joseph, Leela Rani Avula, Xianyu Zhang, Christine Campo Alewine. The molecular dissection of pro-tumorigenic activity of mesothelin in pancreatic cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1449.

Background. Scrotal swelling is a rare complication of acute pancreatitis with few reported cases in the literature. In this case report, we present a 59-year-old male with hydrochlorothiazide induced pancreatitis who developed scrotal swelling. Case Presentation. A 59-year-old male presented to the emergency department with sharp epigastric abdominal pain that radiated to the back and chest. On physical examination, he had abdominal tenderness and distention with hypoactive bowel sounds. Computed tomography (CT) scan of the abdomen showed acute pancreatitis. The patient's condition deteriorated and he was admitted to the intensive care unit (ICU). After he improved and was transferred out of the ICU, the patient developed swelling of the scrotum and penis. Ultrasound (US) of the scrotum showed large hydrocele bilaterally with no varicoceles or testicular masses. Good blood flow was observed for both testicles. The swelling diminished over the next eight days with the addition of Lasix and the patient was discharged home in stable condition. Conclusion. Scrotal swelling is a rare complication of acute pancreatitis. It usually resolves spontaneously with conservative medical management such as diuretics and elevation of the legs.

Pancreatic cancer is one of the most lethal carcinomas in the United States. In accord with the American Cancer Society pancreatic cancer is anticipated to move from the third to the second leading cause of deaths in the United States by 2020. Although the standard treatment for advanced pancreatic cancer is gemcitabine (GEM), the response rate is less than 20%. Chemoresistance is a hallmark of this cancer, and modulation of drug transporters expression has been shown to increase cancer drug efficacy. Studies have shown that human equilibrative nucleoside transporters (hENTs) expression patterns may predict GEM treatment efficacy. This study investigated whether or not GEM in combination with metformin (MET) or indole-3-carbinol (I3C) increases cytotoxicity and modulates hENT1 and hENT4. Pancreatic cancer cells from males and females were treated for 24 or 72h with GEM and/or MET or I3C. Cell viability, drug interactions, and protein and mRNA expression levels of hENTs were assessed. Treatment with GEM and/or MET or I3C showed cell line specific reductions in pancreatic cancer cell proliferation, and modulation of hENT1 and hENT4 expression. Response to GEM and MET/I3C may be dependent upon the genetic profile of the tumor and the level of expression of a specific transporter. The sensitivity of GEM could depend on the method of treatment, whether cells were pre-treated with MET or I3C, which studies, including our own, have showed that pre-treatment with I3C increased upregulation of hENT1 expression in pancreatic cancer cell lines.Keywords: pancreatic cancer; gemcitabine; indole-3-carbinol; metformin; human equilibrative nucleoside transporters

Hemorrhagic pericardial effusion with associated cardiac tamponade as a de novo sign of malignancy is seen in about 2% of patients.1 Consequently, cardiac tamponade is an oncologic emergency and considered a unique presentation of a malignancy.2 Cancer emergency is defined as an acute condition that is caused directly by the cancer itself or its treatment and requires intervention to avoid death or significant morbidity.3 The mechanism by which cardiac tamponade is classified as a life-threatening emergency stems from its impairment of right ventricular filling, resulting in ventricular diastolic collapse and decreased cardiac output, which can ultimately lead to death.4 We describe the case of a previously healthy woman in her late 40s who was a nonsmoker with no previous risk factors and who presented with a large pericardial effusion and bilateral pulmonary emboli. She was diagnosed with metastatic epidermal growth factor receptor-positive (EGFR-positive) adenocarcinoma of the lung. This case highlights an oncologic emergency as a de novo presentation of malignancy.