Citations

Pazopanib is a vascular endothelial growth factor receptor tyrosine kinase inhibitor (VEGFR TKI) that inhibits the vascular endothelial growth factor receptor A pathway and has the potential to cause ischaemic bowel changes, including perforation. Here we report a case of a 51-year-old man with large, metastatic, retroperitoneal leiomyosarcoma that developed a tumour-bowel fistula after 4 weeks of pazopanib therapy. He presented to the emergency department with sepsis and 1-week history of worsening fever, chills, nausea and diarrhoea. Abdominal CT findings of mesenteric and portal vein gas, commonly found in mesenteric ischaemia and VEGFR modulator-induced bowel toxicity, provided evidence for the causal relation. Unfortunately, the case was not amenable to surgery and patient succumbed to the illness.

Abstract Background: A challenge for novel therapeutic strategies will be the fine tuning of intracellular reactive oxygen species (ROS) signaling in order to effectively deprive cells from ROS-induced tumor promoting events and subsequent tipping the balance to ROS-induced apoptotic signaling. ROS plays a critical role in regulation of the pro-survival receptor tyrosine kinase (RTK) signaling pathways in human cancers. Studies have identified mitochondrial metabolism as the key source for abundant ROS in chronic lymphocytic leukemia (CLL). Unlike in other malignant cells, increased oxidative phosphorylation but not increased aerobic glycolysis has been found in CLL B-cells. While we have detected constitutively phosphorylated/active RTKs like Axl in CLL B-cells, the mechanism of activation remains largely undefined. Here we report that (i) elevated ROS activates the Axl signaling pathway in CLL B-cells and, (ii) mechanism of increased ROS accumulation in the leukemic B-cells. Methods: CLL B- and normal B-cells were purified from peripheral blood of previously untreated CLL patients and normal healthy individuals, respectively using a RossetteSep B-Cell enrichment kit. CLL B-cells were exposed to H2O2 for 5 min and cell lysates were analyzed for activation of RTKs including Axl by immunoprecipitation/Western blots. We also examined expression status of SIRT3, acetylated-superoxide dismutase (SOD)2 and catalase in CLL B-cells by Western blots. Catalase mRNA levels in CLL B-/normal B-cells were determined by qRT-PCR. In some experiments, genomic DNA was isolated from CLL B-/normal B-cells for catalase promoter methylation studies. Finally, accumulation of O2‾ and H2O2 in CLL B- and normal B-cells were measured by flow cytometry after treating the cells withdihydroethidium (DHE) and dichlorohydrofluorescein diacetate (DCFDA), respectively. Results: We found that enforced induction of ROS significantly increases tyrosine phosphorylation levels on multiple cellular proteins in CLL B-cells (Fig. 1). Further analysis finds that increased ROS activates Axl and its downstream targets AKT/Erk1/2 MAPK and the fibroblast growth factor receptor (FGFR) which we recently defined as a downstream target of Axl; while ROS accumulation did not show any significant effect on other RTKs, cMET or IGFR1, in CLL B-cells. Interestingly, the histone deacetylase SIRT3 which activates mitochondrial SOD2 via deacetylation, we found, was overexpressed in CLL B-cells as compared to normal B-cells indicating more efficient conversion of O2‾ into H2O2 in the leukemic B-cells (Fig. 2). However expression of catalase, which converts H2O2 into O2 and H2O, was reduced significantly in CLL B-cells as compared to normal B-cells both at mRNA and protein levels. To delineate the mechanism of reduced expression of catalase in CLL B-cells we studied the human catalase promoter region for potential methylation sites using the method of HpaII restriction enzyme digestion where HpaII is unable to cut DNA (CCGG site) when the internal cytosine is methylated. Initial findings from this approach suggest that while the catalase gene promoter in CLL B-cells may contain methylated cytosines, the catalase gene in normal B-cells may not confer methylation in the promoter region. Next, genomic DNA from CLL B-cells (n=10) and normal B-cells (n=6) was subjected to bisulfite treatment, followed by PCR amplification and sequencing. This approach revealed no significant promoter methylation of the catalase gene in normal B-cells, while moderate to heavily methylated promoter of the catalase gene was detected in CLL B-cells from majority of CLL patients (9 of 10). Further studies are in progress to examine catalase promoter methylation status in a larger cohort of CLL patients and its association with H2O2 accumulation, RTK phosphorylation and risk-factors. Indeed, flow cytometric analysis finds lower levels of O2‾ but accumulation of H2O2 in CLL B-cells as compared to normal B-cells. Taken together, these findings suggest that although SOD2 remains highly active, increased accumulation of H2O2 may occur in CLL B-cells due to epigenetic silencing of the catalase gene. Conclusion: These observations may explain, at least in part, the expression of constitutively active Axl signaling pathway in CLL B-cells that plays a role in CLL B cell survival and may account for the prolonged survival and/or apoptotic resistance of the leukemic B-cells. Disclosures No relevant conflicts of interest to declare.

TPS504 Background: Patients with high-risk MIBC have a poor prognosis. Radical cystectomy remains the standard treatment. Yet despite substantial improvements in surgical techniques, mortality from metastatic recurrence remains high. A large number of MIBC patients are ineligible for cisplatin-based chemotherapy or have persistent muscle-invasive disease despite neoadjuvant chemotherapy (NAC). Pembrolizumab, a PD-1 inhibitor, has demonstrated significant activity and is FDA-approved for patients with advanced/chemotherapy-refractory metastatic urothelial carcinoma. We hypothesize that pembrolizumab given post-cystectomy will improve overall survival (OS) and disease-free survival (DFS) in patients with high-risk MIBC. Methods: Patients must have histologically confirmed muscle-invasive urothelial carcinoma of the bladder or upper tract, have received NAC and have ≥ pT2 and/or pN+ at surgery or be cisplatin-ineligible and have ≥ pT3 and/or pN+ at surgery or have declined adjuvant cisplatin-based therapy and have ≥ pT3 and/or pN+ at surgery. Surgery could be radical cystectomy, nephrectomy, or ureterectomy. Patients are stratified by pathologic stage, central PD-L1 status, and prior NAC. Patients are randomized to receive pembrolizumab 240 mg every 3 weeks for 1 year, or observation. The dual primary objectives are to determine DFS and OS. Secondary objectives are to determine DFS and OS in PD-L1-positive and -negative patients and assess safety. Correlative objectives are to determine whether 12 immune gene signatures, tumor molecular subtypes, diversity of T-cell receptor (TCR) clonotypes, persistence of TCR clonotypes, tumor and neoantigen burden, HLA subtypes, and plasma HGF and VEGF levels with IL-10 and IL-17 are associated with OS and DFS. Quality of Life Correlative objectives are to compare health-related quality of life as assessed by the EORTC QLQ-C30. Clinical trial information: NCT03244384.

Postobstructive pulmonary edema (POPE) also known as negative pressure pulmonary edema (NPPE) is an underdiagnosed entity in clinical practice and can lead to life-threatening hypoxemia. A 64-year-old male patient’s perioperative course was complicated by acute hypoxemic respiratory failure, after extubation following general anesthesia, following the excision of the right vocal cord papilloma. His chest X-ray showed features of pulmonary edema, EKG showed dynamic ST-T changes in the lateral leads, and echocardiography showed evidence of regional motion abnormalities. His coronaries were normal on the immediate angiogram. He was managed with lung protective mechanical ventilation strategy, diuretics, and fluid restriction. His respiratory status improved, and trachea was extubated after 10 hours of intensive care unit (ICU) stay. The case illustrates the various differentials of immediate postoperative flash pulmonary edema and ensuing appropriate management strategy.

Infections caused by the Bartonella species are responsible for the human diseases collectively called ‘bartonellosis’. The clinically important human infections are mostly caused by the three species (eg, B. bacilliformis, B. quintana and B. henselae) of Bartonella out of the many progressively increasing identified species. Bartonella henselae transmitted by the arthropod vector, fleas, after cat bite is responsible for the rare multisystem cat scratch disease in humans. We present an extremely rare case of B. henselae contracted presumably through a red ant bite. The patient had a prolonged hospital stay for persistent encephalopathy due to delay in diagnosis and initiation of antimicrobial therapy. His hospital course was complicated by two episodes of pulseless electrical activity cardiac arrest related to pulmonary embolism. However, he recovered to his baseline status in the hospital with timely administration of systemic anticoagulation and antimicrobials. He was discharged home with no neurological deficits.

A 54-year-old man presented to the emergency department with acute left-sided chest pain and left upper quadrant abdominal pain. He had a significant history of squamous cell carcinoma of the lung previously treated with right pneumonectomy who ; is currently receiving adjuvant chemotherapy with cisplatin. Physical examination was remarkable for tachycardia, hypertension and mild abdominal tenderness. CT angiography revealed an aortic mural thrombus in the ascending aorta and aortic arch without dissection, aneurysm or tortuosity of the aorta. In addition, an infarction of the inferior spleen was reported. Given the high risk of surgery for this patient, he was treated conservatively with esmolol and heparin infusion. His subsequent hospital course was uneventful, and he was successfully discharged on enoxaparin therapy that was successively bridged to rivaroxaban treatment. Follow-up transesophageal echocardiography and CT angiography at one month showed no thrombus in the aorta.

475 Background: The vascular disrupting agent (VDA) BNC105P shows synergy with everolimus in preclinical models. The DisrupTOR-1 trial included a phase I component exploring this combination and a randomized phase II component comparing everolimus with BNC105P (Arm A) to everolimus monotherapy (Arm B) (Pal et al. ESMO 2014). Methods: Pts with clear cell mRCC and 1-2 prior therapies (including ≥1 VEGF-TKI) were randomized in the phase II study component. In Arm A, patients received a 7 day lead-in dose of everolimus followed by dosing with BNC105P. Patients in Arm A had optional blood collections prior to administration of BNC105P and 3 hours after receiving BNC105P. A fluorescence-based assay was used to characterize a broad panel of analytes at each time point. Biomarkers were assessed in both a static and dynamic fashion. For the former, biomarkers were stratified by median value, and progression-free survival (PFS) was compared in resulting subgroups using the Kaplan-Meier method. For the latter, change in biomarker level before and after BNC105P infusion was stratified by median difference, and PFS was compared in resulting subgroups using the Kaplan-Meier method. Results: 139 pts were randomized with 69 and 67 evaluable pts in Arms A and B, respectively. Dynamic biomarkers were assessed in a total of 44 patients who received everolimus with BNC105P. Increases in matrix metalloproteinase-9 (MMP-9) and stem cell factor (SCF) were associated with improved PFS (p=0.0421 and p=0.0291, respectively). Decreases in sex hormone binding globulin (SHBG) and serum amyloid protein (SAP) were associated with improved PFS (p=0.0184 and p=0.0063). With respect to static biomarkers, elevated baseline ferritin and lower baseline IL-8 were associated with improved PFS (p=0.0291 and p=0.0149, respectively). Conclusions: Several static and dynamic biomarkers in the DisrupTOR-1 trial were associated with PFS. A prospective biomarker-driven study examining everolimus with BNC105P selected by baseline IL-8 and ferritin is in development. Clinical trial information: NCT01034631.