Pancreatic cancer: current standards, working towards a new therapeutic approach

Phosphatidylserine: The Unique Dual-Role Biomarker for Cancer Imaging and Therapy

Cancer is among the leading causes of death worldwide. In recent years, many cancer-associated biomarkers have been identified that are used for cancer diagnosis, prognosis, screening, and early detection, as well as for predicting and monitoring carcinogenesis and therapeutic effectiveness. Phosphatidylserine (PS) is a negatively charged phospholipid which is predominantly located in the inner leaflet of the cell membrane. In many cancer cells, PS externalizes to the outer cell membrane, a process regulated by calcium-dependent flippases and scramblases. Saposin C coupled with dioleoylphosphatidylserine (SapC-DOPS) nanovesicle (BXQ-350) and bavituximab, (Tarvacin, human-mouse chimeric monoclonal antibodies) are cell surface PS-targeting drugs being tested in clinical trial for treating a variety of cancers. Additionally, a number of other PS-selective agents have been used to trigger cytotoxicity in tumor-associated endothelial cells or cancer cells in pre-clinical studies. Recent studies have demonstrated that upregulation of surface PS exposure by chemodrugs, radiation, and external electric fields can be used as a novel approach to sensitize cancer cells to PS-targeting anticancer drugs. The objectives of this review are to provide an overview of a unique dual-role of PS as a biomarker/target for cancer imaging and therapy, and to discuss PS-based anticancer strategies that are currently under active development.

Hexokinase 2 dimerization and interaction with voltage-dependent anion channel promoted resistance to cell apoptosis induced by gemcitabine in pancreatic cancer

Gemcitabine (GEM) is the standard chemotherapy drug for pancreatic cancer. Because of widespread drug resistance, the effect is limited. Therefore, it is urgent to reveal the underlying mechanism. Glycolysis is the most remarkable character of tumor aberrant metabolism, which plays vital roles on tumor drug resistance. Hexokinase 2 (HK2), as the key enzyme regulating the first‐step reaction of glycolysis, is overexpressed in many kinds of tumors. The putative role of HK2 resisting GEM therapy was investigated in this study. We found that HK2 was overexpressed in pancreatic cancer and associated with poor prognosis. HK2 knockdown decreased pancreatic cancer cell proliferation, migration viability, and promoted cell apoptosis in vitro. HK2 high expression in pancreatic cancer showed GEM resistance. HK2 knockdown increased the sensitivity of pancreatic cancer cell to GEM, the growth of xenograft tumor with HK2 knockdown was also further decreased with the GEM treatment compared with control in vivo. GEM‐resistant pancreatic cancer showed the increase of HK2 dimer rather than HK2 mRNA or protein. Our study revealed that the ROS derived from GEM promoted HK2 dimerization combining with voltage‐dependent anion channel, which resulted in the resistance to GEM. Meanwhile, our study established a new sight for GEM resistance in pancreatic cancer.

"Eat me" imaging and therapy

Clearance of apoptotic debris is a vital role of the innate immune system. Drawing upon principles of apoptotic clearance, convenient delivery vehicles including intrinsic anti-inflammatory characteristics and specificity to immune cells can be engineered to aid in drug delivery. In this article, we examine the use of phosphatidylserine (PtdSer), the well-known "eat-me" signal, in nanoparticle-based therapeutics making them highly desirable "meals" for phagocytic immune cells. Use of PtdSer facilitates engulfment of nanoparticles allowing for imaging and therapy in various pathologies and may result in immunomodulation. Furthermore, we discuss the targeting of the macrophages and other cells at sites of inflammation in disease. A thorough understanding of the immunobiology of "eat-me" signals is requisite for the successful application of "eat-me"-bearing materials in biomedical applications.

Pancreatic cancer: BRCA mutation and personalized treatment

The highly heterozygous nature of pancreatic cancer is partially responsible for its therapeutic ineffectiveness and resistance. Therefore, the ability to identify subgroups of pancreatic cancer with unique biological characteristics and treatment response is urgently needed. In addition to breast and ovarian cancer, pancreatic cancer is the third most common cancer type that is related to the early onset (BRCA) gene mutation in breast cancer. Mounting evidence has demonstrated that BRCA1/2-mutant breast and ovarian cancers are highly sensitive to DNA damage-related treatment, including poly(ADP-ribose) polymerase inhibitors (PARPi) and platinum-based agents. Preliminary evidence also showed promising results for DNA damage-related treatment in BRCA1/2-mutant pancreatic cancer. Importantly, several prospective clinical trials of PARPi-based regimens are underway for BRCA1/2-mutated pancreatic cancer. Pancreatic cancer with a BRCA1/2 mutation is a small subgroup with a promising therapeutic strategy.

Imaging and Therapy of Pancreatic Cancer with Phosphatidylserine-Targeted Nanovesicles

Pancreatic cancer remains one of the most intractable cancers, with a dismal prognosis reflected by a 5-year survival of ~6%. Since early disease symptoms are undefined and specific biomarkers are lacking, about 80% of patients present with advanced, inoperable tumors that represent a daunting challenge. Despite many clinical trials, no single chemotherapy agent has been reliably associated with objective response rates above 10% or median survival longer than 5 to 7 months. Although combination chemotherapy regimens have in recent years provided some improvement, overall survival (8-11 months) remains very poor. There is therefore a critical need for novel therapies that can improve outcomes for pancreatic cancer patients. Here, we present a summary of the current therapies used in the management of advanced pancreatic cancer and review novel therapeutic strategies that target tumor biomarkers. We also describe our recent research using phosphatidylserine-targeted saposin C-coupled dioleoylphosphatidylserine nanovesicles for imaging and therapy of pancreatic cancer.

Characteristics of gastrointestinal hemorrhage associated with pancreatic cancer: A retrospective review of 246 cases

While gastrointestinal (GI) hemorrhage is common in the general population, few studies have evaluated large numbers of GI hemorrhage patients with pancreatic cancer. The clinical features and potential risk factors of GI hemorrhage with pancreatic cancer was investigated in the present study and the effect of GI hemorrhage on survival rate was examined. Patients enrolled in the present study had pathologically proven pancreatic cancer, and received treatment between August 2006 and 2012. Their medical records were retrospectively reviewed. The data for the present study were obtained from a review of 246 patients with pancreatic cancer (average age, 63.4±10.92 years; 190 male cases, 56 female cases). In addition, 73 cases had stage I-II, 173 had stage III-IV, and only 67 cases (27.2%) were candidates for curative pancreatectomy. Among them, 32 cases (13.0%) were clinically diagnosed with GI hemorrhage. A total of 24 cases were male patients and the other 8 cases were female, the cases of hemorrhage history and alcoholism were 2 and 29 cases, respectively. The major initial clinical symptoms of GI hemorrhage included 18 patients with melena or blood stool (56.25%), 9 with haematemesis (28.13%), 3 with abdominal distention (9.37%) and 2 with stomach ache (6.25%). The independent risk factor for GI hemorrhage was tumor initial stage of IV. A continuous increase in carbohydrate antigen 19-9 (CA19-9) may be a warning of GI hemorrhage, particularly when it is >1,000 U/ml. The most frequent method of hemostasis was combination therapy (n=12, 37.5%). Only 3 cases (9.3%) of these 32 GI hemorrhage patients were blood stanched and only 10 patients (31.2%) received gastroscopy. The time from GI hemorrhage to fatality is extremely short (median 30 days, range from 1 h to 65 days), and the median overall survival time of the patients with GI hemorrhage was 9.0 months (range, 2.0-16.0 months) and was significantly shorter than that of patients without GI hemorrhage [14.5 months (range, 0.5-48.0 months)]. In conclusion, although GI hemorrhage was not common in patients with pancreatic cancer, it is critical. GI hemorrhage was controlled with endoscopic hemostasis. Clinicians should fully assess the risk factors of GI hemorrhage (such as alcohol, smoking, past hemorrhage history, initial stage, tumor location and CA19-9 level at diagnosis of pancreatic cancer) when the pancreatic cancer patients were on admission, particularly for patients of the late stage, preventive measures should be investigated to reduce suffering.

SapC-DOPS nanovesicles induce Smac- and Bax-dependent apoptosis through mitochondrial activation in neuroblastomas

BACKGROUND

High toxicity, morbidity and secondary malignancy render chemotherapy of neuroblastoma inefficient, prompting the search for novel compounds. Nanovesicles offer great promise in imaging and treatment of cancer. SapC-DOPS, a stable nanovesicle formed from the lysosomal protein saposin C and dioleoylphosphatidylserine possess strong affinity for abundantly exposed surface phosphatidylserine on cancer cells. Here, we show that SapC-DOPS effectively targets and suppresses neuroblastoma growth and elucidate the molecular mechanism of SapC-DOPS action in neuroblastoma in vitro.

METHODS

In vivo targeting of neuroblastoma was assessed in xenograft mice injected intravenously with fluorescently-labeled SapC-DOPS. Xenografted tumors were also used to demonstrate its therapeutic efficacy. Apoptosis induction in vivo was evaluated in tumor sections using the TUNEL assay. The mechanisms underlying the induction of apoptosis by SapC-DOPS were addressed through measurements of cell viability, mitochondrial membrane potential (ΔΨM), flow cytometric DNA fragmentation assays and by immunoblot analysis of second mitochondria-derived activator of caspases (Smac), Bax, Cytochrome c (Cyto c) and Caspase-3 in the cytosol or in mitochondrial fractions of cultured neuroblastoma cells.

RESULTS

SapC-DOPS showed specific targeting and prevented the growth of human neuroblastoma xenografts in mice. In neuroblastoma cells in vitro, apoptosis occurred via a series of steps that included: (1) loss of ΔΨM and increased mitochondrial superoxide formation; (2) cytosolic release of Smac, Cyto c, AIF; and (3) mitochondrial translocation and polymerization of Bax. ShRNA-mediated Smac knockdown and V5 peptide-mediated Bax inhibition decreased cytosolic Smac and Cyto c release along with caspase activation and abrogated apoptosis, indicating that Smac and Bax are critical mediators of SapC-DOPS action. Similarly, pretreatment with the mitochondria-stabilizing agent bongkrekic acid decreased apoptosis indicating that loss of ΔΨM is critical for SapC-DOPS activity. Apoptosis induction was not critically dependent on reactive oxygen species (ROS) production and Cyclophilin D, since pretreatment with N-acetyl cysteine and cyclosporine A, respectively, did not prevent Smac or Cyto c release.

CONCLUSIONS

Taken together, our results indicate that SapC-DOPS acts through a mitochondria-mediated pathway accompanied by an early release of Smac and Bax. Specific tumor-targeting capacity and anticancer efficacy of SapC-DOPS supports its potential as a dual imaging and therapeutic agent in neuroblastoma therapy.