Development and evaluation of monoclonal antibodies against phosphatidylethanolamine binding protein 1 in pancreatic cancer patients

Insights of RKIP-Derived Suppression of Prostate Cancer

Simple Summary

Despite an intensive research effort in the past few decades, prostate cancer (PC) remains a top cause of cancer death in men, particularly in the developed world. The major cause of fatality is the progression of local prostate cancer to metastasis disease. Treatment of patients with metastatic prostate cancer (mPC) is generally ineffective. Based on the discovery of mPC relying on androgen for growth, many patients with mPC show an initial response to the standard of care: androgen deprivation therapy (ADT). However, lethal castration resistant prostate cancers (CRPCs) commonly develop. It is widely accepted that intervention of metastatic progression of PC is a critical point of intervention to reduce PC death. Accumulative evidence reveals a role of RKIP in suppression of PC progression towards mPC. We will review current evidence and discuss the potential utilization of RKIP in preventing mPC progression.

Abstract

Prostate cancer (PC) is a major cause of cancer death in men. The disease has a great disparity in prognosis. Although low grade PCs with Gleason scores ≤ 6 are indolent, high-risk PCs are likely to relapse and metastasize. The standard of care for metastatic PC (mPC) remains androgen deprivation therapy (ADT). Resistance commonly occurs in the form of castration resistant PC (CRPC). Despite decades of research efforts, CRPC remains lethal. Understanding of mechanisms underpinning metastatic progression represents the overarching challenge in PC research. This progression is regulated by complex mechanisms, including those regulating PC cell proliferation, epithelial–mesenchymal transition (EMT), and androgen receptor (AR) signaling. Among this PC metastatic network lies an intriguing suppressor of PC metastasis: the Raf kinase inhibitory protein (RKIP). Clinically, the RKIP protein is downregulated in PC, and showed further reduction in mPC. In xenograft mouse models for PC, RKIP inhibits metastasis. In vitro, RKIP reduces PC cell invasion and sensitizes PC cells to therapeutic treatments. Mechanistically, RKIP suppresses Raf-MEK-ERK activation and EMT, and modulates extracellular matrix. In return, Snail, NFκB, and the polycomb protein EZH2 contribute to inhibition of RKIP expression. In this review, we will thoroughly analyze RKIP’s tumor suppression actions in PC.

Metastasis Suppressor Genes in Pancreatic Cancer: An Update

ABSTRACT

Pancreatic cancer, especially pancreatic ductal adenocarcinoma (PDAC), has for long remained a deadly form of cancer characterized by high mortality rates resulting from metastasis to multiple organs. Several factors, including the late manifestation of the disease, partly amplified by lack of efficient screening methods, have hampered the drive to design an effective therapeutic strategy to treat this deadly cancer. Understanding the biology of PDAC progression and identifying critical genes regulating these processes are essential to overcome the barriers toward effective treatment. Metastasis suppressor genes have been shown to inhibit multiple steps in the metastatic cascade without affecting primary tumor formation and are considered to hold promise for treating metastatic cancers. In this review, we catalog the bona fide metastasis suppressor genes reported in PDAC and discuss their known mechanism of action.

Urinary diagnostic proteomic markers for dynapenia in cancer patients

Dynapenia is defined as the age-related loss of muscle strength, and plays a significant role in the loss of physical function and increased risk of disability among older individuals. The need for an early diagnosis supports the search for a biomarker that reflects muscle 'weakening'. This has previously proven difficult due to patient heterogeneity at presentation and lack of understanding of the underlying molecular mechanisms. The aim of the present study was to identify potential urinary biomarkers of dynapenia in patients undergoing potentially curative surgery for upper gastrointestinal cancer. Maximum isometric knee extensor strength (strain gauge) and maximum leg extensor power (Nottingham power rig) measurements were taken. Cut-off values for dynapenia were based on the Allied Dunbar national fitness survey. Values below the 5th percentile for the population matched for age and sex on the Allied Dunbar national fitness survey were used to stratify the cohort into dynapenic or normal. Urine samples taken at induction of anaesthesia were analysed by SELDI-TOF mass spectrometry using CM10 and IMAC30 chip-types to establish statistically significant m/z peak fingerprint patterns, followed by in-gel LC-MS/MS to identify molecular constituents. Statistical analysis of decision-tree calculations using Biomarker Pattern software resulted in models with sensitivities of 86 and 96%, specificities of 81 and 89%, and overall correctness of 84 and 93%, when applied to the entire cohort for power and strength measurement-based stratifications using the IMAC30 chip-type and the CM10 chip-type, respectively. The molecular identities of 10 peaks of interest were further investigated. After subtraction of potentially unrelated proteins, they were identified as fragments of Annexin A1, collagen α-1 (XV), perlecan and myotrophin. These results demonstrate that urinary screening can be used to define cancer-associated muscle weakness, and the identification of potential biomarkers could be invaluable in establishing a rapid test to measure and assess dynapenia in the clinical setting.

Quantitative proteomic profiling of tumor cell response to telomere dysfunction using isotope-coded protein labeling (ICPL) reveals interaction network of candidate senescence markers

Telomerase inhibition causes progressive telomere shortening and cellular senescence, which constitutes a universal barrier to tumor growth and therefore an attractive target for tumor therapy. To expand our previous studies, we investigated the global effects of telomere dysfunction on the proteome of tumor cells in order to find novel senescence biomarkers. Telomerase-deficient HCT-116 cell clones were analyzed by a quantitative proteomic approach using isotope-coded protein labeling (ICPL) and nanoflow-HPLC-MS/MS. Stringent reduction of the extensive proteomic data from this tumor cell model revealed a list of 59 markers including proteins identified in our former studies and a number of novel proteins involved in tumorigenesis and metastasis such as SFN, S100A4, ANXA2, and LGALS1. A loss of the chromatin protein HMGB2 was demonstrated not only in various telomerase-inhibited clones of different tumor cell lines, but also in normal human fibroblasts undergoing replicative senescence and in aging telomerase knockout mice. Impressively, a coherent and dense network of protein-protein interactions for the bulk of the markers and their implementation in signaling pathways involving key regulators for tumorigenesis were revealed. These results have an impact on the understanding of telomere- and senescence-related signal transduction in tumor cells in consideration of the general lack of senescence markers.

BIOLOGICAL SIGNIFICANCE

Induction of cellular senescence constitutes a potent concept for tumor therapy which interferes with immortalization and additional hallmarks of cancer. The application of a powerful quantitative proteomic approach using isotope-coded protein labeling to an approved model for senescence represented by telomerase inhibited tumor cells led to the identification of novel candidate biomarkers for telomere dysfunction and replicative senescence. Thereby, the identified markers not only fit in the context of the investigated processes with a relevance for additional hallmarks of cancer but are also involved in a strong interaction network and integrated in canonical pathways centered around key cancer-relevant proteins. These potential markers alone or in combination will significantly extend the view on telomere-associated signal transduction in tumor cells and contribute to the field of cellular senescence and aging in consideration of the general lack of biomarkers in this regard.

Development and optimization of an antibody array method for potential cancer biomarker detection

Biomarkers play an important role in the detection at an early stage of pancreatic cancer. The aim of the present study was to optimize the conditions of antibody arrays for detecting Hippocalcin-like 1 (HPCAL1), phosphatidylethanolamine binding protein 1 (PEBP1), lectin galactoside-binding soluble 7 (LGALS7), and serpin peptidase inhibitor clade E member 2 (SERPINE2) as biomarkers for pancreatic cancer detection in a single assay and to investigate antibodies' specificity and cross-reactivity. Capture antibodies against HPCAL1, PEBP1, LGALS7 and SERPINE2 were printed on nitrocellulose coated glass slides. HPCAL1, PEBP1, LGALS7 and SERPINE2 proteins with different concentrations were incubated with the capture antibodies at different temperatures for different time periods. Biotinylated detection antibodies recognizing a different epitope on the captured proteins and a secondary detection molecule (Streptavidin-PE) were used to detect fluorescent signals. The arrays showed the strongest signals when the concentration of the capture antibodies was at 500 µg/mL in PBST0.05 (PBS with 0.05% Tween-20), and the slides were incubated overnight at 4°C. The lowest protein concentration for detection was 2 ng/mL. Each antibody demonstrated high specificity to the corresponding antigen in detecting a mixture of 4 proteins without significant cross-reactivity. The fluorescence and biomarker concentration displayed a linear correlation. The antibody microarray system could be a useful tool for potential biomarker detection for pancreatic cancer.

Lipophilicity of flavonoid complexes with iron(II) and their interaction with liposomes

We studied complex formation of flavonoids quercetin and taxifolin with iron(II) and the complex influence on phase transitions of phospholipid bilayer. UV-Vis spectroscopy revealed that the stoichiometry of flavonoid/iron complexes was equal to 3:2 and 2:1. Molecular modeling and experimental measurements demonstrated the increase of flavonoids lipophilicity after the complex formation. A considerable influence of quercetin-iron complex on Palmitoyl-Oleoyl-Phosphatidylethanolamine transitions from bilayer to hexagonal HII phase was detected by differential scanning calorimetry. The obtained data are related to flavonoid/iron complexes bioavailability, their influence on cell membrane functioning, and should be considered in designing liposomal vehicles for drug and gene delivery.

Raf kinase inhibitory protein is required for cerebellar long-term synaptic depression by mediating PKC-dependent MAPK activation

It was demonstrated previously that a positive feedback loop, including protein kinase C (PKC) and mitogen-activated protein kinase (MAPK), is required for the gradual expression of cerebellar long-term depression (LTD). PKC and MAPK are mutually activated in this loop. MAPK-dependent PKC activation is likely to be mediated by phospholipase A2. On the other hand, it is not clear how PKC activates MAPK. Therefore, the entire picture of this loop was not fully understood. We here test the hypothesis that this loop is completed by the PKC substrate, Raf kinase inhibitory protein (RKIP). To test this hypothesis, we used a mutant form of RKIP that is not phosphorylated by PKC and thus constitutively inhibits Raf-1 and MEK, upstream kinases of MAPK. When this RKIP mutant was introduced into Purkinje cells of mouse cerebellar slices through patch-clamp electrodes, LTD was blocked, while wild-type (WT) RKIP had no effect on LTD. Physiological epistasis experiments demonstrated that RKIP works downstream of PKC and upstream of MAPK during LTD induction. Furthermore, biochemical analyses demonstrated that endogenous RKIP dissociates from Raf-1 and MEK during LTD induction in a PKC-dependent manner, suggesting that RKIP binding-dependent inhibition of Raf-1 and MEK is removed upon LTD induction. We therefore conclude that PKC-dependent regulation of RKIP leads to MAPK activation, with RKIP completing the positive feedback loop that is required for LTD.