Ectodomain shedding of extracellular and membrane proteins is of fundamental importance for cell–cell communication in neoplasias. A Disintegrin And Metalloproteinase (ADAM) proteases constitute a family of multifunctional, membrane-bound proteins with traditional sheddase functions. Their protumorigenic potential has been attributed to both, essential (ADAM10 and ADAM17) and ‘dispensable’ ADAM proteases (ADAM8, 9, 12, 15, and 19). Of specific interest in this review is the ADAM proteinase ADAM8 that has been identified as a significant player in aggressive malignancies including breast, pancreatic, and brain cancer. High expression levels of ADAM8 are associated with invasiveness and predict a poor patient outcome, indicating a prognostic and diagnostic potential of ADAM8. Current knowledge of substrates and interaction partners gave rise to the hypothesis that ADAM8 dysregulation affects diverse processes in tumor biology, attributable to different functional cores of the multidomain enzyme. Proteolytic degradation of extracellular matrix (ECM) components, cleavage of cell surface proteins, and subsequent release of soluble ectodomains promote cancer progression via induction of angiogenesis and metastasis. Moreover, there is increasing evidence for significance of a non-proteolytic function of ADAM8. With the disintegrin (DIS) domain ADAM8 binds integrins such as β1 integrin, thereby activating integrin signaling pathways. The cytoplasmic domain is critical for that activation and involves focal adhesion kinase (FAK), extracellular regulated kinase (ERK1/2), and protein kinase B (AKT/PKB) signaling, further contributing to cancer progression and mediating chemoresistance against first-line therapies. This review highlights the remarkable effects of ADAM8 in tumor biology, concluding that pharmacological inhibition of ADAM8 represents a promising therapeutic approach not only for monotherapy, but also for combinatorial therapies.
DNA-damaging drugs induce a plethora of molecular and cellular alterations in tumor cells, but their interrelationship is largely obscure. Here, we show that carboplatin treatment of human ovarian carcinoma SKOV3 cells triggers an ordered sequence of events, which precedes the emergence of mitotic chemoresistant cells. The initial phase of cell death after initiation of carboplatin treatment is followed around day 14 by the emergence of a mixed cell population consisting of cycling, cell cycle-arrested and senescent cells. At this stage, giant cells make up >80% of the cell population, p21 (CDKN1A) in strongly induced, and cell numbers remain nearly static. Subsequently, cell death decreases, p21 expression drops to a low level and cell divisions increase, including regular mitoses of giant cells and depolyploidization by multi-daughter divisions. These events are accompanied by the upregulation of stemness markers and a pro-inflammatory secretory phenotype, peaking after approximately 14 days of treatment. At the same time the cells initiate epithelial to mesenchymal transition, which over the subsequent weeks continuously increases, concomitantly with the emergence of highly proliferative, migratory, dedifferentiated, pro-inflammatory and chemoresistant cells (SKOV3-R). These cells are anchorageindependent and grow in a 3D collagen matrix, while cells on day 14 do not survive under these conditions, indicating that SKOV3-R cells were generated thereafter by the multi-stage process described above. This process was essentially recapitulated with the ovarian carcinoma cell line IGROV-1. Our observations suggest that transitory cells characterized by polyploidy, features of stemness and a pro-inflammatory secretory phenotype contribute to the acquisition of chemoresistance.
BackgroundNeoplastic invasion into leptomeninges and subarachnoid space, resulting in neoplastic meningitis (NM) is a fatal complication of advanced solid and hematological neoplasms. Identification of malignant involvement of the cerebrospinal fluid (CSF) early in the disease course has crucial prognostic and therapeutic implications, but remains challenging. As indicators of extracellular matrix (ECM) degradation and breakdown of the blood–brain-barrier, Matrix Metalloproteases (MMPs) and A Disintegrin and Metalloproteases (ADAMs) are potential analytes for cerebral pathophysiology and metastatic dissemination of tumor cells into the CSF.MethodsWe compared protease activities in CSF samples from patients with NM and control individuals using FRET-based metalloprotease substrates with distinct enzyme selectivity profiles in a real-time, multiplex approach termed “proteolytic activity matrix assay” (PrAMA). Protease activity dynamics can be tracked by fluorescence changes over time. By simultaneously monitoring a panel of 5 FRET-substrate cleavages, a proteolytic signature can be identified and analyzed to infer the activities of multiple specific proteases. Distinct patterns of substrate cleavage comparing disease vs. control samples allow rapid, reproducible and sensitive discrimination even in small volumes of CSF.ResultsIndividual substrate cleavage rates were linked to distinct proteases, and PrAMA computational inference implied increased activities of MMP-9, ADAM8 and ADAM17 (4–5-fold on average) in CSF samples from NM patients that were inhibitable by the metalloprotease inhibitor batimastat (BB-94). The activities of these proteases correlated with blood–brain barrier impairment. Notably, CSF cell counts were not found to directly reflect the protease activities observed in CSF samples from NM patients; this may explain the frequent clinical observation of negative cytology in NM patients.ConclusionPrAMA analysis of CSF samples is a potential diagnostic method for sensitive detection of NM and may be suitable for the clinical routine.Electronic supplementary materialThe online version of this article (doi:10.1186/s12987-017-0070-5) contains supplementary material, which is available to authorized users.
ADAM8 as a membrane-anchored metalloproteinase-disintegrin is upregulated under pathological conditions such as inflammation and cancer. As active sheddase, ADAM8 can cleave several membrane proteins, among them the low-affinity receptor FcεRII CD23. Hydroxamate-based inhibitors are routinely used to define relevant proteinases involved in ectodomain shedding of membrane proteins. However, for ADAM proteinases, common hydroxamates have variable profiles in their inhibition properties, commonly known for ADAM proteinases 9, 10 and 17. Here, we determined the inhibitor profile of human ADAM8 for eight ADAM/MMP inhibitors byin vitroassays using recombinant ADAM8 as well as thein vivoinhibition in cell-based assays using HEK293 cells to monitor the release of soluble CD23 by ADAM8. ADAM8 activity is inhibited by BB94 (Batimastat), GW280264, FC387 and FC143 (two ADAM17 inhibitors), made weaker by GM6001, TAPI2 and BB2516 (Marimastat), while no inhibition was observed for GI254023, an ADAM10 specific inhibitor. Modeling of inhibitor FC143 bound to the catalytic sites of ADAM8 and ADAM17 reveals similar geometries in the pharmacophoric regions of both proteinases, which is different in ADAM10 due to replacement in the S1 position of T300 (ADAM8) and T347 (ADAM17) by V327 (ADAM10). We conclude that ADAM8 inhibitors require maximum selectivity over ADAM17 to achieve specific ADAM8 inhibition.
BACKGROUND: Brain metastases treatments are usually based on surgery and radiation therapies with poor patient survival. Cellular adhesion molecules (CAMs) are promiscuous proteins highly involved in tumour progression. Owing to their dual functionality in structure and signalling, CAMs have emerged as potential targets in the clinic. It has been shown that CAMs can modulate radiation response in different types of tumours, triggering either apoptosis or resistance. However, this complex behaviour has not been studied in brain metastasis. In recent years, we have demonstrated a role of several CAMs during brain metastasis progression. For example, disrupting interactions between circulating tumour cells and brain vasculature using antibodies against ALCAM (CD166) and VLA-4 (α4β1), resulted in a significant decrease in metastatic colonies. Similarly, after LFA-1 (αLβ2) knockdown in tumour cells, brain metastasis growth was greatly reduced. On this basis, the aim of the current study was to determine the effect of concomitant stereotactic brain radiotherapy (SARRP) and anti-CAM treatments in breast cancer brain metastasis in vivo models. METHODS: MDA231Br human breast carcinoma cells were treated with shRNA against either LFA1 or ALCAM. Cells were intracerebrally injected (5.000 cells/0.5 µl PBS) into the left striatum of female SCID mice. At day 14 after tumour injection, animals received a single dose of 15Gy in the striatum. Animals were culled 21 days after injection and brains processed for tumour quantitation. RESULTS AND DISCUSSION: As previously shown, animals injected with LFA1 K.D. cells showed a 70% reduction in tumour burden 21 days after tumour implantation compared to those injected with the parent MDA231Br cells. Moreover, when irradiation was added, a synergistic effect (85% decrease in tumour growth) was evident in LFA1 K.D. injected animals. This study is particularly interesting from a clinical perspective, since anti-LFA1 therapies are common in the clinic for transplant rejection, joint inflammation or psoriasis treatments. In contrast, although animals injected with ALCAM K.D. MDA231Br cells showed a similar reduction (~80%) in tumour burden 21 days after injection, following irradiation tumour burden was comparable to that seen with the parental MDA231Br cells. These data suggest a pivotal role for ALCAM in brain metastasis progression and radiation response. Unravelling LFA-1 and ALCAM pathways in brain metastasis progression may lead to the successful combination of current clinical anti-inflammatory and radiation therapies and increase patient life expectancy.
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