SEL1L expression in prostatic intraepithelial neoplasia and adenocarcinoma: an immunohistochemical study

SEL1L plays a major role in human malignant gliomas

Suppressor of Lin-12-like (C. elegans) (SEL1L) participates in the endoplasmic reticulum-associated protein degradation pathway, malignant transformation and stem cell biology. We explored the role of SEL1L in 110 adult gliomas, of different molecular subtype and grade, in relation to cell proliferation, stemness, glioma-associated microglia/macrophages (GAMs), prognostic markers and clinical outcome. SEL1L protein expression was assessed by immunohistochemistry and Western blotting. Genetic and epigenetic alterations were detected by molecular genetics techniques. SEL1L was overexpressed in anaplastic gliomas (World Health Organization [WHO] grade III) and in glioblastoma (GB, WHO grade IV) with the highest labelling index (LI) in the latter. Immunoreactivity was significantly associated with histological grade (p = 0.002) and cell proliferation index Ki-67/MIB-1 (p = 0.0001). In GB, SEL1L co-localised with stemness markers Nestin and Sox2. Endothelial cells and vascular pericytes of proliferative tumour blood vessels expressed SEL1L suggesting a role in tumour neo-vasculature. GAMs consistently expressed SEL1L. SEL1L overexpression was significantly associated with TERT promoter mutations (p = 0.0001), EGFR gene amplification (p = 0.0013), LOH on 10q (p = 0.0012) but was mutually exclusive with IDH1/2 mutations (p = 0.0001). SEL1L immunoreactivity correlated with tumour progression and cell proliferation, conditioning poor patient survival and response to therapy. This study emphasises SEL1L as a potential biomarker for the most common subgroup of TERT mutant/EGFR amplified/IDH-WT GBs.

Identification of genetic variants predictive of early onset pancreatic cancer through a population science analysis of functional genomic datasets

Biomarkers are critically needed for the early detection of pancreatic cancer (PC) are urgently needed. Our purpose was to identify a panel of genetic variants that, combined, can predict increased risk for early-onset PC and thereby identify individuals who should begin screening at an early age. Previously, we identified genes using a functional genomic approach that were aberrantly expressed in early pathways to PC tumorigenesis. We now report the discovery of single nucleotide polymorphisms (SNPs) in these genes associated with early age at diagnosis of PC using a two-phase study design. In silico and bioinformatics tools were used to examine functional relevance of the identified SNPs. Eight SNPs were consistently associated with age at diagnosis in the discovery phase, validation phase and pooled analysis. Further analysis of the joint effects of these 8 SNPs showed that, compared to participants carrying none of these unfavorable genotypes (median age at PC diagnosis 70 years), those carrying 1–2, 3–4, or 5 or more unfavorable genotypes had median ages at diagnosis of 64, 63, and 62 years, respectively (P = 3.0E–04). A gene-dosage effect was observed, with age at diagnosis inversely related to number of unfavorable genotypes (P_trend = 1.0E–04). Using bioinformatics tools, we found that all of the 8 SNPs were predicted to play functional roles in the disruption of transcription factor and/or enhancer binding sites and most of them were expression quantitative trait loci (eQTL) of the target genes. The panel of genetic markers identified may serve as susceptibility markers for earlier PC diagnosis.

mSEL-1L deficiency affects vasculogenesis and neural stem cell lineage commitment

mSEL-1L is a highly conserved ER-resident type I protein, involved in the degradation of misfolded peptides through the ubiquitin-proteasome system (UPS), a pathway known to control the plasticity of the vascular smooth muscle cells (VSMC) phenotype and survival. In this article, we demonstrate that mSEL-1L deficiency interferes with the murine embryonic vascular network, showing particular irregularities in the intracranic and intersomitic neurovascular units and in the cerebral capillary microcirculation. During murine embryogenesis, mSEL-1L is expressed in cerebral areas known to harbor progenitor neural cells, while in the adult brain the protein is specifically restricted to the stem cell niches, co-localizing with Sox2 and Nestin. Null mice are characterized by important defects in the development of telenchephalic regions, revealing conspicuous aberration in neural stem cell lineage commitment. Moreover, mSEL-1L depletion in vitro and in vivo appears to affect the harmonic differentiation of the NSCs, by negatively influencing the corticogenesis processes. Overall, the data presented suggests that the drastic phenotypic characteristics exhibited in mSEL-1L null mice can, in part, be explained by the negative influence it plays on Notch1 signaling pathway.

SEL1L SNP rs12435998, a predictor of glioblastoma survival and response to radio-chemotherapy

The suppressor of Lin-12-like (C. elegans) (SEL1L) is involved in the endoplasmic reticulum (ER)-associated degradation pathway, malignant transformation and stem cells.

In 412 formalin-fixed and paraffin-embedded brain tumors and 39 Glioblastoma multiforme (GBM) cell lines, we determined the frequency of five SEL1L single nucleotide genetic variants with regulatory and coding functions by a SNaPShot™ assay. We tested their possible association with brain tumor risk, prognosis and therapy.

We studied the in vitro cytotoxicity of valproic acid (VPA), temozolomide (TMZ), doxorubicin (DOX) and paclitaxel (PTX), alone or in combination, on 11 GBM cell lines, with respect to the SNP rs12435998 genotype.

The SNP rs12435998 was prevalent in anaplastic and malignant gliomas, and in meningiomas of all histologic grades, but unrelated to brain tumor risks. In GBM patients, the SNP rs12435998 was associated with prolonged overall survival (OS) and better response to TMZ-based radio-chemotherapy. GBM stem cells with this SNP showed lower levels of SEL1L expression and enhanced sensitivity to VPA.

Down-modulation of SEL1L, an unfolded protein response and endoplasmic reticulum-associated degradation protein, sensitizes glioma stem cells to the cytotoxic effect of valproic acid

Valproic acid (VPA), an histone deacetylase inhibitor, is emerging as a promising therapeutic agent for the treatments of gliomas by virtue of its ability to reactivate the expression of epigenetically silenced genes. VPA induces the unfolded protein response (UPR), an adaptive pathway displaying a dichotomic yin yang characteristic; it initially contributes in safeguarding the malignant cell survival, whereas long-lasting activation favors a proapoptotic response. By triggering UPR, VPA might tip the balance between cellular adaptation and programmed cell death via the deregulation of protein homeostasis and induction of proteotoxicity. Here we aimed to investigate the impact of proteostasis on glioma stem cells (GSC) using VPA treatment combined with subversion of SEL1L, a crucial protein involved in homeostatic pathways, cancer aggressiveness, and stem cell state maintenance. We investigated the global expression of GSC lines untreated and treated with VPA, SEL1L interference, and GSC line response to VPA treatment by analyzing cell viability via MTT assay, neurosphere formation, and endoplasmic reticulum stress/UPR-responsive proteins. Moreover, SEL1L immunohistochemistry was performed on primary glial tumors. The results show that (i) VPA affects GSC lines viability and anchorage-dependent growth by inducing differentiative programs and cell cycle progression, (ii) SEL1L down-modulation synergy enhances VPA cytotoxic effects by influencing GSCs proliferation and self-renewal properties, and (iii) SEL1L expression is indicative of glioma proliferation rate, malignancy, and endoplasmic reticulum stress statuses. Targeting the proteostasis network in association to VPA treatment may provide an alternative approach to deplete GSC and improve glioma treatments.

Molecular chaperones as therapeutic targets to counteract proteostasis defects

The health of cells is preserved by the levels and correct folding states of the proteome, which is generated and maintained by the proteostasis network, an integrated biological system consisting of several cytoprotective and degradative pathways. Indeed, the health conditions of the proteostasis network is a fundamental prerequisite to life as the inability to cope with the mismanagement of protein folding arising from genetic, epigenetic, and micro-environment stress appears to trigger a whole spectrum of unrelated diseases. Here we describe the potential functional role of the proteostasis network in tumor biology and in conformational diseases debating on how the signaling branches of this biological system may be manipulated to develop more efficacious and selective therapeutic strategies. We discuss the dual strategy of these processes in modulating the folding activity of molecular chaperones in order to counteract the antithetic proteostasis deficiencies occurring in cancer and loss/gain of function diseases. Finally, we provide perspectives on how to improve the outcome of these disorders by taking advantage of proteostasis modeling.

SEL1L, an UPR response protein, a potential marker of colonic cell transformation

BACKGROUND

SEL1L gene product is implicated in the endoplasmic reticulum (ER)-associated protein degradation and Unfolded Protein Response pathways. This gene and associated miRNAs have been indicated as predictive and prognostic markers of pancreatic cancer.

AIM

Explore the role of SEL1L in colorectal cancer (CRC) progression.

METHODS

SEL1L expression was analysed immunohistochemically in 153 adenomas and 71 CRCs from African American and North Italian patients. The distribution of stained cells was determined by computing median and inter quartile range. The receiver operating characteristics plot was used as discriminate power of SEL1L expression, CRC diagnosis and the effects on patient survival.

RESULTS

SEL1L was low in normal mucosa and confined to few scattered cells at the base crypt of the villi and in the foveolar glandular compartment. The highest levels were in Paneth cells within the lysosomes. The enterocytic progenitor cells and mature enterocytes showed less cytoplasmic staining. In CRCs, SEL1L expression significantly correlated with the progression from adenoma to carcinoma (P = 0.0001) being stronger in well-to-moderately differentiated cancers. No correlation was found with other clinicopathological characteristics or ethnicity.

CONCLUSIONS

SEL1L expression is a potential CRC tissue biomarker since its expression is significantly higher in adenoma cells with respect to normal mucosa. The levels of expression decrease sensibly in undifferentiated CRC cancers. Interestingly, Paneth cells contain high levels of SEL1L protein that could indicate pre-neoplastic mucosa undergoing neoplastic transformation. Since SEL1L's major function lies within ER stress and active ERAD response, it may identify CRCs with differentiated secretory phenotype and acute cellular stress.

Secretion of novel SEL1L endogenous variants is promoted by ER stress/UPR via endosomes and shed vesicles in human cancer cells

We describe here two novel endogenous variants of the human endoplasmic reticulum (ER) cargo receptor SEL1LA, designated p38 and p28. Biochemical and RNA interference studies in tumorigenic and non-tumorigenic cells indicate that p38 and p28 are N-terminal, ER-anchorless and more stable relative to the canonical transmembrane SEL1LA. P38 is expressed and constitutively secreted, with increase after ER stress, in the KMS11 myeloma line and in the breast cancer lines MCF7 and SKBr3, but not in the non-tumorigenic breast epithelial MCF10A line. P28 is detected only in the poorly differentiated SKBr3 cell line, where it is secreted after ER stress. Consistently with the presence of p38 and p28 in culture media, morphological studies of SKBr3 and KMS11 cells detect N-terminal SEL1L immunolabeling in secretory/degradative compartments and extracellularly-released membrane vesicles. Our findings suggest that the two new SEL1L variants are engaged in endosomal trafficking and secretion via vesicles, which could contribute to relieve ER stress in tumorigenic cells. P38 and p28 could therefore be relevant as diagnostic markers and/or therapeutic targets in cancer.

Widespread deregulation of microRNA expression in human prostate cancer

MicroRNAs (miRNAs) are small regulatory RNAs that can regulate gene expression by binding to mRNA sequences and repressing target-gene expression post-transcriptionally, either by inhibiting translation or promoting RNA degradation. We have analysed expression of 328 known and 152 novel human miRNAs in 10 benign peripheral zone tissues and 16 prostate cancer tissues using microarrays and found widespread, but not universal, downregulation of miRNAs in clinically localized prostate cancer relative to benign peripheral zone tissue. These findings have been verified by real-time RT-PCR assays on select miRNAs, including miR-125b, miR-145 and let-7c. The downregulated miRNAs include several with proven target mRNAs whose proteins have been previously shown to be increased in prostate cancer by immunohistochemistry, including RAS, E2F3, BCL-2 and MCL-1. Using a bioinformatics approach, we have identified additional potential mRNA targets of one of the miRNAs, (miR-125b) that are upregulated in prostate cancer and confirmed increased expression of one of these targets, EIF4EBP1, in prostate cancer tissues. Our findings indicate that changes in miRNA expression may have an important role in the biology of human prostate cancer.

SEL1L affects human pancreatic cancer cell cycle and invasiveness through modulation of PTEN and genes related to cell-matrix interactions

Previously, it was reported that SEL1L is able to decrease the aggressive behavior of human pancreatic tumor cells both in vitro and in vivo. To gain insights into the involvement of SEL1L in tumor invasion, we performed gene expression analysis on the pancreatic cancer cell line Suit-2 subjected to two complementary strategies: upregulation and downregulation of SEL1L expression by stable transfection of the entire cDNA under an inducible promoter and by RNA-mediated interference. SuperArray and real-time analysis revealed that SEL1L modulates the expression of the matrix metalloproteinase inhibitors TIMP1 (P < .04-.03) and TIMP2 (P < .03-.05), and the PTEN gene (P < .03-.05). Gene expression modulations correlate with the decrease in invasive ability (P < .05) and in accumulation of SEL1L-expressing cells in G1. Taken together, our data indicate that SEL1L alters the expression of mediators involved in the remodeling of the extracellular matrix by creating a microenvironment that is unfavorable to invasive growth and by affecting cell cycle progression through promotion of G1 accumulation.