Biology subjects

Knappskog, S.

Publications and source records attributed to Knappskog, S..

7 recordsLinked to original sources

bioRxiv2024

Interactions between neutrophils and macrophages harboring gram-negative bacteria promote obesity-associated breast cancer

Obesity promotes a more aggressive breast cancer phenotype. Through spatial and single-cell-based analysis of hormone receptor-negative breast cancers, we identify a subset of tumor-associated neutrophils (TANs) positive for granzyme B (GZMB) enriched in the tumor microenvironment of obese patients. In breast tumors evolved in obese environments, TANs are in proximity of M2 polarized macrophages containing lipopolysaccharides (LPS) from gram-negative bacteria. Pyroptosis of macrophages releases bacterial LPS, activating local GZMB+ TANs. This induces release of the S100 family member S100A8 that promotes tumor progression. In sum, we describe an obesity associated cellular network of cancer cells, neutrophils and M2 polarized macrophages that promotes tumor growth.

cancer biology↗

bioRxiv2022

epialleleR: an R/BioC package for sensitive allele-specific methylation analysis in NGS data

Low-level mosaic methylation of the BRCA1 gene promoter occurs in 5-8% of healthy individuals and is associated with a significantly elevated risk of breast and ovarian cancer. Similar events may also affect other tumour suppressor genes, potentially being a significant contributor to cancer burden. While this opens a new area for translational research, detection of low-level mosaic epigenetic events requires highly sensitive and robust methodology for methylation analysis. We here present epialleleR, a computational framework for sensitive detection, quantification and visualisation of mosaic epimutations in methylation sequencing data. Analysing simulated and real data sets, we provide in-depth assessments of epialleleR performance, and show that linkage to epihaplotype data is necessary to detect low-level methylation events. The epialleleR is freely available at https://github.com/BBCG/epialleleR and https://bioconductor.org/packages/epialleleR/ as an open source R/Bioconductor package.

bioinformatics↗

bioRxiv2020

Bortezomib abrogates temozolomide-induced autophagic flux through an ATG5 dependent pathway

Glioblastoma (GBM) is invariably resistant to temozolomide (TMZ) chemotherapy. Inhibiting the proteasomal pathway is an emerging strategy to accumulate damaged proteins and inhibit their lysosomal degradation. We hypothesized that bortezomib (BTZ) might sensitize GBM cells to TMZ. We examined change in autophagic flux after drug treatments and in combination with pharmacological inhibitors or CRISPR cas9 knockout of autophagy-related genes -5 and -7 (ATG5 and ATG7, respectively). Autophagic flux was increased in temozolomide resistant GBM cells as indicated by diminished levels of the autophagy markers LC3A/B-II and p62(SQSTM1), increased localisation of LC3A/B-II with STX17, higher long-lived protein degradation and no induction of apoptosis. In contrast, BTZ treatment abrogated autophagic flux by accumulation of LC3A/B-II and p62(SQSTM1) positive autophagosomes that did not fuse with lysosomes and reduced degradation of long-lived proteins. BTZ synergistically enhanced TMZ efficacy by attenuating cell proliferation, increased DNA damage and apoptosis. CRISPR Cas ATG5 knockout reversed BTZ-induced autophagy blockade and rescued the GBM treated cells from death. We conclude that bortezomib abrogates temozolomide induced autophagy through ATG5 dependent pathway.

cancer biology↗

bioRxiv2020

ramr: an R package for detection of rare aberrantly methylated regions

MotivationWith recent advances in the field of epigenetics, the focus is widening from large and frequent disease- or phenotype-related methylation signatures to rare alterations transmitted mitotically or transgenerationally (constitutional epimutations). Merging evidence indicate that such constitutional alterations, albeit occurring at a low mosaic level, may confer risk of disease later in life. Given their inherently low incidence rate and mosaic nature, there is a need for bioinformatic tools specifically designed to analyse such events. ResultsWe have developed a method (ramr) to identify aberrantly methylated DNA regions (AMRs). ramr can be applied to methylation data obtained by array or next-generation sequencing techniques to discover AMRs being associated with elevated risk of cancer as well as other diseases. We assessed accuracy and performance metrics of ramr and confirmed its applicability for analysis of large public data sets. Using ramr we identified aberrantly methylated regions that are known or may potentially be associated with development of colorectal cancer and provided functional annotation of AMRs that arise at early developmental stages. Availability and implementationThe R package is freely available at https://github.com/BBCG/ramr

bioinformatics↗

bioRxiv2020

C/EBPB-dependent Adaptation to Palmitic Acid Promotes Stemness in Hormone Receptor Negative Breast Cancer

Epidemiological studies have established a positive association between obesity and the incidence of postmenopausal breast cancer. Moreover, it is known that obesity promotes stem cell-like properties of breast cancer cells. However, the cancer cell-autonomous mechanisms underlying this correlation are not well defined. Here we demonstrate that obesity-associated tumor formation is driven by cellular adaptation rather than expansion of pre-existing clones within the cancer cell population. While there is no correlation with specific mutations, cellular adaptation to obesity is governed by palmitic acid (PA) and leads to enhanced tumor formation capacity of breast cancer cells. This process is governed epigenetically through increased chromatin occupancy of the transcription factor CCAAT/enhancer-binding protein beta (C/EBPB). Obesity-induced epigenetic activation of C/EBPB regulates cancer stem-like properties by modulating the expression of key downstream regulators including CLDN1 and LCN2. Collectively, our findings demonstrate that obesity drives cellular adaptation to PA drives tumor initiation in the obese setting through activation of a C/EBPB dependent transcriptional network. SignificanceCellular adaptation to obesity-induced palmitic acid drives tumor initiation through activation of a C/EBPB-dependent transcriptional network. This highlights a cell-autonomous mechanistic connection between obesity and postmenopausal hormone receptor negative breast cancer.

cancer biology↗

bioRxiv2019

The novel microRNAs hsa-miR-nov7 and hsa-miR-nov3 are over-expressed in locally advanced breast cancer

miRNAs are an important class of small non-coding RNAs, which play a versatile role in gene regulation at the post-transcriptional level. Expression of miRNAs is often deregulated in human cancers.\n\nWe analyzed small RNA massive parallel sequencing data from 50 locally advanced breast cancers aiming to identify novel breast cancer related miRNAs. We successfully predicted 10 novel miRNAs, out of which 2 (hsa-miR-nov3 and hsa-miR-nov7) were recurrent. Applying high sensitivity qPCR, we detected these two microRNAs in 206 and 214 out of 223 patients in the study from which the initial cohort of 50 samples were drawn. We found hsa-miR-nov3 and hsa-miR-nov7 both to be overexpressed in tumor versus normal breast tissue in a separate set of 13 patients (p=0.009 and p=0.016, respectively) from whom both tumor tissue and normal tissue were available. We observed hsa-miR-nov3 to be expressed at higher levels in ER-positive compared to ER-negative tumors (p=0.037). Further stratifications revealed particularly low levels in the her2-like and basal-like cancers compared to other subtypes (p=0.009 and 0.040, respectively).\n\nWe predicted target genes for the 2 microRNAs and identified inversely correlated genes in mRNA expression array data available from 203 out of the 223 patients. Applying the KEGG and GO annotations to target genes revealed pathways essential to cell development, communication and homeostasis.\n\nAlthough a weak association between high expression levels of hsa-miR-nov7 and poor survival was observed, this did not reach statistical significance. hsa-miR-nov3 expression levels had no impact on patient survival.

molecular biology↗

bioRxiv2019

Golgi-localized PAQR4 mediates Anti-apoptotic Ceramidase Activity in Breast Cancer

The metabolic network of sphingolipids plays important roles in cancer biology. Prominent sphingolipids include ceramides and sphingosine-1-phosphate that regulate multiple aspects of growth, apoptosis and cellular signaling. Although many significant enzymatic regulators of the sphingolipid pathway have been described in detail, the list is currently incomplete. Here, we applied a systemic approach to identify and molecularly define progestin and adipoQ receptor family member IV (PAQR4) as a Golgi-localized ceramidase. We find PAQR4 to be [~]5 fold upregulated in breast cancer compared to matched control tissue and that its overexpression correlate with disease-specific survival rates in breast cancer. PAQR4 is a seven transmembrane protein, and depletion of PAQR4 leads to cellular apoptosis through accumulation of ceramides. Our findings establish PAQR4 as Golgi-localized ceramidase required for cellular growth in breast cancer.

cancer biology↗