Post-transcriptional deregulation is a defining feature of metastatic cancer. While many microRNAs have been implicated as regulators of metastatic progression, less is known about the roles and ...mechanisms of RNA-binding proteins in this process. We identified muscleblind-like 1 (MBNL1), a gene implicated in myotonic dystrophy, as a robust suppressor of multiorgan breast cancer metastasis. MBNL1 binds the 3' untranslated regions (UTRs) of DBNL (drebrin-like protein) and TACC1 (transforming acidic coiled-coil containing protein 1)-two genes that we implicate as metastasis suppressors. By enhancing the stability of these genes' transcripts, MBNL1 suppresses cell invasiveness. Consistent with these findings, elevated MBNL1 expression in human breast tumors is associated with reduced metastatic relapse likelihood. Our findings delineate a post-transcriptional network that governs breast cancer metastasis through RNA-binding protein-mediated transcript stabilization.
Interferon signaling mediates resistance to immune checkpoint blockade therapy, but the underlying mechanisms are poorly understood. In this issue of Immunity, Cucolo et al. identify RIPK1 as an ...interferon-stimulated gene with potent effects on cell extrinsic and intrinsic immunotherapy resistance.
Common germline variants of the APOE gene are major risk modifiers of neurodegenerative and atherosclerotic diseases
, but their effect on cancer outcome is poorly defined. Here we report that, in a ...reversal of their effect on Alzheimer's disease, the APOE4 and APOE2 variants confer favorable and poor outcomes in melanoma, respectively. Mice expressing the human APOE4 allele exhibited reduced melanoma progression and metastasis relative to APOE2 mice. APOE4 mice exhibited enhanced anti-tumor immune activation relative to APOE2 mice, and T cell depletion experiments showed that the effect of APOE genotype on melanoma progression was mediated by altered anti-tumor immunity. Consistently, patients with melanoma carrying the APOE4 variant experienced improved survival in comparison to carriers of APOE2. Notably, APOE4 mice also showed improved outcomes under PD1 immune checkpoint blockade relative to APOE2 mice, and patients carrying APOE4 experienced improved anti-PD1 immunotherapy survival after progression on frontline regimens. Finally, enhancing APOE expression via pharmacologic activation of liver X receptors, previously shown to boost anti-tumor immunity
, exhibited therapeutic efficacy in APOE4 mice but not in APOE2 mice. These findings demonstrate that pre-existing hereditary genetics can impact progression and survival outcomes of a future malignancy and warrant prospective investigation of APOE genotype as a biomarker for melanoma outcome and therapeutic response.
Altered abundance of phosphatidyl inositides (PIs) is a feature of cancer. Various PIs mark the identity of diverse membranes in normal and malignant cells. Phosphatidylinositol 4,5‐bisphosphate ...(PI(4,5)P2) resides predominantly in the plasma membrane, where it regulates cellular processes by recruiting, activating, or inhibiting proteins at the plasma membrane. We find that PTPRN2 and PLCβ1 enzymatically reduce plasma membrane PI(4,5)P2 levels in metastatic breast cancer cells through two independent mechanisms. These genes are upregulated in highly metastatic breast cancer cells, and their increased expression associates with human metastatic relapse. Reduction in plasma membrane PI(4,5)P2 abundance by these enzymes releases the PI(4,5)P2‐binding protein cofilin from its inactive membrane‐associated state into the cytoplasm where it mediates actin turnover dynamics, thereby enhancing cellular migration and metastatic capacity. Our findings reveal an enzymatic network that regulates metastatic cell migration through lipid‐dependent sequestration of an actin‐remodeling factor.
Synopsis
The phosphatidylinositol phosphatase activity harboring protein tyrosine phosphatase PTPRN2 and the phospholipase PLCβ1 are overexpressed in breast cancer. Both enzymes reduce plasma membrane PI(4,5)P2 levels, thereby enhancing cofilin‐mediated actin remodeling and breast cancer metastasis.
Increased expression of PTPRN2 and PLCβ1 clinically correlates with breast cancer metastasis.
PTPRN2 and PLCβ1 promote breast cancer cell migration.
PTPRN2 and PLCβ1 modulate plasma membrane PI(4,5)P2 levels to promote actin remodeling.
The phosphatidylinositol phosphatase activity harboring protein tyrosine phosphatase PTPRN2 and the phospholipase PLCβ1 are overexpressed in breast cancer. Both enzymes reduce plasma membrane PI(4,5)P2 levels, thereby enhancing cofilin‐mediated actin remodeling and breast cancer metastasis.
A search for general regulators of cancer metastasis has yielded a set of microRNAs for which expression is specifically lost as human breast cancer cells develop metastatic potential. Here we show ...that restoring the expression of these microRNAs in malignant cells suppresses lung and bone metastasis by human cancer cells in vivo. Of these microRNAs, miR-126 restoration reduces overall tumour growth and proliferation, whereas miR-335 inhibits metastatic cell invasion. miR-335 regulates a set of genes whose collective expression in a large cohort of human tumours is associated with risk of distal metastasis. miR-335 suppresses metastasis and migration through targeting of the progenitor cell transcription factor SOX4 and extracellular matrix component tenascin C. Expression of miR-126 and miR-335 is lost in the majority of primary breast tumours from patients who relapse, and the loss of expression of either microRNA is associated with poor distal metastasis-free survival. miR-335 and miR-126 are thus identified as metastasis suppressor microRNAs in human breast cancer.
Mutations in the TSC1 or TSC2 tumor suppressor genes lead to tuberous sclerosis complex (TSC), a dominant hamartomatous disorder that often presents with mental retardation, epilepsy and autism. The ...etiology of these neurological symptoms is unclear and the function of the TSC pathway in neurons is unknown. We found that in post-mitotic, hippocampal pyramidal neurons of mice and rats, loss of Tsc1 or Tsc2 triggered enlargement of somas and dendritic spines and altered the properties of glutamatergic synapses. Furthermore, loss of a single copy of the Tsc1 gene was sufficient to perturb dendritic spine structure. Morphological changes required regulation of the actin-depolymerization factor cofilin at a conserved LIM-kinase phosphorylation site, the phosphorylation of which was increased by loss of Tsc2. Thus, the TSC pathway regulates growth and synapse function in neurons, and perturbations of neuronal structure and function are likely to contribute to the pathogenesis of the neurological symptoms of TSC.
Cancer cells need to acquire specific molecular traits in order to spread to distant organs. In this issue of Developmental Cell, Marsh et al. show that autophagy restricts the outgrowth of breast ...cancer metastases in contrast to its impact on primary tumor progression.
Cancer cells need to acquire specific molecular traits in order to spread to distant organs. In this issue of Developmental Cell, Marsh et al. show that autophagy restricts the outgrowth of breast cancer metastases in contrast to its impact on primary tumor progression.
Through in vivo selection of multiple ER-negative human breast cancer populations for enhanced tumour-forming capacity, we have derived subpopulations that generate tumours more efficiently than ...their parental populations at low cell numbers. Tumorigenic-enriched subpopulations exhibited increased expression of LAMA4, FOXQ1 and NAP1L3—genes that are also expressed at greater levels by independently derived metastatic subpopulations. These genes promote metastatic efficiency. FOXQ1 promotes LAMA4 expression, and LAMA4 enhances clonal expansion following substratum detachment in vitro, tumour re-initiation in multiple organs, and disseminated metastatic cell proliferation and colonization. The promotion of cancer cell proliferation and tumour re-initiation by LAMA4 requires β1-integrin. Increased LAMA4 expression marks the transition of human pre-malignant breast lesions to malignant carcinomas, and tumoral LAMA4 overexpression predicts reduced relapse-free survival in ER-negative patients. Our findings reveal common features that govern primary and metastatic tumour re-initiation and identify a key molecular determinant of these processes.
Post-transcriptional regulators have emerged as robust effectors of metastasis and display deregulated expression through unknown mechanisms. Here, we reveal that the human microRNA-335 locus ...undergoes genetic deletion and epigenetic promoter hypermethylation in every metastatic derivative obtained from independent patients' malignant cell populations. Genetic deletion of miR-335 is a common event in human breast cancer, is enriched for in breast cancer metastases, and also correlates with ovarian cancer recurrence. We furthermore identify miR-335 as a robust inhibitor of tumor reinitiation. We thus implicate the miR-335 locus on 7q32.2 as the first selective metastasis suppressor and tumor initiation suppressor locus in human breast cancer.
PDF
