The Sprouty/Spred family as tumor suppressors: Coming of age

Knockdown of miR-1293 attenuates lung adenocarcinoma angiogenesis via Spry4 upregulation-mediated ERK1/2 signaling inhibition

Lung adenocarcinoma (LUAD) is the most common histologic subtype of lung cancer. Angiogenesis plays a pivotal role in LUAD progression via supplying oxygen and nutrients for cancer cells. Non-coding miR-1293, a significantly up-regulated miRNA in LUAD tissues, can be potentially used as a novel biomarker for predicting the prognosis of LUAD patients. However, little information is available about the function of miR-1293 in LUAD progression especially cancer-induced angiogenesis. Herein, we found that miR-1293 knockdown could obviously attenuate LUAD-induced angiogenesis in vitro and down-regulate two most important pro-angiogenic cytokines VEGF-A and bFGF expression and secretion. Indeed, miR-1293 abrogation inactivated the angiogenesis-promoting ERK1/2 signaling characterized by decreased ERK1/2 phosphorylation and translocation from nucleus to cytoplasm. Next we found that miR-1293 knockdown reactivated the endogenous ERK1/2 pathway inhibitor Spry4 expression and Spry4 perturbance with specific siRNA transfection abolished the inhibition of ERK1/2 pathway and LUAD-induced angiogenesis by miR-1293 knockdown. Finally, with in vivo assay, we found obvious Spry4 up-regulation and VEGF-A, bFGF, ERK1/2 phosphorylation, micro-vessel density marker CD31 expression down-regulation in vivo, respectively. Collectively, these results indicated that miR-1293 knockdown could significantly attenuate LUAD angiogenesis via Spry4-mediated ERK1/2 signaling inhibition, which might be helpful for uncovering more functions of miR-1293 in LUAD and providing experimental basis for possible LUAD therapeutic strategy targeting miR-1293.

MEK inhibitors and DA-Raf, a dominant-negative antagonist of the Ras-ERK pathway, prevent the migration and invasion of KRAS-mutant cancer cells

The Ras-induced ERK pathway (Raf-MEK-ERK signaling cascade) regulates a variety of cellular responses including cell proliferation, survival, and migration. Activating mutations in RAS genes, particularly in the KRAS gene, constitutively activate the ERK pathway, resulting in tumorigenesis, cancer cell invasion, and metastasis. DA-Raf1 (DA-Raf) is a splicing isoform of A-Raf and contains the Ras-binding domain but lacks the kinase domain. Consequently, DA-Raf antagonizes the Ras-ERK pathway in a dominant-negative manner and can serve as a tumor suppressor that targets mutant Ras protein-induced tumorigenesis. We show here that MEK inhibitors and DA-Raf interfere with the in vitro collective cell migration and invasion of human KRAS-mutant carcinoma cell lines, the lung adenocarcinoma A549, colorectal carcinoma HCT116, and pancreatic carcinoma MIA PaCa-2 cells. DA-Raf expression was silenced in these cancer cell lines. All these cell lines had high collective migration abilities and invasion properties in Matrigel, compared with nontumor cells. Their migration and invasion abilities were impaired by suppressing the ERK pathway with the MEK inhibitors U0126 and trametinib, an approved anticancer drug. Expression of DA-Raf in MIA PaCa-2 cells reduced the ERK activity and hindered the migration and invasion abilities. Therefore, DA-Raf may function as an invasion suppressor protein in the KRAS-mutant cancer cells by blocking the Ras-ERK pathway when DA-Raf expression is induced in invasive cancer cells.

Role of SPRY4 in health and disease

SPRY4 is a protein encoding gene that belongs to the Spry family. It inhibits the mitogen-activated protein kinase (MAPK) signaling pathway and plays a role in various biological functions under normal and pathological conditions. The SPRY4 protein has a specific structure and interacts with other molecules to regulate cellular behavior. It serves as a negative feedback inhibitor of the receptor protein tyrosine kinases (RTK) signaling pathway and interferes with cell proliferation and migration. SPRY4 also influences inflammation, oxidative stress, and cell apoptosis. In different types of tumors, SPRY4 can act as a tumor suppressor or an oncogene. Its dysregulation is associated with the development and progression of various cancers, including colorectal cancer, glioblastoma, hepatocellular carcinoma, perihilar cholangiocarcinoma, gastric cancer, breast cancer, and lung cancer. SPRY4 is also involved in organ development and is associated with ischemic diseases. Further research is ongoing to understand the expression and function of SPRY4 in specific tumor microenvironments and its potential as a therapeutic target.

BRAF - a tumour-agnostic drug target with lineage-specific dependencies

In June 2022, the FDA granted Accelerated Approval to the BRAF inhibitor dabrafenib in combination with the MEK inhibitor trametinib for the treatment of adult and paediatric patients (≥6 years of age) with unresectable or metastatic BRAFV600E-mutant solid tumours, except for BRAFV600E-mutant colorectal cancers. The histology-agnostic approval of dabrafenib plus trametinib marks the culmination of two decades of research into the landscape of BRAF mutations in human cancers, the biochemical mechanisms underlying BRAF-mediated tumorigenesis, and the clinical development of selective RAF and MEK inhibitors. Although the majority of patients with BRAFV600E-mutant tumours derive clinical benefit from BRAF inhibitor-based combinations, resistance to treatment develops in most. In this Review, we describe the biochemical basis for oncogenic BRAF-induced activation of MAPK signalling and pan-cancer and lineage-specific mechanisms of intrinsic, adaptive and acquired resistance to BRAF inhibitors. We also discuss novel RAF inhibitors and drug combinations designed to delay the emergence of treatment resistance and/or expand the population of patients with BRAF-mutant cancers who benefit from molecularly targeted therapies.

Ultraviolet Radiation Biological and Medical Implications

Ultraviolet (UV) radiation plays a crucial role in the development of melanoma and non-melanoma skin cancers. The types of UV radiation are differentiated by wavelength: UVA (315 to 400 nm), UVB (280 to 320 nm), and UVC (100 to 280 nm). UV radiation can cause direct DNA damage in the forms of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs). In addition, UV radiation can also cause DNA damage indirectly through photosensitization reactions caused by reactive oxygen species (ROS), which manifest as 8-hydroxy-2'-deoxyguanine (8-OHdG). Both direct and indirect DNA damage can lead to mutations in genes that promote the development of skin cancers. The development of melanoma is largely influenced by the signaling of the melanocortin one receptor (MC1R), which plays an essential role in the synthesis of melanin in the skin. UV-induced mutations in the BRAF and NRAS genes are also significant risk factors in melanoma development. UV radiation plays a significant role in basal cell carcinoma (BCC) development by causing mutations in the Hedgehog (Hh) pathway, which dysregulates cell proliferation and survival. UV radiation can also induce the development of squamous cell carcinoma via mutations in the TP53 gene and upregulation of MMPs in the stroma layer of the skin.

Oscillatory Hypoxia Can Induce Senescence of Adipose-Derived Mesenchymal Stromal Cells Potentiating Invasive Transformation of Breast Epithelial Cells

Obesity is strongly associated with occurrence, metastasis, and resistance to therapy in breast cancers, which also exhibit high adipose content in the tumor microenvironment. Adipose tissue-derived mesenchymal stromal cells (ASCs) are recruited to breast cancer by many mechanisms, including hypoxia, and contribute to metastatic transition of the cancer. Breast cancers are characterized by regions of hypoxia, which can be temporally unstable owing to a mismatch between oxygen supply and consumption. Using a high-sensitivity nanopatterned stromal invasion assay, we found that ASCs could promote stromal invasion of not only breast cancer cell lines but also MCF10A1, a cell line derived from untransformed breast epithelium. RNA sequencing of MCF10A1 cells conditioned with medium from ASCs revealed upregulation of genes associated with increased cell migration, chemotaxis, and metastasis. Furthermore, we found that fluctuating or oscillating hypoxia could induce senescence in ASCs, which could result in an increased invasive potential in the treated MCF10A1 cells. These findings highlight the complex interplay within the breast cancer microenvironment, hypoxia, and the role of ASCs in transforming even non-cancerous breast epithelium toward an invasive phenotype, providing insights into early metastatic events.

Bioinformatics analysis for the identification of Sprouty-related EVH1 domain-containing protein 3 expression and its clinical significance in thyroid carcinoma

The poorly differentiated thyroid carcinoma (THCA) subtype is associated with an aggressive disease course, a less favorable overall prognosis, and an increased risk of distant organ metastasis. In this study, our objective was to explore the potential utility of the Sprouty-related EVH1 domain-containing protein 3 (SPRED3) as a biomarker for early diagnosis and prognosis in THCA patients. The differentially expressed prognostic-related genes associated with THCA were identified by querying The Cancer Genome Atlas (TCGA) database. The difference in the expression of the SPRED3 gene between thyroid carcinoma (THCA) tissues and normal tissues was analyzed using data from The Cancer Genome Atlas (TCGA) and further validated through immunohistochemistry. Univariate and multivariate Cox regression models were used, along with clinical information from THCA patients, to analyze the prognostic value of the SPRED3 gene in THCA patients. Functional enrichment analysis was subsequently performed to elucidate the molecular mechanisms underlying the regulatory effects of the SPRED3 gene on thyroid carcinoma. Additionally, we calculated the percentage of infiltrating immune cells in THCA patients and evaluated their correlation with SPRED3 gene expression. Compared with those in noncancerous thyroid tissue, the gene and protein expression levels of SPRED3 were found to be elevated in thyroid carcinoma tissues. Furthermore, the expression of SPRED3 in thyroid carcinoma exhibited significant correlations with tumor location, histological grade, pathological stage, and tumor node metastasis classification (TNM) stage. Univariate and multivariate Cox proportional hazards (Cox) regression analyses demonstrated that SPRED3 could serve as an independent prognostic factor for predicting the overall survival of THCA patients. The results of functional enrichment analysis suggested the potential involvement of SPRED3 in the regulation of extracellular matrix organization, epidermal development, signaling receptor activator activity, skin development, receptor ligand activity, glycosaminoglycan binding, neuroactive ligand‒receptor interaction, the IL-17 signaling pathway, and the PI3K-Akt signaling pathway. Additionally, there were significant correlations between the expression level of the SPRED3 gene and the infiltration of various immune cells (eosinophils, central memory T cells, neutrophils, macrophages, and NK cells) within the thyroid tumor microenvironment. SPRED3 can be used as a prognostic biomarker in patients with THCA could potentially be therapeutic target for THCA.

Proteomic analysis of holocarboxylase synthetase deficient-MDA-MB-231 breast cancer cells revealed the biochemical changes associated with cell death, impaired growth signaling, and metabolism

We have previously shown that the holocarboxylase synthetase (HLCS) is overexpressed in breast cancer tissue of patients, and silencing of its expression in triple-negative cancer cell line inhibits growth and migration. Here we investigated the global biochemical changes associated with HLCS knockdown in MDA-MB-231 cells to discern the pathways that involve HLCS. Proteomic analysis of two independent HLCS knockdown cell lines identified 347 differentially expressed proteins (DEPs) whose expression change > 2-fold (p < 0.05) relative to the control cell line. GO enrichment analysis showed that these DEPs were mainly associated with the cellular process such as cellular metabolic process, cellular response to stimulus, and cellular component organization or biogenesis, metabolic process, biological regulation, response to stimuli, localization, and signaling. Among the 347 identified DEPs, 64 proteins were commonly found in both HLCS knockdown clones, confirming their authenticity. Validation of some of these DEPs by Western blot analysis showed that plasminogen activator inhibitor type 2 (SerpinB2) and interstitial collagenase (MMP1) were approximately 90% decreased in HLCS knockdown cells, consistent with a 50%-60% decrease in invasion ability of knockdown cells. Notably, argininosuccinate synthase 1 (ASS1), one of the enzymes in the urea cycle, showed approximately a 10-fold increase in the knockdown cells, suggesting the crucial role of HLCS in supporting the urea cycle in the triple-negative cancer cell line. Collectively, our proteomic data provide biochemical insights into how suppression of HLCS expression perturbs global changes in cellular processes and metabolic pathways, impairing cell growth and invasion.

Mapping chromatin state and transcriptional response in CIC-DUX4 undifferentiated round cell sarcoma

CIC-DUX4 is a rare and understudied transcription factor fusion oncoprotein. CIC-DUX4 co-opts native gene targets to drive a lethal form of human sarcoma. The molecular underpinnings that lead to oncogenic reprograming and CIC-DUX4 sarcomagenesis remain largely undefined. Through an integrative ChIP and RNA-Seq analysis using patient-derived CIC-DUX4 cells, we define CIC-DUX4 mediated chromatin states and function. We show that CIC-DUX4 primarily localizes to proximal and distal cis-regulatory elements where it associates with active histone marks. Our findings nominate key signaling pathways and molecular targets that enable CIC-DUX4 to mediate tumor cell survival. Collectively, our data demonstrate how the CIC-DUX4 fusion oncoprotein impacts chromatin state and transcriptional responses to drive an oncogenic program in undifferentiated sarcoma.

Significance

CIC-DUX4 sarcoma is a rare and lethal sarcoma that affects children, adolescent young adults, and adults. CIC-DUX4 sarcoma is associated with rapid metastatic dissemination and relative insensitivity to chemotherapy. There are no current standard-of-care therapies for CIC-DUX4 sarcoma leading to universally poor outcomes for patients. Through a deep mechanistic understanding of how the CIC-DUX4 fusion oncoprotein reprograms chromatin state and function, we aim to improve outcomes for CIC-DUX4 patients.

Quercetin's Dual Mode of Action to Counteract the Sp1-miR-27a Axis in Colorectal Cancer Cells

Quercetin (Qc) inhibits cell proliferation and induces apoptosis in a variety of cancer cells. The molecular mechanism of action has not been fully elucidated; however, interplay with some miRNAs has been reported, specifically with miR-27a, an onco-miRNA overexpressed in several malignancies. Here, we show that Qc reduces cell viability and induces apoptosis in HCT116 and HT-29 colon cancer cells, by upregulating negative modulators of proliferation pathways such as Sprouty2, PTEN and SFRP1. These are targets of miR-27a whose high expression is reduced by Qc. Moreover, miR-23a, and miR-24-2, the two other components of the unique gene cluster, and the pri-miRNA transcript are reduced, evoking a transcriptional regulation of the entire cluster by Sp1. Mechanistically, we show that Qc is rapidly internalized and localizes in the nucleus, where it likely interacts with Sp1, inducing its proteasomal degradation. Sp1 is further repressed by ZBTB10, an Sp1 competitor for DNA binding that is an miR-27a target and whose levels increase following Qc. SP1 mRNA is also reduced, supporting the regulation of its own gene transcription. Finally, Sp1 knockdown elicits the impaired transcription of the entire cluster and the upregulation of the miR-27a targets, phenocopying the effects of Qc. Through this dual mode of action, Qc counteracts the protumoral Sp1-miR-27a axis, opening the way for novel therapies based on its association as neoadjuvant with known anticancer treatments.

Loss of SPRY2 contributes to cancer-associated fibroblasts activation and promotes breast cancer development

The communication between tumor cells and tumor microenvironment plays a critical role in cancer development. Cancer-associated fibroblasts (CAFs) are the major components of the tumor microenvironment and take part in breast cancer formation and progression. Here, by comparing the gene expression patterns in CAFs and normal fibroblasts, we found SPRY2 expression was significantly decreased in CAFs and decreased SPRY2 expression was correlated with worse prognosis in breast cancer patients. SPRY2 knockdown in fibroblasts promoted tumor growth and distant metastasis of breast cancer in mice. Loss of stromal SPRY2 expression promoted CAF activation dependent on glycolytic metabolism. Mechanically, SPRY2 suppressed Y10 phosphorylation of LDHA and LDHA activity by interfering with the interaction between LDHA and SRC. Functionally, SPRY2 knockdown in fibroblasts enhanced the stemness of tumor cell dependent on glycolysis in fibroblasts. Collectively, this work identified SPRY2 as a negative regulator of CAF activation, and SPRY2 in CAFs may potentially be therapeutically targeted in breast cancer treatment.

Targeting HIF-1 for prostate cancer: a synthesis of preclinical evidence

INTRODUCTION

Hypoxia-inducible factor (HIF) mediates multiple intracellular processes that drive cellular metabolism and induce proliferation. Dysregulated HIF expression is associated with oncogenic cellular transformation. Moreover, high HIF levels correlate with tumor aggressiveness and chemoresistance, indicating the vital effect of HIF-1α on tumorigenicity. Currently, widespread in-vitro and in-vivo research is focusing on targeting HIF with drugs that have already been approved for use by the FDA, such as belzutifan, in renal cell carcinoma. HIF inhibition is mostly associated with tumor size reduction; however, drug toxicity remains a challenge.

AREA COVERED

In this review, we focus on the potential of targeting HIF in prostate cancer (PC) and summarize the scientific background of HIF activity in PC. This finding emphasizes the rationale for using HIF as a therapeutic target in this malignancy. We have listed known HIF inhibitors that are being investigated in preclinical studies and their potential as anticancer drugs for PC.

EXPERT OPINION

Although HIF-targeting agents have been investigated for over a decade, their use in therapy-resistant cancers remains relevant and should be explored further. In addition, the use of naturally occurring HIF inhibitors should be considered as an add-on therapy for the currently used regimens.

Increased SPRY1 expression activates NF-κB signaling and promotes pancreatic cancer progression by recruiting neutrophils and macrophages through CXCL12-CXCR4 axis

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a high mortality rate, in which about 90% of patients harbor somatic oncogenic point mutations in KRAS. SPRY family genes have been recognized as crucial negative regulators of Ras/Raf/ERK signaling. Here, we investigate the expression and role of SPRY proteins in PDAC.

METHODS

Expression of SPRY genes in human and mice PDAC was analyzed using The Cancer Genome Atlas and Gene Expression Omnibus datasets, and by immunohistochemistry analysis. Gain-of-function, loss-of-function of Spry1 and orthotopic xenograft model were adopted to investigate the function of Spry1 in mice PDAC. Bioinformatics analysis, transwell and flowcytometry analysis were used to identify the effects of SPRY1 on immune cells. Co-immunoprecipitation and K-ras4B ^G12V overexpression were used to identify molecular mechanism.

RESULTS

SPRY1 expression was remarkably increased in PDAC tissues and positively associated with poor prognosis of PDAC patients. SPRY1 knockdown suppressed tumor growth in mice. SPRY1 was found to promote CXCL12 expression and facilitate neutrophil and macrophage infiltration via CXCL12-CXCR4 axis. Pharmacological inhibition of CXCL12-CXCR4 largely abrogated the oncogenic functions of SPRY1 by suppressing neutrophil and macrophage infiltration. Mechanistically, SPRY1 interacted with ubiquitin carboxy-terminal hydrolase L1 to induce activation of nuclear factor κB signaling and ultimately increase CXCL12 expression. Moreover, SPRY1 transcription was dependent on KRAS mutation and was mediated by MAPK-ERK signaling.

CONCLUSION

High expression of SPRY1 can function as an oncogene in PDAC by promoting cancer-associated inflammation. Targeting SPRY1 might be an important approach for designing new strategy of tumor therapy.

Adaptive and non-adaptive gene expression responses in prostate cancer during androgen deprivation

Androgen deprivation therapy is the cornerstone treatment of advanced prostate cancer. Eventually prostate cancer cells overcome androgen deprivation therapy, giving rise to castration resistant prostate cancer (CRPC) characterized by increased androgen receptor (AR) activity. Understanding the cellular mechanisms leading to CRPC is needed for development of novel treatments. We used long-term cell cultures to model CRPC; a testosterone-dependent cell line (VCaP-T) and cell line adapted to grow in low testosterone (VCaP-CT). These were used to uncover persistent and adaptive responses to testosterone level. RNA was sequenced to study AR-regulated genes. Expression level changed due to testosterone depletion in 418 genes in VCaP-T (AR-associated genes). To evaluate significance for CRPC growth, we compared which of them were adaptive i.e., restored expression level in VCaP-CT. Adaptive genes were enriched to steroid metabolism, immune response and lipid metabolism. The Cancer Genome Atlas Prostate Adenocarcinoma data were used to assess the association with cancer aggressiveness and progression-free survival. Expressions of 47 AR-associated or association gaining genes were statistically significant markers for progression-free survival. These included genes related to immune response, adhesion and transport. Taken together, we identified and clinically validated multiple genes being linked with progression of prostate cancer and propose several novel risk genes. Possible use as biomarkers or therapeutic targets should be studied further.

Feedback Regulation of Signaling Pathways for Precise Pre-Placodal Ectoderm Formation in Vertebrate Embryos

Intracellular signaling pathways are essential to establish embryonic patterning, including embryonic axis formation. Ectodermal patterning is also governed by a series of morphogens. Four ectodermal regions are thought to be controlled by morphogen gradients, but some perturbations are expected to occur during dynamic morphogenetic movement. Therefore, a mechanism to define areas precisely and reproducibly in embryos, including feedback regulation of signaling pathways, is necessary. In this review, we outline ectoderm pattern formation and signaling pathways involved in the establishment of the pre-placodal ectoderm (PPE). We also provide an example of feedback regulation of signaling pathways for robust formation of the PPE, showing the importance of this regulation.

ERK2 signaling regulates cell-cell adhesion of epithelial cells and enhances growth factor-induced cell scattering

The ERK signaling pathway, consisting of core protein kinases Raf, MEK and effector kinases ERK1/2, regulates various biological outcomes such as cell proliferation, differentiation, apoptosis, or cell migration. Signal transduction through the ERK signaling pathway is tightly controlled at all levels of the pathway. However, it is not well understood whether ERK pathway signaling can be modulated by the abundance of ERK pathway core kinases. In this study, we investigated the effects of low-level overexpression of the ERK2 isoform on the phenotype and scattering of cuboidal MDCK epithelial cells growing in discrete multicellular clusters. We show that ERK2 overexpression reduced the vertical size of lateral membranes that contain cell-cell adhesion complexes. Consequently, ERK2 overexpressing cells were unable to develop cuboidal shape, remained flat with increased spread area and intercellular adhesive contacts were present only on the basal side. Interestingly, ERK2 overexpression was not sufficient to increase phosphorylation of multiple downstream targets including transcription factors and induce global changes in gene expression, namely to increase the expression of pro-migratory transcription factor Fra1. However, ERK2 overexpression enhanced HGF/SF-induced cell scattering as these cells scattered more rapidly and to a greater extent than parental cells. Our results suggest that an increase in ERK2 expression primarily reduces cell-cell cohesion and that weakened intercellular adhesion synergizes with upstream signaling in the conversion of the multicellular epithelium into single migrating cells. This mechanism may be clinically relevant as the analysis of clinical data revealed that in one type of cancer, pancreatic adenocarcinoma, ERK2 overexpression correlates with a worse prognosis.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Methylation of SPRED1: A New Target in Acute Myeloid Leukemia

Sprouty-related, EVH1 domain-containing protein 1 (SPRED1) has been identified as a novel tumor suppressor gene in acute myeloid leukemia (AML). Previous studies showed that SPRED1 methylation levels were significantly increased in AML patients, making it an interesting candidate for further investigations. To confirm the association of SPRED1 methylation, clinical parameters, and known molecular prognosticators and to identify the impact of methylation level on treatment outcome, we conducted this study in a larger cohort of 75 AML patients. Significantly increased methylation levels of SPRED1 were detected at four of ten CpG units by quantitative high-resolution mass spectrometry-based approach (MassARRAY) in AML patients. Whereas overall survival (OS) and relapse-free survival (RFS) showed no statistical difference between hypermethylation and hypomethylation subgroups, the relationship between methylation level and treatment response was indicated in paired samples from pre- and post-induction. To determine the possible mechanism of SPRED1 methylation in AML, we performed in vitro experiments using THP-1 cells, as the latter showed the highest methylation level (determined by utilizing bisulfite modification) among the three AML cell lines we tested. When treated with 5-AZA and lentivirus transfection, upregulated SPRED1 expression, decreased cell proliferation, increased cell differentiation and apoptosis, and inactivated phosphorylated extracellular signal-regulated kinase (p-ERK) were detected in THP-1 cells. These results show that demethylation of SPRED1 can inhibit the proliferation of AML cells and promote their differentiation and apoptosis, possibly by the ERK pathway. The hypermethylation of SPRED1 is a potential therapeutic target for AML.

Hyperactivation of MAPK Induces Tamoxifen Resistance in SPRED2-Deficient ERα-Positive Breast Cancer

Simple Summary

Tamoxifen has been used for more than 40 years to treat breast tumors that are dependent on the hormone estrogen for their growth. However, resistance and recurrence of the tumors during the course of the treatment are common. Understanding the mechanisms that drive tamoxifen resistance and discovering new biomarkers for early detection are keys for designing appropriate personalized therapies. Here, we show that low levels of SPRED2 may be useful as a novel biomarker of tamoxifen resistance. We found that SPRED2 deficiency causes a hyperactivation of the mitogen-activated protein kinases (MAPKs) ERK1/ERK2, which in turn enhances estrogen signaling and diminishes the toxic effects of tamoxifen on breast cancer cells. Treatment with the ERK1/2 inhibitor, ulixertinib, could restore their sensitivity to tamoxifen. Therefore, we propose that patients with estrogen-dependent breast cancer characterized by low expression levels of SPRED2 may be candidates for a combination therapy with tamoxifen and ulixertinib.

Abstract

Breast cancer is the number one cause of cancer-related mortality in women worldwide. Most breast tumors depend on the expression of the estrogen receptor α (ERα) for their growth. For this reason, targeting ERα with antagonists such as tamoxifen is the therapy of choice for most patients. Although initially responsive to tamoxifen, about 40% of the patients will develop resistance and ultimately a recurrence of the disease. Thus, finding new biomarkers and therapeutic approaches to treatment-resistant tumors is of high significance. SPRED2, an inhibitor of the MAPK signal transduction pathway, has been found to be downregulated in various cancers. In the present study, we found that SPRED2 is downregulated in a large proportion of breast-cancer patients. Moreover, the knockdown of SPRED2 significantly increases cell proliferation and leads to tamoxifen resistance of breast-cancer cells that are initially tamoxifen-sensitive. We found that resistance occurs through increased activation of the MAPKs ERK1/ERK2, which enhances the transcriptional activity of ERα. Treatment of SPRED2-deficient breast cancer cells with a combination of the ERK 1/2 inhibitor ulixertinib and 4-hydroxytamoxifen (4-OHT) can inhibit cell growth and proliferation and overcome the induced tamoxifen resistance. Taken together, these results indicate that SPRED2 may also be a tumor suppressor for breast cancer and that it is a key regulator of cellular sensitivity to 4-OHT.

Spred1 deficit promotes treatment resistance and transformation of chronic phase CML

Spred1 is highly expressed in normal hematopoietic stem cells (HSCs). Lack of Spred1 function has been associated with aberrant hematopoiesis and acute leukemias. In chronic myelogenous leukemia (CML), Spred1 is reduced in patients with accelerated phase (AP) or blast crisis (BC) CML, thereby suggesting that deficit of this protein may contribute to disease transformation. In fact, Spred1 knockout (KO) in SCLtTA/BCR-ABL CML mice either globally, or restricted to hematopoietic cells (i.e., HSCs) or to endothelial cells (ECs), led to transformation of chronic phase (CP) CML into AP/BC CML. Upon BCR-ABL induction, all three Spred1 KO CML models showed AP/BC features. However, compared with global Spred1 KO, the AP/BC phenotypes of HSC-Spred1 KO and EC-Spred1 KO CML models were attenuated, suggesting a concurrent contribution of Spred1 deficit in multiple compartments of the leukemic bone marrow niche to the CML transformation. Spred1 KO, regardless if occurred in HSCs or in ECs, increased miR-126 in LSKs (Lin-Sca-1+c-Kit+), a population enriched in leukemic stem cells (LSCs), resulting in expansion of LSCs, likely through hyperactivation of the MAPK/ERK pathway that augmented Bcl-2 expression and stability. This ultimately led to enhancement of Bcl-2-dependent oxidative phosphorylation that supported homeostasis, survival and activity of LSCs and drove AP/BC transformation.

Dysregulated expression and functions of microRNA-330 in cancers: A potential therapeutic target

As small non-coding RNAs, MicroRNAs (miRNAs) bind to the 3' untranslated region (3'-UTR) of mRNA targets to control gene transcription and translation. The gene of miR-330 has two miRNA products, including miR-330-3p and miR-330-5p, which exhibit anti-tumorigenesis and/or pro-tumorigenesis effects in many kinds of malignancies. In cancers, miR-330-3p and miR-330-5p aberrant expression can influence many malignancy-related processes such as cell proliferation, migration, invasion, apoptosis and epithelial-mesenchymal transition, as well as angiogenesis and responsiveness to treatment. In many cancer types (such as lung, prostate, gastric, breast, bladder, ovarian, colorectal, and pancreatic cancer, and osteosarcoma), miR-330-5p acts as an anti-tumor agent. These cancers have low levels of miR-330-5p that leads to the upregulation of the tumor promotor target genes leading to tumor progression. Here, overexpression of miR-330-5p using miRNA inducers can prevent tumor development. Dual roles of miR-330-5p have been also indicated in the thyroid, liver and cervical cancers. Moreover, miR-330-3p exhibits pro-tumorigenesis effects in lung cancer, pancreatic cancer, osteosarcoma, bladder cancer, and cervical cancer. Here, downregulation of miR-330-3p using miRNA inhibitors can prevent tumor development. Demonstrated in breast and liver cancers, miR-330-3p also has dual roles. Importantly, the activities of miR-330-3p and/or miR-330-5p are regulated by upstream regulators long non-coding RNAs (lncRNAs), including circular and linear lncRNAs. This review comprehensively explained miR-330-3p and miR-330-5p role in development of cancers, while highlighting their downstream target genes and upstream regulators as well as possible therapeutic strategies.

SPRED2 loss-of-function causes a recessive Noonan syndrome-like phenotype

Upregulated signal flow through RAS and the mitogen-associated protein kinase (MAPK) cascade is the unifying mechanistic theme of the RASopathies, a family of disorders affecting development and growth. Pathogenic variants in more than 20 genes have been causally linked to RASopathies, the majority having a dominant role in promoting enhanced signaling. Here, we report that SPRED2 loss of function is causally linked to a recessive phenotype evocative of Noonan syndrome. Homozygosity for three different variants-c.187C>T (p.Arg63^∗), c.299T>C (p.Leu100Pro), and c.1142_1143delTT (p.Leu381Hisfs^∗95)-were identified in four subjects from three families. All variants severely affected protein stability, causing accelerated degradation, and variably perturbed SPRED2 functional behavior. When overexpressed in cells, all variants were unable to negatively modulate EGF-promoted RAF1, MEK, and ERK phosphorylation, and time-course experiments in primary fibroblasts (p.Leu100Pro and p.Leu381Hisfs^∗95) documented an increased and prolonged activation of the MAPK cascade in response to EGF stimulation. Morpholino-mediated knockdown of spred2a and spred2b in zebrafish induced defects in convergence and extension cell movements indicating upregulated RAS-MAPK signaling, which were rescued by expressing wild-type SPRED2 but not the SPRED2^{Leu381Hisfs∗95} protein. The clinical phenotype of the four affected individuals included developmental delay, intellectual disability, cardiac defects, short stature, skeletal anomalies, and a typical facial gestalt as major features, without the occurrence of the distinctive skin signs characterizing Legius syndrome. These features, in part, characterize the phenotype of Spred2^-/- mice. Our findings identify the second recessive form of Noonan syndrome and document pleiotropic consequences of SPRED2 loss of function in development.

A disease network-based deep learning approach for characterizing melanoma

Multiple types of genomic variations are present in cutaneous melanoma and some of the genomic features may have an impact on the prognosis of the disease. The access to genomics data via public repositories such as The Cancer Genome Atlas (TCGA) allows for a better understanding of melanoma at the molecular level, therefore making characterization of substantial heterogeneity in melanoma patients possible. Here, we proposed an approach that integrates genomics data, a disease network, and a deep learning model to classify melanoma patients for prognosis, assess the impact of genomic features on the classification and provide interpretation to the impactful features. We integrated genomics data into a melanoma network and applied an autoencoder model to identify subgroups in TCGA melanoma patients. The model utilizes communities identified in the network to effectively reduce the dimensionality of genomics data into a patient score profile. Based on the score profile, we identified three patient subtypes that show different survival times. Furthermore, we quantified and ranked the impact of genomic features on the patient score profile using a machine-learning technique. Follow-up analysis of the top-ranking features provided us with the biological interpretation of them at both pathway and molecular levels, such as their mutation and interactome profiles in melanoma and their involvement in pathways associated with signaling transduction, immune system and cell cycle. Taken together, we demonstrated the ability of the approach to identify disease subgroups using a deep learning model that captures the most relevant information of genomics data in the melanoma network.

Progress on Ras/MAPK Signaling Research and Targeting in Blood and Solid Cancers

Simple Summary

The Ras-Raf-MEK-ERK signaling pathway is responsible for regulating cell proliferation, differentiation, and survival. Overexpression and overactivation of members within the signaling cascade have been observed in many solid and blood cancers. Research often focuses on targeting the pathway to disrupt cancer initiation and progression. We aimed to provide an overview of the pathway’s physiologic role and regulation, interactions with other pathways involved in cancer development, and mutations that lead to malignancy. Several blood and solid cancers are analyzed to illustrate the impact of the pathway’s dysregulation, stemming from mutation or viral induction. Finally, we summarized different approaches to targeting the pathway and the associated novel treatments being researched or having recently achieved approval.

Abstract

The mitogen-activated protein kinase (MAPK) pathway, consisting of the Ras-Raf-MEK-ERK signaling cascade, regulates genes that control cellular development, differentiation, proliferation, and apoptosis. Within the cascade, multiple isoforms of Ras and Raf each display differences in functionality, efficiency, and, critically, oncogenic potential. According to the NCI, over 30% of all human cancers are driven by Ras genes. This dysfunctional signaling is implicated in a wide variety of leukemias and solid tumors, both with and without viral etiology. Due to the strong evidence of Ras-Raf involvement in tumorigenesis, many have attempted to target the cascade to treat these malignancies. Decades of unsuccessful experimentation had deemed Ras undruggable, but recently, the approval of Sotorasib as the first ever KRas inhibitor represents a monumental breakthrough. This advancement is not without novel challenges. As a G12C mutant-specific drug, it also represents the issue of drug target specificity within Ras pathway; not only do many drugs only affect single mutational profiles, with few pan-inhibitor exceptions, tumor genetic heterogeneity may give rise to drug-resistant profiles. Furthermore, significant challenges in targeting downstream Raf, especially the BRaf isoform, lie in the paradoxical activation of wild-type BRaf by BRaf mutant inhibitors. This literature review will delineate the mechanisms of Ras signaling in the MAPK pathway and its possible oncogenic mutations, illustrate how specific mutations affect the pathogenesis of specific cancers, and compare available and in-development treatments targeting the Ras pathway.

The EGFRvIII transcriptome in glioblastoma, a meta-omics analysis

Background

EGFR is among the genes most frequently altered in glioblastoma, with exons 2-7 deletions (EGFRvIII) being among its most common genomic mutations. There are conflicting reports about its prognostic role and it remains unclear whether and how it differs in signaling compared with wildtype EGFR.

Methods

To better understand the oncogenic role of EGFRvIII, we leveraged 4 large datasets into 1 large glioblastoma transcriptome dataset (n = 741) alongside 81 whole-genome samples from 2 datasets.

Results

The EGFRvIII/EGFR expression ratios differ strongly between tumors and range from 1% to 95%. Interestingly, the slope of relative EGFRvIII expression is near-linear, which argues against a more positive selection pressure than EGFR wildtype. An absence of selection pressure is also suggested by the similar survival between EGFRvIII-positive and -negative glioblastoma patients. EGFRvIII levels are inversely correlated with pan-EGFR (all wildtype and mutant variants) expression, which indicates that EGFRvIII has a higher potency in downstream pathway activation. EGFRvIII-positive glioblastomas have a lower CDK4 or MDM2 amplification incidence than EGFRvIII-negative (P = .007), which may point toward crosstalk between these pathways. EGFRvIII-expressing tumors have an upregulation of “classical” subtype genes compared to those with EGFR-amplification only (P = 3.873e⁻⁶). Genomic breakpoints of the EGFRvIII deletions have a preference toward the 3′-end of the large intron-1. These preferred breakpoints preserve a cryptic exon resulting in a novel EGFRvIII variant and preserve an intronic enhancer.

Conclusions

These data provide deeper insights into the complex EGFRvIII biology and provide new insights for targeting EGFRvIII mutated tumors.

Thrombin aggravates hypoxia/reoxygenation injury of astrocytes by activating the autophagy pathway mediated by SPRED2

Autophagy plays an important role in ischemia/reperfusion brain injury, however, the signaling pathways involved in cell autophagy are not fully understood. The present study aimed to investigate the roles and molecular mechanisms of thrombin and Sprouty-related EVH1 domain-2 (SPRED2) on autophagy in hypoxia/reoxygenation (H/R) induced astrocytes. Reverse transcription-quantitative PCR and western blot analyses were performed to detect the expression levels of thrombin and SPRED2. Western blot analysis was also performed to detect the protein expression levels of Beclin 1, microtubule-associated protein light chain 3 (LC3)-II and LC3-I. The MTT assay was performed to assess cell viability, while ELISA was performed to determine the supernatant levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α. The results demonstrated that the effects of H/R induction on inflammatory factor secretion, oxidative stress, autophagy and cell viability in astrocytes were aggravated by thrombin, the effects of which were reversed following SPRED2 knockdown. Taken together, the results of the present study suggest that thrombin aggravates H/R injury in astrocytes by activating the SPRED2-mediated autophagy.

Multi-Platform Classification of IDH-Wild-Type Glioblastoma Based on ERK/MAPK Pathway: Diagnostic, Prognostic and Therapeutic Implications

Glioblastoma is the most aggressive and frequent glioma in the adult population. Because current therapy regimens confer only minimal survival benefit, molecular subgrouping to stratify patient prognosis and therapy design is warranted. This study presents a multi-platform classification of glioblastoma by analyzing a large, ethnicity-inclusive 101-adult-patient cohort. It defines seven non-redundant IDH-wild-type glioblastoma molecular subgroups, G1-G7, corresponding to the upstream receptor tyrosine kinase (RTK) and RAS-RAF segment of the ERK/MAPK signal transduction pathway. These glioblastoma molecular subgroups are classified as G1/EGFR, G2/FGFR3, G3/NF1, G4/RAF, G5/PDGFRA, G6/Multi-RTK, and G7/Other. The comprehensive genomic analysis was refined by expression landscaping of all RTK genes, as well as of the major associated growth pathway mediators, and used to hierarchically cluster the subgroups. Parallel demographic, clinical, and histologic pattern analyses were merged with the molecular subgrouping to yield the first inclusive multi-platform classification for IDH-wild-type glioblastoma. This straightforward classification with diagnostic and prognostic significance may be readily used in neuro-oncological practice and lays the foundation for personalized targeted therapy approaches.

miR-19 Promotes Cell Proliferation, Invasion, Migration, and EMT by Inhibiting SPRED2-mediated Autophagy in Osteosarcoma Cells

Osteosarcoma is an aggressive malignancy with rapid development and poor prognosis. microRNA-19 (miR-19) plays an important role in several biological processes. Sprouty-related EVH1 domain protein 2 (SPRED2) is a suppressor of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling to inhibit tumor development and progression by promoting autophagy. In this study, we investigated the roles of miR-19, SPRED2, and autophagy in osteosarcoma. We detected the expression of miR-19, SPRED2, epithelial-mesenchymal transition (EMT) markers, and autophagy-related proteins via quantitative real-time polymerase chain reaction or western blot. To evaluate the function of miR-19 and SPRED2, we used MTT and colony formation assays to detect cell proliferation, Transwell, and wound-healing assays to detect cell invasion and migration. Targetscan and luciferase reporter assays confirmed the relationship between SPRED2 and miR-19. The expression of miR-19 was significantly upregulated in osteosarcoma, while SPRED2 was downregulated. miR-19 inhibitor reduced cell proliferation, invasion, migration, and EMT, while its cell biological effects were partially reversed by addition of autophagy inhibitor 3-methyladenine (3-MA) or SPRED2 siRNA in osteosarcoma. SPRED2, a suppressor of ERK/MAPK pathway that is known to trigger autophagy, was identified as a direct target of miR-19. SPRED2 overexpression increased cell proliferation, invasion, migration, and EMT by promoting autophagy, and the effects could be inhibited by 3-MA. Collectively, these findings reveal an underlying mechanism for development of osteosarcoma. miR-19 was upregulated in osteosarcoma cells, and negatively regulated SPRED2, thus promoting the malignant transformation of osteosarcoma cells via inhibiting SPRED2-induced autophagy. Therefore, miR-19/SPRED2 may be a potential target for the treatment of osteosarcoma.

Hyperoxia-induced miR-342-5p down-regulation exacerbates neonatal bronchopulmonary dysplasia via the Raf1 regulator Spred3

BACKGROUND AND PURPOSE

Bronchopulmonary dysplasia (BPD) is the most prevalent chronic paediatric lung disease and is linked to the development of chronic obstructive pulmonary disease. MicroRNA-based regulation of type II alveolar epithelial cell (T2AEC) proliferation and apoptosis is an important factor in the pathogenesis of BPD and warrants further investigation.

EXPERIMENTAL APPROACH

Two murine models of hyperoxic lung injury (with or without miR-342-5p or Sprouty-related, EVH1 domain-containing protein 3 [Spred3] modulation) were employed: a hyperoxia-induced acute lung injury model (100% O₂ on postnatal days 1-7) and the BPD model (100% O₂ on postnatal days 1-4, followed by room air for 10 days). Tracheal aspirate pellets from healthy control and moderate/severe BPD neonates were randomly selected for clinical miR-342-5p analysis.

KEY RESULTS

Hyperoxia decreased miR-342-5p levels in primary T2AECs, MLE12 cells and neonatal mouse lungs. Transgenic miR-342 overexpression in neonatal mice ameliorated survival rates and improved the BPD phenotype and BPD-associated pulmonary arterial hypertension (PAH). T2AEC-specific miR-342 transgenic overexpression, as well as miR-342-5p mimic therapy, also ameliorated the BPD phenotype and associated PAH. miR-342-5p targets the 3'UTR of the Raf1 regulator Spred3, inhibiting Spred3 expression. Treatment with recombinant Spred3 exacerbated the BPD phenotype and associated PAH. Notably, miR-342-5p inhibition under room air conditions did not mimic the BPD phenotype. Moderate/severe BPD tracheal aspirate pellets exhibited decreased miR-342-5p levels relative to healthy control pellets.

CONCLUSION AND IMPLICATIONS

These findings suggest that miR-342-5p mimic therapy may show promise in the treatment or prevention of BPD.

miR-126-3p contributes to sorafenib resistance in hepatocellular carcinoma via downregulating SPRED1

Background

Sorafenib can prolong the survival of patients with advanced hepatocellular carcinoma (HCC). However, drug resistance remains the main obstacle to improving its efficiency. This study aimed to explore the likely molecular mechanism of sorafenib resistance.

Methods

Differentially expressed microRNAs (miRNAs) related to sorafenib response were analyzed with the Limma package in R software. The expression levels of miR-126-3p and sprouty-related EVH1 domain-containing protein 1 (SPRED1) in HCC cells were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell viability and proliferation were detected with Cell Counting Kit-8 (CCK-8), EdU proliferation, and clone formation assays. Transwell assays were performed to measure cell migration and invasion. TargetScan, MicroRNA Target Prediction Database (miRDB), and StarBase v2.0 were used to predict the targets of miR-126-3p. SPRED1 was confirmed as a target gene of miR-126-3p by dual-luciferase reporter assay and Western blotting. Finally, the in vivo anti-tumor effect of LV-miR-126-3p inhibitor combined with sorafenib was evaluated via subcutaneous tumor models.

Results

HCC cells with high expression of miR-126-3p exhibited increased resistance to sorafenib. The results of bioinformatics analysis and the dual-luciferase reporter assay showed that miR-126-3p directly targeted SPRED1. The sensitivity of HCC cells to sorafenib was markedly enhanced by SPRED1 upregulation. Gain- and loss-of function experiments verified that miR-126-3p induced sorafenib resistance in HCC through downregulating SPRED1. Furthermore, the inhibition of miR-126-3p markedly increased the effectiveness of sorafenib against HCC in vivo. Mechanistically, our results suggested that miR-126-3p promoted sorafenib resistance via targeting SPRED1 and activating the ERK signaling pathway.

Conclusions

Our study demonstrates that regulating the miR-126-3p/SPRED1 axis might be a promising strategy for enhancing the antitumor effect of sorafenib in the treatment of HCC.

Identification of key features required for efficient S-acylation and plasma membrane targeting of sprouty-2

Sprouty-2 is an important regulator of growth factor signalling and a tumour suppressor protein. The defining feature of this protein is a cysteine-rich domain (CRD) that contains twenty-six cysteine residues and is modified by S-acylation. In this study, we show that the CRD of sprouty-2 is differentially modified by S-acyltransferase enzymes. The high specificity/low activity zDHHC17 enzyme mediated restricted S-acylation of sprouty-2, and cysteine-265 and -268 were identified as key targets of this enzyme. In contrast, the low specificity/high activity zDHHC3 and zDHHC7 enzymes mediated more expansive modification of the sprouty-2 CRD. Nevertheless, S-acylation by all enzymes enhanced sprouty-2 expression, suggesting that S-acylation stabilises this protein. In addition, we identified two charged residues (aspartate-214 and lysine-223), present on opposite faces of a predicted α-helix in the CRD, which are essential for S-acylation of sprouty-2. Interestingly, mutations that perturbed S-acylation also led to a loss of plasma membrane localisation of sprouty-2 in PC12 cells. This study provides insight into the mechanisms and outcomes of sprouty-2 S-acylation, and highlights distinct patterns of S-acylation mediated by different classes of zDHHC enzymes.

SPRED proteins and their roles in signal transduction, development, and malignancy

The roles of SPRED proteins in signaling, development, and cancer are becoming increasingly recognized. SPRED proteins comprise an N-terminal EVH-1 domain, a central c-Kit-binding domain, and C-terminal SROUTY domain. They negatively regulate signaling from tyrosine kinases to the Ras-MAPK pathway. SPRED1 binds directly to both c-KIT and to the RasGAP, neurofibromin, whose function is completely dependent on this interaction. Loss-of-function mutations in SPRED1 occur in human cancers and cause the developmental disorder, Legius syndrome. Genetic ablation of SPRED genes in mice leads to behavioral problems, dwarfism, and multiple other phenotypes including increased risk of leukemia. In this review, we summarize and discuss biochemical, structural, and biological functions of these proteins including their roles in normal cell growth and differentiation and in human disease.

MicroRNAs as regulators of ERK/MAPK pathway: A comprehensive review

The ERK/MAPK cascade is one the four distinctive MAPK cascades which transmit extracellular signals to intracellular targets. This cascade has an important role in the regulation of several fundamental processes such as proliferation, differentiation and cell response to diverse extrinsic stresses. Moreover, several studies have shown participation of this cascade in the pathogenesis of cancer. Recent investigations have unraveled interaction between microRNAs (miRNAs) and ERK/MAPK cascade. These transcripts reside in both upstream and downstream of this cascade, regulating or being regulated by ERK/MAPK proteins. In the current review, we summarize the role of miRNAs in the regulation of ERK/MAPK and their contribution in the pathogenesis of human disorders with particular focus on cancers.

BRAFV600E drives dedifferentiation in small intestinal and colonic organoids and cooperates with mutant p53 and Apc loss in transformation

BRAF^V600E confers poor prognosis and is associated with a distinct subtype of colorectal cancer (CRC). Little is known, however, about the genetic events driving the initiation and progression of BRAF^V600E mutant CRCs. Recent genetic analyses of CRCs indicate that BRAF^V600E often coexists with alterations in the WNT- and p53 pathways, but their cooperation remains ill-defined. Therefore, we systematically compared small and large intestinal organoids from mice harboring conditional Braf^floxV600E, Trp53^LSL-R172H, and/or Apc^flox/flox alleles. Using these isogenic models, we observe tissue-specific differences toward sudden BRAF^V600E expression, which can be attributed to different ERK-pathway ground states in small and large intestinal crypts. BRAF^V600E alone causes transient proliferation and suppresses epithelial organization, followed by organoid disintegration. Moreover, BRAF^V600E induces a fetal-like dedifferentiation transcriptional program in colonic organoids, which resembles human BRAF^V600E-driven CRC. Co-expression of p53^R172H delays organoid disintegration, confers anchorage-independent growth, and induces invasive properties. Interestingly, p53^R172H cooperates with BRAF^V600E to modulate the abundance of transcripts linked to carcinogenesis, in particular within colonic organoids. Remarkably, WNT-pathway activation by Apc deletion fully protects organoids against BRAF^V600E-induced disintegration and confers growth/niche factor independence. Still, Apc-deficient BRAF^V600E-mutant organoids remain sensitive toward the MEK inhibitor trametinib, albeit p53^R172H confers partial resistance against this clinically relevant compound. In summary, our systematic comparison of the response of small and large intestinal organoids to oncogenic alterations suggests colonic organoids to be better suited to model the human situation. In addition, our work on BRAF-, p53-, and WNT-pathway mutations provides new insights into their cooperation and for the design of targeted therapies.

Progress in experimental research on SPRED protein family

The Sprouty-related Ena/vasodilator-stimulated phosphoprotein homology-1 (EVH-1) domain (SPRED) family of proteins was discovered in 2001. These Sprouty-related tyrosine kinase-binding proteins negatively regulate a variety of growth factor-induced Ras/ERK signaling pathways. In recent years, SPRED proteins have been found to regulate vital activities such as cell development, movement, and proliferation, and to participate in pathophysiological processes such as tumor metastasis, hematopoietic regulation, and allergic reactions. The findings of these studies have important implications regarding the involvement of SPRED proteins in disease. Early studies of SPRED proteins focused mainly on various tumors, cardiovascular diseases, and organ development. However, in recent years, great progress has been made in elucidating the role of SPRED proteins in neuropsychiatric, inflammatory, endocrine, and ophthalmic diseases. This article provides a review of the experimental studies performed in recent years on the SPRED proteins and their role in the pathogenesis of certain diseases.

Influence of Fibroblasts on Mammary Gland Development, Breast Cancer Microenvironment Remodeling, and Cancer Cell Dissemination

The stromal microenvironment regulates mammary gland development and tumorigenesis. In normal mammary glands, the stromal microenvironment encompasses the ducts and contains fibroblasts, the main regulators of branching morphogenesis. Understanding the way fibroblast signaling pathways regulate mammary gland development may offer insights into the mechanisms of breast cancer (BC) biology. In fact, the unregulated mammary fibroblast signaling pathways, associated with alterations in extracellular matrix (ECM) remodeling and branching morphogenesis, drive breast cancer microenvironment (BCM) remodeling and cancer growth. The BCM comprises a very heterogeneous tissue containing non-cancer stromal cells, namely, breast cancer-associated fibroblasts (BCAFs), which represent most of the tumor mass. Moreover, the different components of the BCM highly interact with cancer cells, thereby generating a tightly intertwined network. In particular, BC cells activate recruited normal fibroblasts in BCAFs, which, in turn, promote BCM remodeling and metastasis. Thus, comparing the roles of normal fibroblasts and BCAFs in the physiological and metastatic processes, could provide a deeper understanding of the signaling pathways regulating BC dissemination. Here, we review the latest literature describing the structure of the mammary gland and the BCM and summarize the influence of epithelial-mesenchymal transition (EpMT) and autophagy in BC dissemination. Finally, we discuss the roles of fibroblasts and BCAFs in mammary gland development and BCM remodeling, respectively.

Dominant-negative antagonists of the Ras-ERK pathway: DA-Raf and its related proteins generated by alternative splicing of Raf

The Ras-ERK pathway regulates a variety of cellular and physiological responses, including cell proliferation, differentiation, morphogenesis during animal development, and homeostasis in adults. Deregulated activation of this pathway leads to cellular transformation and tumorigenesis as well as RASopathies. Several negative regulators of this pathway have been documented. Each of these proteins acts at particular points of the pathway, and they exert specific cellular and physiological functions. Among them, DA-Raf1 (DA-Raf), which is a splicing isoform of A-Raf and contains the Ras-binding domain but lacks the kinase domain, antagonizes the Ras-ERK pathway in a dominant-negative manner. DA-Raf induces apoptosis, skeletal myocyte differentiation, lung alveolarization, and fulfills tumor suppressor functions by interfering with the Ras-ERK pathway. After the findings of DA-Raf, several kinase-domain-truncated splicing variants of Raf proteins have also been reported. The family of these truncated proteins represents the concept that alternative splicing can generate antagonistic proteins to their full-length counterparts.

SHP-2 in Lymphocytes' Cytokine and Inhibitory Receptor Signaling

Somewhat counterintuitively, the tyrosine phosphatase SHP-2 (SH2 domain-containing protein tyrosine phosphatase-2) is crucial for the activation of extracellular signal-regulated kinase (ERK) downstream of various growth factor receptors, thereby exerting essential developmental functions. This phosphatase also deploys proto-oncogenic functions and specific inhibitors have recently been developed. With respect to the immune system, the role of SHP-2 in the signaling of cytokines relevant for myelopoiesis and myeloid malignancies has been intensively studied. The function of this phosphatase downstream of cytokines important for lymphocytes is less understood, though multiple lines of evidence suggest its importance. In addition, SHP-2 has been proposed to mediate the suppressive effects of inhibitory receptors (IRs) that sustain a dysfunctional state in anticancer T cells. Molecules involved in IR signaling are of potential pharmaceutical interest as blockade of these inhibitory circuits leads to remarkable clinical benefit. Here, we discuss the dichotomy in the functions ascribed to SHP-2 downstream of cytokine receptors and IRs, with a focus on T and NK lymphocytes. Further, we highlight the importance of broadening our understanding of SHP-2′s relevance in lymphocytes, an essential step to inform on side effects and unanticipated benefits of its therapeutic blockade.

The Sprouty/Spred family as tumor suppressors: Coming of age

The Ras/Raf/ERK pathway is one of the most frequently dysregulated signaling pathways in various cancers. In some such cancers, Ras and Raf are hotspots for mutations, which cause continuous activation of this pathway. However, in some other cancers, it is known that negative regulators of the Ras/Raf/ERK pathway are responsible for uncontrolled activation. The Sprouty/Spred family is broadly recognized as important negative regulators of the Ras/Raf/ERK pathway, and its expression is downregulated in many malignancies, leading to hyperactivation of the Ras/Raf/ERK pathway. After the discovery of this family, intensive research investigated the mechanism by which it suppresses the Ras/Raf/ERK pathway and its roles in developmental and pathophysiological processes. In this review, we discuss the complicated roles of the Sprouty/Spred family in tumor initiation, promotion, and progression and its future therapeutic potential.