ILEI drives epithelial to mesenchymal transition and metastatic progression in the lung cancer cell line A549

PCBP1-mediated regulation of WNT signaling is critical for breast tumorigenesis

Loss of expression or protein kinase B (Akt1)-mediated post-translational modification of the RNA binding protein Poly r(C) binding protein 1 (PCBP1) is closely related to metastatic advancement of breast cancer. However, the role of PCBP1 in tumorigenesis is not completely defined. Using a xenograft orthotopic model of breast tumorigenesis (4T1-Pcbp1-/-), we show here that PCBP1 knockdown-induced tumorigenesis is inhibited by activation of the WNT signaling via treating with the glycogen synthase kinase 3 beta inhibitor TWS119, but not the Akt2/Akt3 inhibitor GSK690693. Mass cytometry-based evaluation of the tumor microenvironment (TME) revealed significantly more regulatory T cells (Tregs) and significantly less cytotoxic T cells in 4T1-Pcbp1-/-mice treated with saline control in comparison to mice treated with TWS119. Infiltrating cytotoxic T cells were phenotypically and functionally exhausted. Treatment with TWS119 resulted in rescue of cytotoxic T cell function and inhibition of suppressor activity of Tregs. Using cytotoxic T cells isolated from healthy donors, we show that TWS119-induced WNT signaling-mediated inhibition of cytotoxic T cell expansion is reliant on expression of PCBP1. In conclusion, decreased PCBP1 expression favors breast tumorigenesis by potentiating skewing of tumor infiltrating T cells towards Tregs, thereby effectively suppressing anti-tumor immunity.

Inducible overexpression of a FAM3C/ILEI transgene has pleiotropic effects with shortened life span, liver fibrosis and anemia in mice

FAM3C/ILEI is an important factor in epithelial-to-mesenchymal transition (EMT) induction, tumor progression and metastasis. Overexpressed in many cancers, elevated ILEI levels and secretion correlate with poor patient survival. Although ILEI's causative role in invasive tumor growth and metastasis has been demonstrated in several cellular tumor models, there are no available transgenic mice to study these effects in the context of a complex organism. Here, we describe the generation and initial characterization of a Tet-ON inducible Fam3c/ILEI transgenic mouse strain. We find that ubiquitous induction of ILEI overexpression (R26-ILEIind) at weaning age leads to a shortened lifespan, reduced body weight and microcytic hypochromic anemia. The anemia was reversible at a young age within a week upon withdrawal of ILEI induction. Vav1-driven overexpression of the ILEIind transgene in all hematopoietic cells (Vav-ILEIind) did not render mice anemic or lower overall fitness, demonstrating that no intrinsic mechanisms of erythroid development were dysregulated by ILEI and that hematopoietic ILEI hyperfunction did not contribute to death. Reduced serum iron levels of R26-ILEIind mice were indicative for a malfunction in iron uptake or homeostasis. Accordingly, the liver, the main organ of iron metabolism, was severely affected in moribund ILEI overexpressing mice: increased alanine transaminase and aspartate aminotransferase levels indicated liver dysfunction, the liver was reduced in size, showed increased apoptosis, reduced cellular iron content, and had a fibrotic phenotype. These data indicate that high ILEI expression in the liver might reduce hepatoprotection and induce liver fibrosis, which leads to liver dysfunction, disturbed iron metabolism and eventually to death. Overall, we show here that the novel Tet-ON inducible Fam3c/ILEI transgenic mouse strain allows tissue specific timely controlled overexpression of ILEI and thus, will serve as a versatile tool to model the effect of elevated ILEI expression in diverse tissue entities and disease conditions, including cancer.

FAM3 family genes are associated with prognostic value of human cancer: a pan-cancer analysis

Family with sequence similarity three member (FAM3) plays a crucial role in the malignant development of various cancers of human. However, there remains doubtful what specific role of FAM3 family genes in pan-cancer. Our study aimed to investigate the role of FAM3 family genes in prognosis, immune subtype, tumor immune microenvironment, stemness score, and anticancer drug sensitivity of pan-cancer. We obtained data from UCSC Xena GDC and CellMiner databases, and used them to study the correlation of the expression, survival, immune subtype, tumor microenvironment, stemness score, and anticancer drug sensitivity between FAM3 family genes with pan-cancer. Furthermore, we investigated the tumor cellular functions and clinical prognostic value FAMC3 in pancreatic cancer (PAAD) using cellular experiments and tissue microarray. Cell Counting Kit-8 (CCK-8), transwell invasion, wound-healing and apoptosis assays were performed to study the effect of FAM3C on SW1990 cells' proliferation, migration, invasion and apoptosis. Immunohistochemical staining was used to study the relationship between FAM3C expression and clinical characteristics of pancreatic cancer patients. The results revealed that FAM3 family genes are significantly differential expression in tumor and adjacent normal tissues in 7 cancers (CHOL, HNSC, KICH, LUAD, LUSC, READ, and STAD). The expression of FAM3 family genes were negatively related with the RNAss, and robust correlated with immune type, tumor immune microenvironment and drug sensitivity. The expression of FAM3 family genes in pan-cancers were significantly different in immune type C1 (wound healing), C2 (IFN-gamma dominant), C3 (inflammatory), C4 (lymphocyte depleted), C5 (immunologically quiet), and C6 (TGF-beta dominant). Meanwhile, overexpression FAM3C promoted SW1990 cells proliferation, migration, invasion and suppressed SW1990 cells apoptosis. While knockdown of FAM3C triggered opposite results. High FAM3C expression was associated with duodenal invasion, differentiation and liver metastasis. In summary, this study provided a new perspective on the potential therapeutic role of FAM3 family genes in pan-cancer. In particular, FAM3C may play an important role in the occurrence and progression of PAAD.

Human FAM3C restores memory-based thermotaxis of Caenorhabditis elegans famp-1/m70.4 loss-of-function mutants

The family with sequence similarity 3 (FAM3) superfamily represents a distinct class of signaling molecules that share a characteristic structural feature. Mammalian FAM3 member C (FAM3C) is abundantly expressed in neuronal cells and released from the synaptic vesicle to the extracellular milieu in an activity-dependent manner. However, the neural function of FAM3C has yet to be fully clarified. We found that the protein sequence of human FAM3C is similar to that of the N-terminal tandem domains of Caenorhabditis elegans FAMP-1 (formerly named M70.4), which has been recognized as a tentative ortholog of mammalian FAM3 members or protein-O-mannose β-1,2-N-acetylglucosaminyltransferase 1 (POMGnT1). Missense mutations in the N-terminal domain, named Fam3L2, caused defects in memory-based thermotaxis but not in chemotaxis behaviors; these defects could be restored by AFD neuron-specific exogenous expression of a polypeptide corresponding to the Fam3L2 domain but not that corresponding to the Fam3L1. Moreover, human FAM3C could also rescue defective thermotaxis behavior in famp-1 mutant worms. An in vitro assay revealed that the Fam3L2 and FAM3C can bind with carbohydrates, similar to the stem domain of POMGnT1. The athermotactic mutations in the Fam3L2 domain caused a partial loss-of-function of FAMP-1, whereas the C-terminal truncation mutations led to more severe neural dysfunction that reduced locomotor activity. Overall, we show that the Fam3L2 domain-dependent function of FAMP-1 in AFD neurons is required for the thermotaxis migration of C. elegans and that human FAM3C can act as a substitute for the Fam3L2 domain in thermotaxis behaviors.

TGFβ-induced expression of long noncoding lincRNA Platr18 controls breast cancer axonogenesis

Tumor axonogenesis is an emerging hallmark of cancer and TGF-beta is a well-known cytokine involved in the control of cancer progression. In this study we identify a novel function for the TGF-beta signaling in cancer aggressivity by promoting cancer axonogenesis.

Metastasis is the leading driver of cancer-related death. Tumor cell plasticity associated with the epithelial–mesenchymal transition (EMT), an embryonic program also observed in carcinomas, has been proposed to explain the colonization of distant organs by the primary tumor cells. Many studies have established correlations between EMT marker expression in the primary tumor and metastasis in vivo. However, the longstanding model of EMT-transitioned cells disseminating to secondary sites is still actively debated and hybrid states are presently considered as more relevant during tumor progression and metastasis. Here, we describe an unexplored role of EMT on the tumor microenvironment by controlling tumor innervation. Using in vitro and in vivo breast tumor progression models, we demonstrate that TGFβ-mediated tumor cell EMT triggers the expression of the embryonic LincRNA Platr18 those elevated expression controls the expression of the axon guidance protein semaphorin-4F and other neuron-related molecules such as IGSF11/VSIG-3. Platr18/Sema4F axis silencing abrogates axonogenesis and attenuates metastasis. Our observations suggest that EMT-transitioned cells are also locally required in the primary tumor to support distant dissemination by promoting axonogenesis, a biological process known for its role in metastatic progression of breast cancer.

Emerging Perspectives on Leukemia Inhibitory Factor and its Receptor in Cancer

Tumorigenesis and metastasis have deep connections to inflammation and inflammatory cytokines, but the mechanisms underlying these relationships are poorly understood. Leukemia Inhibitory Factor (LIF) and its receptor (LIFR), part of the interleukin-6 (IL-6) cytokine family, make up one such ill-defined piece of the puzzle connecting inflammation to cancer. Although other members of the IL-6 family have been shown to be involved in the metastasis of multiple types of cancer, the role of LIF and LIFR has been challenging to determine. Described by others in the past as enigmatic and paradoxical, LIF and LIFR are expressed in a diverse array of cells in the body, and the narrative surrounding them in cancer-related processes has been vague, and at times even contradictory. Despite this, recent insights into their functional roles in cancer have highlighted interesting patterns that may allude to a broader understanding of LIF and LIFR within tumor growth and metastasis. This review will discuss in depth the signaling pathways activated by LIF and LIFR specifically in the context of cancer-the purpose being to summarize recent literature concerning the downstream effects of LIF/LIFR signaling in a variety of cancer-related circumstances in an effort to begin teasing out the intricate web of contradictions that have made this pair so challenging to define.

FAM3C: an emerging biomarker and potential therapeutic target for cancer

FAM3C is a member of the FAM3 family. Recently, overexpression of FAM3C has been reported in numerous types of cancer, including breast and colon cancer. Increasing evidence suggests that elevated FAM3C and its altered subcellular localization are closely associated with tumor formation, invasion, metastasis and poor survival. Moreover, FAM3C has been found to be the regulator of various proteins that associate with cancer, including Ras, STAT3, TGF-β and LIFR. This review summarizes the current knowledge regarding FAM3C, including its structure, expression patterns, regulation, physiological roles and regulatory functions in various malignancies. These findings highlight the importance of FAM3C in cancer development and provide evidence that FAM3C is a novel biomarker and potential therapeutic target for various cancers.

The FAM3C locus that encodes interleukin-like EMT inducer (ILEI) is frequently co-amplified in MET-amplified cancers and contributes to invasiveness

BACKGROUND

Gene amplification of MET, which encodes for the receptor tyrosine kinase c-MET, occurs in a variety of human cancers. High c-MET levels often correlate with poor cancer prognosis. Interleukin-like EMT inducer (ILEI) is also overexpressed in many cancers and is associated with metastasis and poor survival. The gene for ILEI, FAM3C, is located close to MET on chromosome 7q31 in an amplification "hotspot", but it is unclear whether FAMC3 amplification contributes to elevated ILEI expression in cancer. In this study we have investigated FAMC3 copy number gain in different cancers and its potential connection to MET amplifications.

METHODS

FAMC3 and MET copy numbers were investigated in various cancer samples and 200 cancer cell lines. Copy numbers of the two genes were correlated with mRNA levels, with relapse-free survival in lung cancer patient samples as well as with clinicopathological parameters in primary samples from 49 advanced stage colorectal cancer patients. ILEI knock-down and c-MET inhibition effects on proliferation and invasiveness of five cancer cell lines and growth of xenograft tumors in mice were then investigated.

RESULTS

FAMC3 was amplified in strict association with MET amplification in several human cancers and cancer cell lines. Increased FAM3C and MET copy numbers were tightly linked and correlated with increased gene expression and poor survival in human lung cancer and with extramural invasion in colorectal carcinoma. Stable ILEI shRNA knock-down did not influence proliferation or sensitivity towards c-MET-inhibitor induced proliferation arrest in cancer cells, but impaired both c-MET-independent and -dependent cancer cell invasion. c-MET inhibition reduced ILEI secretion, and shRNA mediated ILEI knock-down prevented c-MET-signaling induced elevated expression and secretion of matrix metalloproteinase (MMP)-2 and MMP-9. Combination of ILEI knock-down and c-MET-inhibition significantly reduced the invasive outgrowth of NCI-H441 and NCI-H1993 lung tumor xenografts by inhibiting proliferation, MMP expression and E-cadherin membrane localization.

CONCLUSIONS

These novel findings suggest MET amplifications are often in reality MET-FAM3C co-amplifications with tight functional cooperation. Therefore, the clinical relevance of this frequent cancer amplification hotspot, so far dedicated purely to c-MET function, should be re-evaluated to include ILEI as a target in the therapy of c-MET-amplified human carcinomas.

miRNA‑490‑3p promotes the metastatic progression of invasive ductal carcinoma

MicroRNA (miRNA/mir)‑490‑3p has been defined as a tumor suppressor in different types of cancer, including breast cancer. However, miR‑490‑3p has been shown to function as a tumor suppressor and promoter in a context‑dependent manner in hepatocellular and lung cancer. Contrary to previous studies, the present study revealed that miR‑490‑3p expression was significantly higher in invasive ductal carcinoma (IDC) tissue specimens, the most common form of breast cancer, compared to tumor‑adjacent normal tissue specimens (n=20). Its expression was also higher in the more metastatic breast cancer cell line, MDA‑MB‑231, compared to the non‑metastatic breast cancer cell line, MCF7, and the moderately metastatic breast cancer cell line, MDA‑MB‑468. The expression of miR‑490‑3p was induced following transforming growth factor (TGF)‑β‑induced epithelial‑to‑mesenchymal transition (EMT) in MCF10A cells. Gain‑and loss‑of‑function assays revealed that the expression of miR‑490‑3p regulated the proliferation, colony formation, EMT, migration and invasion in vitro, but not the apoptosis of MDA‑MB‑468 and MDA‑MB‑231 cells. The knockdown of miR‑490‑3p expression in MDA‑MB‑231 cells inhibited experimental metastasis in a tumor xenograft assay. As in lung cancer, miR‑490‑3p was found to target and downregulate the expression of the tumor suppressor RNA binding protein poly r(C) binding protein 1 (PCBP1). PCBP1 protein and miR‑490‑3p expression inversely correlated in patients with ductal carcinoma in situ (DCIS; n=10; no nodal involvement) and IDC (n=10; different stages of metastatic progression) with a significantly higher miR‑490‑3p expression in patients with IDC compared to those with DCIS. The expression of miR‑490‑3p was negatively associated with both overall and disease‑free survival in the patients with breast cancer included in the present study. On the whole, the results confirm a pro‑metastatic role of miR‑490‑3p in IDC, establishing it as a biomarker for disease progression in these patients.

Multiphosphorylation and cellular localization of poly(rC) binding protein 1 during mitosis in hela cell

OBJECTIVE

To monitor the phosphorylation modifications and cellular localization of poly(rC)-binding protein-1 (PCBP1) during the cell cycle progression of Hela cells.

RESULT

Hela cells highly synchronized at five different phases from interphase to mitosis were obtained. Using mitotic phosphoprotein-specific monoclonal antibody MPM-2, the exclusive occurrences of multiphosphorylation statuses of PCBP1 in mitosis were confirmed by a series of spots with increasing acidic pI (isoelectric point) in two rounds of 2D western blotting on the same membrane, and a visible molecular mass shift that can be eliminated by the treatment with λ phosphatase in 1D western blotting. Immnuofluorescence revealed the localization shift of PCBP1 during cell cycle, with accumulations in nucleus as a patch pattern in interphase, and a dispersive distribution without the area of the condensed chromosomes during mitosis.

CONCLUSIONS

These observations of mitosis-specific multiphosphorylations and localization shifts of PCBP1 suggest that the versatile PCBP1 was regulatable in a phosphorylation modification- and temporospatial-dependent manner in mitotic regulatory networks.

Chemoresistance in mesenchymal lung cancer cells is correlated to high regulatory T cell presence in the tumor microenvironment

Most deaths due to lung cancer are a result of metastatic progression. One major problem in treating patients with lung cancer is either the inherent or acquired resistance to chemotherapy. Role of tumor microenvironment in disease progression and resistance to chemotherapy is being increasingly appreciated and reported for various cancers. Hence, the objective of the current study was to define the lung cancer tumor microenvironment. Biopsy tissue specimens and blood samples were collected from stage I-IV lung patients (n = 53). Epithelial and mesenchymal A549 cells were used to test chemosensitivity. CD3+ T cells are the major tumor-infiltrating T lymphocyte subsets in patients with lung cancer, which were independent of disease stage. Functional analysis indicated high expression of the CD4+ helper T cells and low expression of the CD8+ cytotoxic T cells in lung cancer tissue compared to tumor adjacent normal tissue. Within the CD4+ T cell subset, there seems to be significant increase in the regulator T cells (Tregs) which are known to help the tumor in evading the immune system. CDH1 (encoding the epithelial cell marker E-cadherin) and IL2RA (encoding the Treg marker CD25) expression in patients with stage IV lung cancer that were resistant to cisplatin treatment showed an inverse correlation between IL2RA (high) and CDH1 (low) expression. Our results indicate that lung tumor is enriched in Tregs which might potentially explain how lung tumors evade the immune system. © 2019 IUBMB Life, 2019.

FAM3C-YY1 axis is essential for TGFβ-promoted proliferation and migration of human breast cancer MDA-MB-231 cells via the activation of HSF1

Family with sequence similarity three member C (FAM3C) (interleukin‐like EMT inducer [ILEI]), heat shock factor 1 (HSF1) and Ying‐Yang 1 (YY1) have been independently reported to be involved in the pathogenesis of various cancers. However, whether they are coordinated to trigger the development of cancer remains unknown. This study determined the role and mechanism of YY1 and HSF1 in FAM3C‐induced proliferation and migration of breast cancer cells. In human MDA‐MB‐231 breast cancer cell line, transforming growth factor‐β (TGFβ) up‐regulated FAM3C, HSF1 and YY1 expressions. FAM3C overexpression promoted the proliferation and migration of MDA‐MB‐231 cells with YY1 and HSF1 up‐regulation, whereas FAM3C silencing exerted the opposite effects. FAM3C inhibition repressed TGFβ‐induced HSF1 activation, and proliferation and migration of breast cancer cells. YY1 was shown to directly activate HSF1 transcription to promote the proliferation and migration of breast cancer cells. YY1 silencing blunted FAM3C‐ and TGFβ‐triggered activation of HSF1‐Akt‐Cyclin D1 pathway, and proliferation and migration of breast cancer cells. Inhibition of HSF1 blocked TGFβ‐, FAM3C‐ and YY1‐induced proliferation and migration of breast cancer cells. YY1 and HSF1 had little effect on FAM3C expression. Similarly, inhibition of HSF1 also blunted FAM3C‐ and TGFβ‐promoted proliferation and migration of human breast cancer BT‐549 cells. In human breast cancer tissues, FAM3C, YY1 and HSF1 protein expressions were increased. In conclusion, FAM3C activated YY1‐HSF1 signalling axis to promote the proliferation and migration of breast cancer cells. Furthermore, novel FAM3C‐YY1‐HSF1 pathway plays an important role in TGFβ‐triggered proliferation and migration of human breast cancer MDA‐MB‐231 cells.

hnRNP E1 at the crossroads of translational regulation of epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT), in which cells undergo a switch from a polarized, epithelial phenotype to a highly motile fibroblastic or mesenchymal phenotype is fundamental during embryonic development and can be reactivated in a variety of diseases including cancer. Spatio-temporally-regulated mechanisms are constantly orchestrated to allow cells to adapt to their constantly changing environments when disseminating to distant organs. Although numerous transcriptional regulatory factors are currently well-characterized, the post-transcriptional control of EMT requires continued investigation. The hnRNP E1 protein displays a major role in the control of tumor cell plasticity by regulating the translatome through multiple non-redundant mechanisms, and this role is exemplified when E1 is absent. hnRNP E1 binding to RNA molecules leads to direct or indirect translational regulation of specific sets of proteins: (1) hnRNP E1 binding to specific targets has a direct role in translation by preventing elongation of translation; (2) hnRNP E1-dependent alternative splicing can prevent the generation of a competing long non-coding RNA that acts as a decoy for microRNAs (miRNAs) involved in translational inhibition of EMT master regulators; (3) hnRNP E1 binding to the 3’ untranslated region of transcripts can also positively regulate the stability of certain mRNAs to improve their translation. Globally, hnRNP E1 appears to control proteome reprogramming during cell plasticity, either by direct or indirect regulation of protein translation.

MicroRNAs as Potential Targets for Therapeutic Intervention With Metastasis of Non-small Cell Lung Cancer

The death toll of non-small cell lung cancer (NSCLC) patients is primarily due to metastases, which are poorly amenable to therapeutic intervention. In this review we focus on miRs associated with metastasis of NSCLC as potential new targets for anti-metastatic therapy. We discuss miRs validated as therapeutic targets by in vitro data, identification of target(s) and pathway(s) and in vivo efficacy data in at least one clinically-relevant metastasis-related model. A few of the discussed miRs correlate with the clinical status of NSCLC patients. Using miRs as therapeutic agents has the advantage that targeting a single miR can potentially interfere with several metastatic pathways. Depending on their mode of action, the corresponding miRs can be up- or down-regulated compared to normal matching tissues. Here, we describe therapeutic approaches for reconstitution therapy and miR inhibition, general principles of anti-metastatic therapy as well as current technical pitfalls.

Elevated FAM3C promotes cell epithelial- mesenchymal transition and cell migration in gastric cancer

Background

Tumor metastasis is an important factor in treatment failure for advanced gastric cancer. Family with sequence similarity 3 member C (FAM3C) is known to play a critical role in inducing epithelial–mesenchymal transition in several cancer types, while its role in gastric cancer is unidentified. The aim of this study was to investigate the role of FAM3C in gastric cancer and provide new information on the receptor tyrosine-kinase pathway and cytokine-based therapies.

Methods

FAM3C expression was tested in human gastric cancer tissue and adjacent normal mucosa, and the prognostic effect of FAM3C was analyzed in data from the Cancer Genome Atlas (TCGA). The role of FAM3C in gastric cancer proliferation and metastasis was investigated in vitro and in vivo. Western blot analysis and immunofluorescence were used to detect the underlying mechanisms.

Results

FAM3C expression was increased in gastric cancer tissue and showed cytoplasmic distribution. Gastric cancer patients with FAM3C overexpression had significantly worse prognoses based on TCGA data. In the gastric cancer cell lines MKN45 and AGS, knockdown of FAM3C dramatically attenuated cell migration, but had almost no influence on proliferation, while exogenous FAM3C promoted cell migration in a cell line with low FAM3C expression. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of TCGA data showed that FAM3C was mainly associated with genes involved in focal adhesion, extracellular matrix–receptor interactions and the PI3K–Akt signaling pathway. Knockdown of FAM3C in gastric cancer cell lines significantly suppressed epithelial–mesenchymal transition, as demonstrated by increased expression of E-cadherin and decreased expression of Snail and Slug. Furthermore, knockdown of FAM3C strongly suppressed activation of the PI3K–Akt signaling pathway. Finally, we confirmed that FAM3C knockdown significantly decreased metastatic lesions in vivo.

Conclusion

Our study demonstrated that FAM3C can promote gastric cancer metastasis both in vitro and in vivo. FAM3C should be taken into consideration for gastric cancer treatments involving inhibition of the ligands and downstream pathways of receptor tyrosine kinases.

PCBP1 depletion promotes tumorigenesis through attenuation of p27Kip1 mRNA stability and translation

Background

Poly C Binding Protein 1 (PCBP1) is an RNA-binding protein that binds and regulates translational activity of subsets of cellular mRNAs. Depletion of PCBP1 is implicated in various carcinomas, but the underlying mechanism in tumorigenesis remains elusive.

Methods

We performed a transcriptome-wide screen to identify novel bounding mRNA of PCBP1. The bind regions between PCBP1 with target mRNA were investigated by using point mutation and luciferase assay. Cell proliferation, cell cycle, tumorigenesis and cell apoptosis were also evaluated in ovary and colon cancer cell lines. The mechanism that PCBP1 affects p27 was analyzed by mRNA stability and ribosome profiling assays. We analyzed PCBP1 and p27 expression in ovary, colon and renal tumor samples and adjacent non-tumor tissues using RT-PCR, Western Blotting and immunohistochemistry. The prognostic significance of PCBP1 and p27 also analyzed using online databases.

Results

We identified cell cycle inhibitor p27^Kip1 (p27) as a novel PCBP1-bound transcript. We then demonstrated that binding of PCBP1 to p27 3’UTR via its KH1 domain mainly stabilizes p27 mRNA, while enhances its translation to fuel p27 expression, prior to p27 protein degradation. The upregulated p27 consequently inhibits cell proliferation, cell cycle progression and tumorigenesis, whereas promotes cell apoptosis under paclitaxel treatment. Conversely, knockdown of PCBP1 in turn compromises p27 mRNA stability, leading to lower p27 level and tumorigenesis in vivo. Moreover, forced depletion of p27 counteracts the tumor suppressive ability of PCBP1 in the same PCBP1 over-expressing cells. Physiologically, we showed that decreases of both p27 mRNA and its protein expressions are well correlated to PCBP1 depletion in ovary, colon and renal tumor samples, independent of the p27 ubiquitin ligase Skp2 level. Correlation of PCBP1 with p27 is also found in the tamoxifen, doxorubincin and lapatinib resistant breast cancer cells of GEO database.

Conclusion

Our results thereby indicate that loss of PCBP1 expression firstly attenuates p27 expression at post-transcriptional level, and subsequently promotes carcinogenesis. PCBP1 could be used as a diagnostic marker to cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0840-1) contains supplementary material, which is available to authorized users.

Interleukin-like EMT inducer (ILEI) promotes melanoma invasiveness and is transcriptionally up-regulated by upstream stimulatory factor-1 (USF-1)

Interleukin-like EMT inducer (ILEI, FAM3C) is a secreted factor that contributes to the epithelial-to-mesenchymal transition (EMT), a cell-biological process that confers metastatic properties to a tumor cell. However, very little is known about how ILEI is regulated. Here we demonstrate that ILEI is an in vivo regulator of melanoma invasiveness and is transcriptionally up-regulated by the upstream stimulatory factor-1 (USF-1), an E-box-binding, basic-helix-loop-helix family transcription factor. shRNA-mediated knockdown of ILEI in melanoma cell lines attenuated lung colonization but not primary tumor formation. We also identified the mechanism underlying ILEI transcriptional regulation, which was through a direct interaction of USF-1 with the ILEI promoter. Of note, stimulation of endogenous USF-1 by UV-mediated activation increased ILEI expression, whereas shRNA-mediated USF-1 knockdown decreased ILEI gene transcription. Finally, we report that knocking down USF-1 decreases tumor cell migration. In summary, our work reveals that ILEI contributes to melanoma cell invasiveness in vivo without affecting primary tumor growth and is transcriptionally up-regulated by USF-1.

ILEI is an important intermediate participating in the formation of TGF-β1-induced renal tubular EMT

Renal interstitial fibrosis is the most common process by which chronic kidney diseases progress to end-stage renal failure. Epithelial-to-mesenchymal transitions (EMTs) play a crucial role in the progression of renal interstitial fibrosis. A newly identified cytokine, interleukin-like EMT inducer (ILEI), has been linked to EMT in some diseases. However, the effects of ILEI on renal tubular EMT have not yet been well established. Here, we characterize the expression of ILEI in tubular EMT and describe the role and mechanism of ILEI in transforming growth factor beta 1 (TGF-β1)-induced renal tubular EMT. The results indicate that ILEI is involved in renal tubular EMT induced by TGF-β1, as overexpression of ILEI not only induces EMT of HK-2 cells independently but also profoundly enhances EMT in response to TGF-β1. Supporting this finding, ILEI small interfering RNA was found to block the EMT of HK-2 cells induced by TGF-β1. This work additionally suggests ILEI mediates TGF-β1-dependent EMT via the extracellular regulated protein kinases (ERKs) and protein kinase B (Akt) signalling pathways. In conclusion, ILEI appears to play a crucial role in mediating TGF-β1-induced EMT through the Akt and ERK pathways, which may provide a therapeutic target for the treatment of fibrotic kidney diseases.

SIGNIFICANCE OF THE STUDY

There is no study reporting the effect of ILEI in renal EMTs. In this research, we examined the role and mechanism of ILEI in EMT using tubular epithelial cell; we found that ILEI participated in renal tubular EMT, and overexpression of ILEI can not only induce EMT of HK-2 cells independently but also enhance EMT in response to TGF-β1. Meanwhile, we found ILEI small interfering RNA blocked the EMT induced by TGF-β1, and ILEI participates in the EMT caused by TGF-β1 via ERK and Akt signalling pathways. We hoped to provide new ideas in further study on the prevention and treatment of fibrotic kidney diseases.

The interleukin-like epithelial-mesenchymal transition inducer ILEI exhibits a non-interleukin-like fold and is active as a domain-swapped dimer

Production and secretion of pro-metastatic proteins is a feature of many tumor cells. The FAM3C interleukin-like epithelial-to-mesenchymal-transition (EMT) inducer (ILEI) has been shown to be strongly up-regulated in several cancers and to be essential for tumor formation and metastasis in epithelial cells, correlating with a significant decrease in overall survival in colon and breast cancer patients. ILEI has been seen to interact with the γ-secretase presenilin 1 subunit (PS1). However, not much is known about the mechanism-of-action or the detailed ILEI structure. We present here the crystal structures of FAM3C ILEI and show that it exists as monomers but also as covalent dimers. The observed ILEI β-β-α fold confirmed previous indications that the FAM3C proteins do not form classical four-helix-bundle structures as was initially predicted. This provides the first experimental evidence that the interleukin-like EMT inducers are not evolutionarily related to the interleukins. However, more surprisingly, the ILEI dimer structure was found to feature a trans-linked domain swap, converting an intramolecular disulfide to intermolecular. Interestingly, dimeric but not monomeric ILEI was subsequently found to cause a dose-dependent increase in EpRas cell invasiveness comparable with TGF-β, indicating that the dimer might be the active ILEI species. This is in line with a parallel study showing that covalent oligomerization of ILEI is essential for EMT and tumor progression in vivo The structures and the activity data give some first insight into the relationship between dimerization and ILEI function as well as indicate an intriguing link between ILEI, the PS1-protease, TGF-β, and the TGF-β receptor 1.

Interleukin-like EMT inducer regulates partial phenotype switching in MITF-low melanoma cell lines

ILEI (FAM3C) is a secreted factor that contributes to the epithelial-to-mesenchymal transition (EMT), a cell biological process that confers metastatic properties to a tumor cell. Initially, we found that ILEI mRNA is highly expressed in melanoma metastases but not in primary tumors, suggesting that ILEI contributes to the malignant properties of melanoma. While melanoma is not an epithelial cell-derived tumor and does not undergo a traditional EMT, melanoma undergoes a similar process known as phenotype switching in which high (micropthalmia-related transcription factor) MITF expressing (MITF-high) proliferative cells switch to a low expressing (MITF-low) invasive state. We observed that MITF-high proliferative cells express low levels of ILEI (ILEI-low) and MITF-low invasive cells express high levels of ILEI (ILEI-high). We found that inducing phenotype switching towards the MITF-low invasive state increases ILEI mRNA expression, whereas phenotype switching towards the MITF-high proliferative state decreases ILEI mRNA expression. Next, we used in vitro assays to show that knockdown of ILEI attenuates invasive potential but not MITF expression or chemoresistance. Finally, we used gene expression analysis to show that ILEI regulates several genes involved in the MITF-low invasive phenotype including JARID1B, HIF-2α, and BDNF. Gene set enrichment analysis suggested that ILEI-regulated genes are enriched for JUN signaling, a known regulator of the MITF-low invasive phenotype. In conclusion, we demonstrate that phenotype switching regulates ILEI expression, and that ILEI regulates partial phenotype switching in MITF-low melanoma cell lines.

Hepatic Activation of the FAM3C-HSF1-CaM Pathway Attenuates Hyperglycemia of Obese Diabetic Mice

FAM3C is a member of the family with sequence similarity 3 (FAM3) gene family, and this study determined its role and mechanism in regulation of hepatic glucose/lipid metabolism. In obese diabetic mice, FAM3C expression was reduced in the liver, and hepatic FAM3C restoration improved insulin resistance, hyperglycemia, and fatty liver. FAM3C overexpression increased the expression of heat shock factor 1 (HSF1), calmodulin (CaM), and phosphorylated protein kinase B (Akt) and reduced that of gluconeogenic and lipogenic genes in diabetic mouse livers with the suppression of gluconeogenesis and lipid deposition. In cultured hepatocytes, FAM3C overexpression upregulated HSF1 expression, which elevated CaM protein level by inducing CALM1 transcription to activate Akt in a Ca²⁺- and insulin-independent manner. Furthermore, FAM3C overexpression promoted nuclear exclusion of FOXO1 and repressed gluconeogenic gene expression and gluconeogenesis in a CaM-dependent manner in hepatocytes. Hepatic HSF1 overexpression activated the CaM-Akt pathway to repress gluconeogenic and lipogenic gene expression and improve hyperglycemia and fatty liver in obese diabetic mice. In conclusion, the FAM3C-HSF1-CaM-Akt pathway plays important roles in regulating glucose and lipid metabolism in hepatocytes independent of insulin and calcium. Restoring hepatic FAM3C expression is beneficial for the management of type 2 diabetes and fatty liver.

TGFBR2-dependent alterations of exosomal cargo and functions in DNA mismatch repair-deficient HCT116 colorectal cancer cells

BACKGROUND

Colorectal cancers (CRCs) that lack DNA mismatch repair function exhibit the microsatellite unstable (MSI) phenotype and are characterized by the accumulation of frameshift mutations at short repetitive DNA sequences (microsatellites). These tumors recurrently show inactivating frameshift mutations in the tumor suppressor Transforming Growth Factor Beta Receptor Type 2 (TGFBR2) thereby abrogating downstream signaling. How altered TGFBR2 signaling affects exosome-mediated communication between MSI tumor cells and their environment has not been resolved. Here, we report on molecular alterations of exosomes shed by MSI cells and the biological response evoked in recipient cells.

METHODS

Exosomes were isolated and characterized by electron microscopy, nanoparticle tracking, and western blot analysis. TGFBR2-dependent effects on the cargo and functions of exosomes were studied in a MSI CRC model cell line enabling reconstituted and inducible TGFBR2 expression and signaling. Microsatellite frameshift mutations in exosomal and cellular DNA were examined by PCR-based DNA fragment analysis and exosomal protein profiles were identified by mass spectrometry. Uptake of fluorescent-labeled exosomes by hepatoma recipient cells was monitored by confocal microscopy. TGFBR2-dependent exosomal effects on secreted cytokine levels of recipient cells were analyzed by Luminex technology and ELISA.

RESULTS

Frameshift mutation patterns in microsatellite stretches of TGFBR2 and other MSI target genes were found to be reflected in the cargo of MSI CRC-derived exosomes. At the proteome level, reconstituted TGFBR2 expression and signaling uncovered two protein subsets exclusively occurring in exosomes derived from TGFBR2-deficient (14 proteins) or TGFBR2-proficient (five proteins) MSI donor cells. Uptake of these exosomes by recipient cells caused increased secretion (2-6 fold) of specific cytokines (Interleukin-4, Stem Cell Factor, Platelet-derived Growth Factor-B), depending on the TGFBR2 expression status of the tumor cell.

CONCLUSION

Our results indicate that the coding MSI phenotype of DNA mismatch repair-deficient CRC cells is maintained in their exosomal DNA. Moreover, we uncovered that a recurrent MSI tumor driver mutation like TGFBR2 can reprogram the protein content of MSI cell-derived exosomes and in turn modulate the cytokine secretion profile of recipient cells. Apart from its diagnostic potential, these TGFBR2-dependent exosomal molecular and proteomic signatures might help to understand the signaling routes used by MSI tumors. Fricke et al. uncovered coding microsatellite instability-associated mutations of colorectal tumor driver genes like TGFBR2 in MSI tumor cellderived exosomes. Depending on the TGFBR2 expression status of their donor cells, shed exosomes show distinct proteomic signatures and promote altered cytokine secretion profiles in recipient cells.

Mutant HSPB1 causes loss of translational repression by binding to PCBP1, an RNA binding protein with a possible role in neurodegenerative disease

The small heat shock protein HSPB1 (Hsp27) is an ubiquitously expressed molecular chaperone able to regulate various cellular functions like actin dynamics, oxidative stress regulation and anti-apoptosis. So far disease causing mutations in HSPB1 have been associated with neurodegenerative diseases such as distal hereditary motor neuropathy, Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis. Most mutations in HSPB1 target its highly conserved α-crystallin domain, while other mutations affect the C- or N-terminal regions or its promotor. Mutations inside the α-crystallin domain have been shown to enhance the chaperone activity of HSPB1 and increase the binding to client proteins. However, the HSPB1-P182L mutation, located outside and downstream of the α-crystallin domain, behaves differently. This specific HSPB1 mutation results in a severe neuropathy phenotype affecting exclusively the motor neurons of the peripheral nervous system. We identified that the HSPB1-P182L mutant protein has a specifically increased interaction with the RNA binding protein poly(C)binding protein 1 (PCBP1) and results in a reduction of its translational repressive activity. RNA immunoprecipitation followed by RNA sequencing on mouse brain lead to the identification of PCBP1 mRNA targets. These targets contain larger 3′- and 5′-UTRs than average and are enriched in an RNA motif consisting of the CTCCTCCTCCTCC consensus sequence. Interestingly, next to the clear presence of neuronal transcripts among the identified PCBP1 targets we identified known genes associated with hereditary peripheral neuropathies and hereditary spastic paraplegias. We therefore conclude that HSPB1 can mediate translational repression through interaction with an RNA binding protein further supporting its role in neurodegenerative disease.

MicroRNA-490 regulates lung cancer metastasis by targeting poly r(C)-binding protein 1

Lung cancer remains a leading cause of cancer-related mortality, with metastatic progression remaining the single largest cause of lung cancer mortality. Hence, it is imperative to determine reliable biomarkers of lung cancer prognosis. MicroRNA-490-3p has been previously reported to be a positive prognostic biomarker for hepatocellular cancer. However, its role in human lung cancer has not yet been elucidated. Here, we report that hsa-miR-490-3p expression is significantly higher in human lung cancer tissue specimens and cell line. Gain- and loss-of-function studies of hsa-miR-490-3p showed that it regulates cell proliferation and is required for induction of in vitro migration and invasion-the latter being a hallmark of epithelial to mesenchymal transition. In situ analysis revealed that hsa-miR-490-3p targets poly r(C)-binding protein 1 (PCBP1), which has been previously shown to be a negative regulator of lung cancer metastasis. Reporter assays confirmed PCBP1 as a bona fide target of miR-490-3p, and metagenomic analysis revealed an inverse relation between expression of miR-490-3p and PCBP1 in metastatic lung cancer patients. In fact, PCBP1 expression, as detected by immunohistochemistry, was undetectable in advanced stages of lung cancer patients' brain and lymph node tissues. Xenograft tail vein colonization assays proved that high expression of miR-490-3p is a prerequisite for metastatic progression of lung cancer. Our results suggest that hsa-miR-490-3p might be a potential biomarker for lung cancer prognosis. In addition, we can also conclude that the lung cancer cells have evolved refractory mechanisms to downregulate the expression of the metastatic inhibitor, PCBP1.

Neuronal expression of ILEI/FAM3C and its reduction in Alzheimer's disease

Decrease in brain amyloid-β (Aβ) accumulation is a leading strategy for treating Alzheimer's disease (AD). However, the intrinsic mechanism of the regulation of brain Aβ production is largely unknown. Previously, we reported that ILEI (also referred to as FAM3C) binds to the γ-secretase complex and suppresses Aβ production without inhibiting γ-secretase activity. In this study, we examined ILEI expression in mouse brain using immunohistochemistry and subcellular fractionation. Brain ILEI showed widespread expression in neurons and ependymal cells but not in glial and vascular endothelial cells. Neuronal ILEI resided in perinuclear vesicular structures, which were positive for a marker protein of the trans-Golgi network. Although ILEI immunostaining was negative at synaptic terminals, synaptosome fractionation analysis suggested that ILEI was enriched in presynaptic terminals, particularly in the active zone-docked synaptic vesicles. ILEI expression levels in brain peaked during the postnatal period and declined with age. In comparison with age-matched control brains, the number of ILEI-immunoreactive neurons decreased in AD brains, although the subcellular localization was unaltered. Our results suggest that a decline of ILEI expression may cause accumulation of Aβ in the brain and the eventual development of AD.

αCP binding to a cytosine-rich subset of polypyrimidine tracts drives a novel pathway of cassette exon splicing in the mammalian transcriptome

Alternative splicing (AS) is a robust generator of mammalian transcriptome complexity. Splice site specification is controlled by interactions of cis-acting determinants on a transcript with specific RNA binding proteins. These interactions are frequently localized to the intronic U-rich polypyrimidine tracts (PPT) located 5′ to the majority of splice acceptor junctions. αCPs (also referred to as polyC-binding proteins (PCBPs) and hnRNPEs) comprise a subset of KH-domain proteins with high affinity and specificity for C-rich polypyrimidine motifs. Here, we demonstrate that αCPs promote the splicing of a defined subset of cassette exons via binding to a C-rich subset of polypyrimidine tracts located 5′ to the αCP-enhanced exonic segments. This enhancement of splice acceptor activity is linked to interactions of αCPs with the U2 snRNP complex and may be mediated by cooperative interactions with the canonical polypyrimidine tract binding protein, U2AF65. Analysis of αCP-targeted exons predicts a substantial impact on fundamental cell functions. These findings lead us to conclude that the αCPs play a direct and global role in modulating the splicing activity and inclusion of an array of cassette exons, thus driving a novel pathway of splice site regulation within the mammalian transcriptome.

Prognostic significance of FAM3C in esophageal squamous cell carcinoma

Background

Family with sequence similarity 3, member C (FAM3C) has been identified as a novel regulator in epithelial-mesenchymal transition (EMT) and metastatic progression. However, the role of FAM3C in esophageal squamous cell carcinoma (ESCC) remains unexplored. The purpose of present study is to illustrate the role of FAM3C in predicting outcomes of patients with ESCC.

Methods

FAM3C expression was measured in ESCC tissues and the matched adjacent nontumorous tissues by quantitative real-time RT-PCR and Western blot analysis. The relationship between FAM3C expression and prognosis of ESCC patients was further evaluated by univariate and multivariate regression analyses. Univariate and multivariate analyses of the prognostic factors were performed using Cox proportional hazards model.

Results

The FAM3C mRNA expression was remarkably upregulated in ESCC compared with their nontumor counterparts (P < 0.001). In addition, high expression of FAM3C was significantly associated with pT stage (P = 0.014) , pN stage (P = 0.026) and TNM stage (P = 0.003). Kaplan-Meier analysis showed that the 7-year overall survival rate in the group with high expression of FAM3C was poorer than that in low expression group (32.0 versus 70.9 %; P < 0.001). Univariate and multivariate analyses demonstrated that FAM3C was an independent risk factor for overall survival. Moreover, Stratified analysis revealed that FAM3C expression could differentiate the prognosis of patients in early clinical stage (TNM stage I-II).

Conclusions

FAM3C expression was dramatically increased in ESCC and might serve as a valuable prognostic indicator for ESCC patients after surgery.

Enhanced glucose tolerance in pancreatic-derived factor (PANDER) knockout C57BL/6 mice

Pancreatic-derived factor (PANDER; also known as FAM3B) is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas. PANDER has been hypothesized to regulate fasting and fed glucose homeostasis, hepatic lipogenesis and insulin signaling, and to serve a potential role in the onset or progression of type 2 diabetes (T2D). Despite having potentially pivotal pleiotropic roles in glycemic regulation and T2D, there has been limited generation of stable animal models for the investigation of PANDER function, and there are no models on well-established genetic murine backgrounds for T2D. Our aim was to generate an enhanced murine model to further elucidate the biological function of PANDER. Therefore, a pure-bred PANDER knockout C57BL/6 (PANKO-C57) model was created and phenotypically characterized with respect to glycemic regulation and hepatic insulin signaling. The PANKO-C57 model exhibited an enhanced metabolic phenotype, particularly with regard to enhanced glucose tolerance. Male PANKO-C57 mice displayed decreased fasting plasma insulin and C-peptide levels, whereas leptin levels were increased as compared with matched C57BL/6J wild-type mice. Despite similar peripheral insulin sensitivity between both groups, hepatic insulin signaling was significantly increased during fasting conditions, as demonstrated by increased phosphorylation of hepatic PKB/Akt and AMPK, along with mature SREBP-1 expression. Insulin stimulation of PANKO-C57 mice resulted in increased hepatic triglyceride and glycogen content as compared with wild-type C57BL/6 mice. In summary, the PANKO-C57 mouse represents a suitable model for the investigation of PANDER in multiple metabolic states and provides an additional tool to elucidate the biological function and potential role in T2D.

PCBP1 is an important mediator of TGF-β-induced epithelial to mesenchymal transition in gall bladder cancer cell line GBC-SD

Gall bladder carcinoma (GBC) is the seventh most common cancer across the globe and the most common malignancy of the biliary tract. Most GBC related deaths occur due to secondary progression and metastasis to distant organs. Epithelial-mesenchymal transition (EMT) is an important pre-requisite for tumor metastasis, however its mechanism in GBC has not yet been defined. Using the GBC-SD cell line, we have uncovered an important mediator, poly r(C) binding protein-1 (PCBP1), of transforming growth factor-beta (TGF-β)-induced EMT in GBC. Our results show that TGF-β treatment resulted in PCBP1 phosphorylation in accordance with similar observation in other model systems. We further showed through gain- and loss-of-function assays that PCBP1 expression levels regulate the capacity of GBC-SD cells to migrate and invade in vitro. Finally, our results showed that PCBP1 expression levels also regulate generation of CD44(+)CD24(-) progenitor cell population in GBC-SD cells after TGF-β treatment. Cumulatively, our results indicate, pending further validation, that PCBP1 might be a prognostic marker for GBC metastasis.