AF10-dependent transcription is enhanced by its interaction with FLRG

FSTL3 promotes tumor immune evasion and attenuates response to anti-PD1 therapy by stabilizing c-Myc in colorectal cancer

Programmed cell death 1 ligand 1 (PDL1)/programmed cell death 1 (PD1) blockade immunotherapy provides a prospective strategy for the treatment of colorectal cancer (CRC), but various constraints on the effectiveness of the treatment are still remaining. As reported in previous studies, follistatin-like 3 (FSTL3) could mediate inflammatory response in macrophages by induction lipid accumulation. Herein, we revealed that FSTL3 were overexpressed in malignant cells in the CRC microenvironment, notably, the expression level of FSTL3 was related to tumor immune evasion and the clinical efficacy of anti-PD1 therapy. Further studies determined that hypoxic tumor microenvironment induced the FSTL3 expression via HIF1α in CRC cells, FSTL3 could bind to the transcription factor c-Myc (354-406 amino acids) to suppress the latter's ubiquitination and increase its stability, thereby to up-regulated the expression of PDL1 and indoleamine 2,3-dioxygenase 1 (IDO1). The results in the immunocompetent tumor models verified that FSLT3 knockout in tumor cells increased the proportion of CD8+ T cells in the tumor microenvironment, reduced the proportion of regulatory T cells (CD25+ Foxp3+) and exhausted T cells (PD1+ CD8+), and synergistically improved the anti-PD1 therapy efficacy. To sum up, FSTL3 enhanced c-Myc-mediated transcriptional regulation to promote immune evasion and attenuates response to anti-PD1 therapy in CRC, suggesting the potential of FSTL3 as a biomarker of immunotherapeutic efficacy as well as a novel immunotherapeutic target in CRC.

The cytoplasmic expression of FSTL3 correlates with colorectal cancer progression, metastasis status and prognosis

Follistatin-like (FSTL) family members are associated with cancer progression. However, differences between FSTL members with identical cancer types have not been systematically investigated. Among the most malignant tumours worldwide, colorectal cancer (CRC) has high metastatic potential and chemoresistance, which makes it challenging to treat. A systematic examination of the relationship between the expression of FSTL family members in CRC will provide valuable information for prognosis and therapeutic development. Based on large cohort survival analyses, we determined that FSTL3 was associated with a significantly worse prognosis in CRC at the RNA and protein levels. Immunohistochemistry staining of CRC specimens revealed that FSTL3 expression levels in the cytosol were significantly associated with a poor prognosis in terms of overall and disease-free survival. Molecular simulation analysis showed that FSTL3 participated in multiple cell motility signalling pathways via the TGF-β1/TWIST1 axis to control CRC metastasis. The findings provide evidence of the significance of FSTL3 in the oncogenesis and metastasis of CRC. FSTL3 may be useful as a diagnostic or prognostic biomarker, and as a potential therapeutic target.

MLLT10 in benign and malignant hematopoiesis

Non-random chromosomal translocations involving the putative transcription factor Mixed Lineage Leukemia Translocated to 10 (MLLT10, also known as AF10) are commonly observed in both acute myeloid and lymphoid leukemias and are indicative of a poor prognosis. Despite the well-described actions of oncogenic MLLT10 fusion proteins, the role of wild-type MLLT10 in hematopoiesis is not well characterized. The protein structure and several interacting partners have been described and provide indications as to the potential functions of MLLT10. This review examines these aspects of MLLT10, contextualizing its function in benign and malignant hematopoiesis.

Keeping RNA polymerase II on the run: Functions of MLL fusion partners in transcriptional regulation

Since the identification of key MLL fusion partners as transcription elongation factors regulating expression of HOX cluster genes during hematopoiesis, extensive work from the last decade has resulted in significant progress in our overall mechanistic understanding of role of MLL fusion partner proteins in transcriptional regulation of diverse set of genes beyond just the HOX cluster. In this review, we are going to detail overall understanding of role of MLL fusion partner proteins in transcriptional regulation and thus provide mechanistic insights into possible MLL fusion protein-mediated transcriptional misregulation leading to aberrant hematopoiesis and leukemogenesis.

Follistatin-like 3, an activin A binding protein, is involved in early pregnancy loss

BACKGROUND

Early pregnancy loss (EPL), a common and severe complication in pregnancy, has a long-term personal and social impact. It was previously reported that follistatin-like 3(FSTL3), an activin A binding protein, contributes to the invasion and migration of trophoblast. Simultaneously, activin A induces the release of FSTL3 and the elevated activin A is found to be associated with pregnancy loss in women. This study aimed to identify the roles of FSTL3 in the establishment and maintenance of pregnancy, and to determine whether FSTL3 is involved in the pathophysiology of EPL.

METHODS

Endometrial Ishikawa cells and JAR cells were cultured and FSTL3 siRNA was used to silence FSTL3. The trophoblast spheroids mimicking embryos were used in an embryonic adhesion system. The system aimed to investigate the role of FSTL3 silence on embryonic adhesion onto endometrial cell in vitro. The ICR mice model in vivo was used to investigate whether the FSTL3 works in embryonic implantation. The western blotting was used to determine the expression of FSTL3 and activin A.

RESULTS

In the in vitro study, silence of FSTL3 in JAR cells significantly reduced the number of trophoblast spheroids adhered onto Ishikawa cells compared with the scramble siRNA. For the in vivo study, the number of embryos implanted in the uterine horn injected with FATL3 siRNA mixture was significantly less than that in control group. In the case control study, both the expression of FSTL3 and activin A in EPL women were significantly higher than that in controls.

CONCLUSIONS

FSTL3 plays a biological role in the establishment and maintenance of normal pregnancy. Moreover, FSTL3 may be involved in the early pregnancy loss via neutralizing the elevated activin A.

MLLT10 promotes tumor migration, invasion, and metastasis in human colorectal cancer

OBJECTIVES

Colorectal cancer (CRC), one of the most aggressive gastrointestinal malignancies, is a frequently diagnosed life-threatening cancer worldwide. Most CRC patients have poor prognosis mainly because of frequent metastasis and recurrence. Thus, it is crucial to find out some new biomarkers and to show deeper insights into the mechanisms of CRC. MLLT10, Myeloid/lymphoid or mixed-lineage leukemia translocated to 10, also known as AF10, a recurrent MLL partner. In this study, we found that MLLT10 promotes CRC tumor invasion and metastasis both in vitro and in vivo.

METHODS

Here, the expression of MLLT10 was evaluated by immunohistochemistry. Then, the plasmid and lentivirus particles for MLLT10 overexpression or knockdown were designed and constructed into SW620 and HT29 cells. Finally, cell proliferation assay, cell adhesion assay, transwell migration, and invasion assay were used to detect the migration and invasion ability of MLLT10 in CRC cells. A tail vein injection assay was employed to evaluate the role of MLLT10 in tumor metastases.

RESULTS

MLLT10 expression was significantly higher in CRC tissues than in noncancerous tissues and was associated with some clinicopathological factors. In vitro, the overexpression of MLLT10 promoted CRC cell migration and invasion, while after MLLT10 was knocked down, the opposite results were observed. Furthermore, we used animal metastasis models to detect the function of MLLT10 in vivo, the results are same with the outcomes in vitro. In lung metastasis sites, the knockdown of MLLT10 in SW620 cells significantly inhibited Vimentin expression, whereas the E-Cadherin was increased.

CONCLUSIONS

These results indicate that MLLT10 regulates the metastasis of CRC cells via EMT.

Uteroglobin and FLRG concentrations in aqueous humor are associated with age in primary open angle glaucoma patients

Background

The pathophysiological changes occurring in the trabecular meshwork in primary open angle glaucoma are poorly understood, but are thought to include increased extracellular matrix deposition, trabecular meshwork cell apoptosis, inflammation, trabecular meshwork calcification and altered protein composition of the aqueous humor. Although many proteins are present in aqueous humor, relatively few have been studied extensively, and their potential roles in primary open angle glaucoma are unknown.

Methods

Analyte concentrations in aqueous humor from 19 primary open angle glaucoma and 18 cataract patients were measured using a multiplex immunoassay. Fisher’s exact test was used to assess statistical significance between groups, and correlations of analyte concentrations with age, intraocular pressure, pattern standard deviation, mean deviation, cup-to-disc ratio and disease duration since commencing treatment were tested by Spearman’s method.

Results

CHI3L1, FLRG, HGF, MIF, P-selectin and Uteroglobin were detected in more than 50% of samples of one or both patient groups, some of which have not previously been quantified in aqueous humor. In the glaucoma but not the cataract group, significant correlations were determined with age for Uteroglobin/SCGB1A1 (r_s = 0.805, p < 0.0001) and FLRG (r_s = 0.706, p = 0.0007). Furthermore, HGF correlated significantly with disease duration (r_s = − 0.723, p = 0.0007). There were no differences in analyte concentrations between groups, and no other significant associations with clinical descriptors that passed correction for multiple testing.

Conclusions

The correlations of uteroglobin and FLRG with age in primary open angle glaucoma but not cataract may suggest a heightened requirement for anti-inflammatory (uteroglobin) or anti-calcification (FLRG) activity in the ageing glaucomatous trabecular meshwork.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0723-4) contains supplementary material, which is available to authorized users.

The conserved PHD1-PHD2 domain of ZFP-1/AF10 is a discrete functional module essential for viability in Caenorhabditis elegans

Plant homeodomain (PHD)-type zinc fingers play an important role in recognizing chromatin modifications and recruiting regulatory proteins to specific genes. A specific module containing a conventional PHD finger followed by an extended PHD finger exists in the mammalian AF10 protein, among a few others. AF10 has mostly been studied in the context of the leukemic MLL-AF10 fusion protein, which lacks the N-terminal PHD fingers of AF10. Although this domain of AF10 is the most conserved region of the protein, its biological significance has not been elucidated. In this study, we used genetic and biochemical approaches to examine the PHD1-PHD2 region of the Caenorhabditis elegans ortholog of AF10, zinc finger protein 1 (ZFP-1). We demonstrate that the PHD1-PHD2 region is essential for viability and that the first PHD finger contributes to the preferred binding of PHD1-PHD2 to lysine 4-methylated histone H3 tails. Moreover, we show that ZFP-1 localization peaks overlap with H3K4 methylation-enriched promoters of actively expressed genes genomewide and that H3K4 methylation is important for ZFP-1 localization to promoters in the embryo. We predict that the essential biological role of the PHD1-PHD2 module of ZFP-1/AF10 is connected to the regulation of actively expressed genes during early development.

AF10 plays a key role in the survival of uncommitted hematopoietic cells

Hematopoiesis is a complex process regulated by both cell intrinsic and cell extrinsic factors. Alterations in the expression of critical genes during hematopoiesis can modify the balance between stem cell differentiation and proliferation, and may ultimately give rise to leukemia and other diseases. AF10 is a transcription factor that has been implicated in the development of leukemia following chromosomal rearrangements between the AF10 gene and one of at least two other genes, MLL and CALM. The link between AF10 and leukemia, together with the known interactions between AF10 and hematopoietic regulators, suggests that AF10 may be important in hematopoiesis and in leukemic transformation. Here we show that AF10 is important for proper hematopoietic differentiation. The induction of hematopoietic differentiation in both human hematopoietic cell lines and murine total bone marrow cells triggers a decrease of AF10 mRNA and protein levels, particularly in stem cells and multipotent progenitors. Gain- and loss-of-function studies demonstrate that over- or under-expression of AF10 leads to apoptotic cell death in stem cells and multipotent progenitors. We conclude that AF10 plays a key role in the maintenance of multipotent hematopoietic cells.

The clathrin-binding domain of CALM-AF10 alters the phenotype of myeloid neoplasms in mice

The PICALM (CALM) gene, whose product is involved in clathrin-mediated endocytosis, has been identified in two recurring chromosomal translocations, involving either MLL or MLLT10 (AF10). We developed a mouse model of CALM-AF10⁺ leukemia to examine the hypothesis that disruption of endocytosis contributes to leukemogenesis. Exclusion of the C-terminal portion of CALM from the fusion protein, which is required for optimal binding to clathrin, resulted in the development of a myeloproliferative disease, while inclusion of this domain led to the development of acute myeloid leukemia and changes in gene expression of several cancer-related genes, notably Pim1 and Crebbp. Nonetheless, the development of leukemia could not be attributed directly to interference with endocytosis or consequential changes in proliferation and signaling. In leukemia cells, full-length CALM-AF10 localized to the nucleus with no consistent effect on growth factor endocyctosis, and suppressed H3K79 methylation regardless of the presence of clathrin. Using FRET analysis, we show that CALM-AF10 has a propensity to homo-oligomerize, raising the possibility that the function of endocytic proteins involved in chimeric fusions may be to provide dimerization properties, a recognized mechanism for unleashing oncogenic properties of chimeric transcription factors, rather than disrupting the internalization of growth factor receptors.

The CALM and CALM/AF10 interactor CATS is a marker for proliferation

The CATS protein was recently identified as a novel CALM interacting protein. CATS increases the nuclear and specifically the nucleolar localization of the leukemogenic CALM/AF10 fusion protein. We cloned and characterized the murine Cats gene. Detailed analysis of murine Cats expression during mouse embryogenesis showed an association with rapidly proliferating tissues. Interestingly, the Cats transcript is highly expressed in murine hematopoietic cells transformed by CALM/AF10. The CATS protein is highly expressed in leukemia, lymphoma and tumor cell lines but not in non-proliferating T-cells or human peripheral blood lymphocytes. CATS protein levels are cell cycle dependent and it is induced by mitogens, suggesting a role of CATS in the control of cell proliferation and possibly CALM/AF10-mediated leukemogenesis.