Emerging therapeutic strategies for metastatic uveal melanoma: Targeting driver mutations.

Uveal melanoma (UM) is the most common primary malignant intraocular tumor in adults. Although primary UM can be effectively controlled, a significant proportion of cases (40% or more) eventually develop distant metastases, commonly in the liver. Metastatic UM remains a lethal disease with limited treatment options. The initiation of UM is typically attributed to activating mutations in GNAQ or GNA11. The elucidation of the downstream pathways such as PKC/MAPK, PI3K/AKT/mTOR, and Hippo-YAP have provided potential therapeutic targets. Concurrent mutations in BRCA1 associated protein 1 (BAP1) or splicing factor 3b subunit 1 (SF3B1) are considered crucial for the acquisition of malignant potential. Furthermore, in preclinical studies, actionable targets associated with BAP1 loss or oncogenic mutant SF3B1 have been identified, offering promising avenues for UM treatment. This review aims to summarize the emerging targeted and epigenetic therapeutic strategies for metastatic UM carrying specific driver mutations and the potential of combining these approaches with immunotherapy, with particular focus on those in upcoming or ongoing clinical trials.

1,3-Substituted ß-Carboline Derivatives as Potent Chemotherapy for the Treatment of Cystic Echinococcosis.

Echinococcosis is a global public health issue that generally occurs in areas with developed animal husbandry. In search of safe and effective therapeutic agents against echinococcosis, we designed and synthesized new 1,3-substituted ß-carboline derivatives based on harmine. Among them, compounds 1a, 1c, and 1e displayed potent inhibitory activity against Echinococcus granulosus in vitro, significantly better than albendazole and harmine. The morphological detection revealed that 1a, 1c, and 1e significantly changed the ultrastructure of Echinococcus granulosus protoscolices (PSCs). Furthermore, pharmacokinetic studies suggested that 1a possessed a better metabolic property. Encouragingly, 1a exhibited a highest cyst inhibition rate as 76.8% in vivo and did not display neurotoxicity in mice. Further mechanistic research illustrated that 1a has the potential to induce autophagy in PSCs, which may be responsible for the therapeutic effect of the drugs. Together, 1a could be a promising therapeutic agent against echinococcosis, warranting further study.

[The Role and Significance of Hepatic Environmental Cells in Tumor Metastatic Colonization to Liver].

Metastasis, a main cause of death in tumor patients, is a complicated process that involves multiple steps, presenting a major clinical challenge. Tumor cells break the physical boundaries of a primary tumor, intravasate into the lumina of blood vessels, travel around through blood circulation, extravasate into distant organs, colonize the host organs, and eventually develop into the foci of metastatic cancer. The metastasis of tumor cells exhibits organ-tropism, i.e., tumor cells preferentially spread to specific organs. Liver is a common site for metastasis. The pattern of metastasis in uveal melanoma, colorectal carcinoma, and pancreatic ductal adenocarcinoma shows organ-tropism for liver. The anatomical structure of liver determines its hemodynamic characteristics, e.g., low pressure and slow blood flow, which tend to facilitate the stasis and colonization of tumor cells in the liver. Besides the hemodynamic features, the metastatic colonization of liver depends largely on the interaction between tumor cells and the hepatic microenvironment (especially liver-resident cellular components). Resident cells of the hepatic microenvironment include hepatocytes, liver sinusoidal endothelial cells (LSECs), hepatic stellate cells (HSCs), Kupffer cells (KCs), etc. Herein, we discussed the role and significance of liver-resident cells in the metastatic colonization of tumor in the liver.

Ferroptosis induced by DCPS depletion diminishes hepatic metastasis in uveal melanoma.

Hepatic metastasis develops in ∼50% of uveal melanoma (UM) patients with scarcely effective treatment resulting in lethality. The underlying mechanism of liver metastasis remains elusive. Ferroptosis, a cell death form characterized by lipid peroxide, in cancer cells may decrease metastatic colonization. In the present study, we hypothesized that decapping scavenger enzymes (DCPS) impact ferroptosis by regulating mRNA decay during the metastatic colonization of UM cells to liver. We found that inhibition of DCPS by shRNA or RG3039 induced gene transcript alteration and ferroptosis through reducing the mRNA turnover of GLRX. Ferroptosis induced by DCPS inhibition eliminates cancer stem-like cells in UM. Inhibition of DCPS hampered the growth and proliferation both in vitro and in vivo. Furthermore, targeting DCPS diminished hepatic metastasis of UM cells. These findings may shed light on the understanding of DCPS-mediated pre-mRNA metabolic pathway in UM by which disseminated cells gain enhanced malignant features to promote hepatic metastasis, providing a rational target for metastatic colonization in UM.

Protocol for isolation and analysis of the leukemia stem cells in BCR-ABL-driven chronic myelogenous leukemia mice.

Practical procedures for sorting and analysis of leukemia stem cells (LSCs) are to improve our understanding of chronic myelogenous leukemia (CML). Here, we present a detailed magnetic-bead-based sorting and flow-cytometry-based analysis protocol for LSCs in BCR-ABL-driven CML mice. We describe steps for sorting and functional analysis of BCR-ABL-expressing c-Kit+ cells (GFP+c-Kit+) from CML mice as well as antibody staining and gating strategies for characterization of leukemia stem/progenitor cells and myeloid leukemia cells. For complete details on the use and execution of this protocol, please refer to Liu et al. (2022).1.

Reciprocal positive regulation between BRD4 and YAP in GNAQ-mutant uveal melanoma cells confers sensitivity to BET inhibitors.

Uveal melanoma (UM) is the most common intraocular cancer in adults. UMs are usually initiated by a mutation in GNAQ or GNA11 (encoding Gq or G11, respectively), unlike cutaneous melanomas (CMs), which usually carry a BRAF or NRAS mutation. Currently, there are no clinically effective targeted therapies for UM carrying Gq/11 mutations. Here, we identified a causal link between Gq activating mutations and hypersensitivity to bromodomain and extra-terminal (BET) inhibitors. BET inhibitors transcriptionally repress YAP via BRD4 regardless of Gq mutation status, independently of Hippo core components LATS1/2. In contrast, YAP/TAZ downregulation reduces BRD4 transcription exclusively in Gq-mutant cells and LATS1/2 double knockout cells, both of which are featured by constitutively active YAP/TAZ. The transcriptional interdependency between BRD4 and YAP identified in Gq-mutated cells is responsible for the preferential inhibitory effect of BET inhibitors on the growth and dissemination of Gq-mutated UM cells compared to BRAF-mutated CM cells in both culture cells and animal models. Our findings suggest BRD4 as a viable therapeutic target for Gq-driven UMs that are addicted to unrestrained YAP function.

Downregulation of HINFP induces senescence-associated secretory phenotype to promote metastasis in a non-cell-autonomous manner in bladder cancer.

Transcription dysregulation is a salient characteristic of bladder cancer (BC), but no appropriate therapeutic target for it has been established. Here, we found that heterogeneous downregulation of histone H4 transcription factor (HINFP) was associated with senescence in BC tissues and that lower HINFP expression could predict an unfavorable outcome in BC patients. Knockout of HINFP transcriptionally inhibited H1F0 and H1FX to trigger DNA damage, consequently inducing cell senescence to repress the proliferation and growth of BC cells. However, the senescence-associated secretory phenotype, characterized by increases in MMP1/3, enhances the invasion and metastasis of non-senescent BC cells. Histone deacetylase inhibitors (HDACis) could efficiently eliminate the senescent cells induced by HINFP knockout to suppress the invasion and metastasis of BC cells. Our study suggests that HDACis, widely used in multiple cancer types in a clinical context, may also benefit BC patients with metastases induced by cell senescence.

Loss of PRMT7 reprograms glycine metabolism to selectively eradicate leukemia stem cells in CML.

Our group has reported previously on the role of various members of the protein arginine methyltransferase (PRMT) family, which are involved in epigenetic regulation, in the progression of leukemia. Here, we explored the role of PRMT7, given its unique function within the PRMT family, in the maintenance of leukemia stem cells (LSCs) in chronic myeloid leukemia (CML). Genetic loss of Prmt7, and the development and testing of a small-molecule specific inhibitor of PRMT7, showed that targeting PRMT7 delayed leukemia development and impaired self-renewal of LSCs in a CML mouse model and in primary CML CD34+ cells from humans without affecting normal hematopoiesis. Mechanistically, loss of PRMT7 resulted in reduced expressions of glycine decarboxylase, leading to the reprograming of glycine metabolism to generate methylglyoxal, which is detrimental to LSCs. These findings link histone arginine methylation with glycine metabolism, while suggesting PRMT7 as a potential therapeutic target for the eradication of LSCs in CML.

Super-enhancer landscape reveals leukemia stem cell reliance on X-box binding protein 1 as a therapeutic vulnerability.

Relapse of patients with chronic myelogenous leukemia (CML) may occur at least partially because leukemia stem cells (LSCs) lack sensitivity to tyrosine kinase inhibitors (TKIs) such as imatinib. The precise regulation of LSC stemness is incompletely understood. Given that traits of LSCs are subject to epigenetic regulation, we hypothesized that LSCs might be dependent on continuous active transcription of genes associated with super-enhancers (SEs), which might, in turn, suggest an opportunity for intervention. In this study, we tested this hypothesis and delineated the SE landscape in LSCs from patients with CML. Disruption of the SE-associated gene transcription by THZ1, a covalent cyclin-dependent kinase 7 (CDK7) inhibitor, efficiently eradicated LSCs in retroviral BCR-ABL­driven CML mice while sparing normal hematopoietic stem cells. Furthermore, we found that X-box binding protein 1 (XBP1), a substrate of mRNA-splicing endonuclease IRE1α in the unfolded protein response pathway, was an SE-associated oncogene in LSCs. Knockdown of XBP1 reduced survival and self-renewal capacity in primary CML CD34+ cells and eradicated LSCs in CML mice. Selectively blocking generation of the spliced form of Xbp1 by hematopoietic cell­specific Ire1 conditional knockout suppressed the progression of CML and impaired the leukemogenesis of LSCs in CML mice. Overall, we identified an epigenetic transcriptional program in LSCs, adding to evidence for the theory of "oncogene addiction" and suggesting a potential targeting strategy for CML.

CHEK1 and circCHEK1_246aa evoke chromosomal instability and induce bone lesion formation in multiple myeloma.

BACKGROUND: Multiple myeloma (MM) is still incurable and characterized by clonal expansion of plasma cells in the bone marrow (BM). Therefore, effective therapeutic interventions must target both myeloma cells and the BM niche. METHODS: Cell proliferation, drug resistance, and chromosomal instability (CIN) induced by CHEK1 were confirmed by Giemsa staining, exon sequencing, immunofluorescence and xenograft model in vivo. Bone lesion was evaluated by Tartrate-resistant acid phosphatase (TRAP) staining. The existence of circCHEK1_246aa was evaluated by qPCR, Sanger sequencing and Mass Spectrometer. RESULTS: We demonstrated that CHEK1 expression was significantly increased in human MM samples relative to normal plasma cells, and that in MM patients, high CHEK1 expression was associated with poor outcomes. Increased CHEK1 expression induced MM cellular proliferation and evoked drug-resistance in vitro and in vivo. CHEK1-mediated increases in cell proliferation and drug resistance were due in part to CHEK1-induced CIN. CHEK1 activated CIN, partly by phosphorylating CEP170. Interestingly, CHEK1 promoted osteoclast differentiation by upregulating NFATc1 expression. Intriguingly, we discovered that MM cells expressed circCHEK1_246aa, a circular CHEK1 RNA, which encoded and was translated to the CHEK1 kinase catalytic center. Transfection of circCHEK1_246aa increased MM CIN and osteoclast differentiation similarly to CHEK1 overexpression, suggesting that MM cells could secrete circCHEK1_246aa in the BM niche to increase the invasive potential of MM cells and promote osteoclast differentiation. CONCLUSIONS: Our findings suggest that targeting the enzymatic catalytic center encoded by CHEK1 mRNA and circCHEK1_246aa is a promising therapeutic modality to target both MM cells and BM niche.

Activation of transmembrane receptor tyrosine kinase DDR1-STAT3 cascade by extracellular matrix remodeling promotes liver metastatic colonization in uveal melanoma.

Colonization is believed a rate-limiting step of metastasis cascade. However, its underlying mechanism is not well understood. Uveal melanoma (UM), which is featured with single organ liver metastasis, may provide a simplified model for realizing the complicated colonization process. Because DDR1 was identified to be overexpressed in UM cell lines and specimens, and abundant pathological deposition of extracellular matrix collagen, a type of DDR1 ligand, was noted in the microenvironment of liver in metastatic patients with UM, we postulated the hypothesis that DDR1 and its ligand might ignite the interaction between UM cells and their surrounding niche of liver thereby conferring strengthened survival, proliferation, stemness and eventually promoting metastatic colonization in liver. We tested this hypothesis and found that DDR1 promoted these malignant cellular phenotypes and facilitated metastatic colonization of UM in liver. Mechanistically, UM cells secreted TGF-ß1 which induced quiescent hepatic stellate cells (qHSCs) into activated HSCs (aHSCs) which secreted collagen type I. Such a remodeling of extracellular matrix, in turn, activated DDR1, strengthening survival through upregulating STAT3-dependent Mcl-1 expression, enhancing stemness via upregulating STAT3-dependent SOX2, and promoting clonogenicity in cancer cells. Targeting DDR1 by using 7rh, a specific inhibitor, repressed proliferation and survival in vitro and in vivo outgrowth. More importantly, targeting cancer cells by pharmacological inactivation of DDR1 or targeting microenvironmental TGF-ß1-collagen I loop exhibited a prominent anti-metastasis effect in mice. In conclusion, targeting DDR1 signaling and TGF-ß signaling may be a novel approach to diminish hepatic metastasis in UM.

Arginine methyltransferase PRMT5 methylates and stabilizes KLF5 via decreasing its phosphorylation and ubiquitination to promote basal-like breast cancer.

Krüppel-like factor 5 (KLF5) is an oncogenic factor that is highly expressed in basal-like breast cancer (BLBC) and promotes cell proliferation, survival, migration, stemness, and tumor growth; however, its posttranslational modifications are poorly defined. Protein arginine methyltransferase 5 (PRMT5) is also an oncogene implicated in various carcinomas, including breast cancer. In this study, we found that PRMT5 interacts with KLF5 and catalyzes the di-methylation of KLF5 at Arginine 57 (R57) in a methyltransferase activity-dependent manner in BLBC cells. Depletion or pharmaceutical inhibition (using PJ-68) of PRMT5 decreased the expression of KLF5 and its downstream target genes in vitro and in vivo. PRMT5-induced KLF5R57me2 antagonizes GSK3ß-mediated KLF5 phosphorylation and subsequently Fbw7-mediated KLF5 ubiquitination and coupled degradation. Functionally, PRMT5 promotes breast cancer stem cell maintenance and proliferation, at least partially, by stabilizing KLF5. PRMT5 and KLF5 protein levels were positively correlated in clinical BLBCs. Taken together, PRMT5 methylates KLF5 to prevent its phosphorylation, ubiquitination, and degradation, and thus promotes breast cancer stem cell maintenance and proliferation. These findings suggest that PRMT5 is a potential therapeutic target for BLBC.

[A Review of the Roles of Endoplasmic Reticulum Stress in Cancer Cell Metastasis].

Metastasis is a multistep and low-efficiency biological process driven by acquisition of genetic and/or epigenetic alterations within tumor cells. These evolutionary alterations enable tumor cells to thrive in the inhospitable microenvironment they encounter in the process of metastasis and eventually lead to macroscopic metastases in distant organs. The unfolded protein response (UPR) induced by endoplasmic reticulum (ER) stress is one of the most important mechanisms regulating cellular adaptation to an adverse microenvironment. UPR is involved in all stages of metastasis, playing an important role in tumor cell growth, survival, and differentiation and the process of maintaining protein hemostasis. Sustained activation of ER stress sensors endows tumor cells with better epithelial-mesenchymal transition (EMT), survival, immune escape, angiogenesis, cellular adhesion, dormancy-to reactivation capacity in the process of metastasis. Here, we discussed the role of UPR in regulating the above-mentioned abilities of tumor cells during metastasis, providing a reference for development of new targets for the treatment of tumor metastasis.UPR in regulating the above-mentioned characteristics and mechanisms of tumor cells during metastasis, providing a reference for development of new targets for the treatment of tumor metastasis.

Erratum: Anthelmintic pyrvinium pamoate blocks Wnt/ß-catenin and induces apoptosis in multiple myeloma cells.

[This corrects the article DOI: 10.3892/ol.2018.8006.].

Erratum: The antihelminthic drug niclosamide effectively inhibits the malignant phenotypes of uveal melanoma in vitro and in vivo: Erratum.

[This corrects the article DOI: 10.7150/thno.17451.].

Verification of EZH2 as a druggable target in metastatic uveal melanoma.

BACKGROUND: Hepatic metastasis develops in ~ 50% of uveal melanoma (UM) patients with no effective treatments. Although GNAQ/GNA11 mutations are believed to confer pathogenesis of UM, the underlying mechanism of liver metastasis remains poorly understood. Given that profound epigenetic evolution may occur in the long journey of circulating tumor cells (CTCs) to distant organs, we hypothesized that EZH2 endowed tumor cells with enhanced malignant features (e.g., stemness and motility) during hepatic metastasis in UM. We aimed to test this hypothesis and explore whether EZH2 was a therapeutic target for hepatic metastatic UM patients. METHODS: Expression of EZH2 in UM was detected by qRT-PCR, Western blotting and immunohistochemistry staining. Proliferation, apoptosis, cancer stem-like cells (CSCs) properties, migration and invasion were evaluated under circumstances of treatment with either EZH2 shRNA or EZH2 inhibitor GSK126. Antitumor activity and frequency of CSCs were determined by xenografted and PDX models with NOD/SCID mice. Hepatic metastasis was evaluated with NOG mice. RESULTS: We found that EZH2 overexpressed in UM promoted the growth of UM; EZH2 increased the percentage and self-renewal of CSCs by miR-29c-DVL2-ß-catenin signaling; EZH2 facilitates migration and invasion of UM cells via RhoGDIγ-Rac1 axis. Targeting EZH2 either by genetics or small molecule inhibitor GSK126 decreased CSCs and motility and abrogated the liver metastasis of UM. CONCLUSIONS: These findings validate EZH2 as a druggable target in metastatic UM patients, and may shed light on the understanding and interfering the complicated metastatic process.