Targeting PRPK Function Blocks Colon Cancer Metastasis

Identification of 8 candidate microsatellite instability loci in colorectal cancer and validation of the ACVR2A mechanism in the tumor progression

This study probes the utility of biomarkers for microsatellite instability (MSI) detection and elucidates the molecular dynamics propelling colorectal cancer (CRC) progression. We synthesized a primer panel targeting 725 MSI loci, informed by The Cancer Genome Atlas (TCGA) and ancillary databases, to construct an amplicon library for next-generation sequencing (NGS). K-means clustering facilitated the distillation of 8 prime MSI loci, including activin A receptor type 2A (ACVR2A). Subsequently, we explored ACVR2A's influence on CRC advancement through in vivo tumor experiments and hematoxylin-eosin (HE) staining. Transwell assays gauged ACVR2A's role in CRC cell migration and invasion, while colony formation assays appraised cell proliferation. Western blotting illuminated the impact of ACVR2A suppression on CRC's PI3K/AKT/mTOR pathway protein expressions under hypoxia. Additionally, ACVR2A's influence on CRC-induced angiogenesis was quantified via angiogenesis assays. K-means clustering of NGS data pinpointed 32 MSI loci specific to tumor and DNA mismatch repair deficiency (dMMR) tissues. ACVR2A emerged as a pivotal biomarker, discerning MSI-H tissues with 90.97% sensitivity. A curated 8-loci set demonstrated 100% sensitivity and specificity for MSI-H detection in CRC. In vitro analyses corroborated ACVR2A's critical role, revealing its suppression of CRC proliferation, migration, and invasion. Moreover, ACVR2A inhibition under CRC-induced hypoxia markedly escalated MMP3, CyclinA, CyclinD1, and HIF1α protein expressions, alongside angiogenesis, by triggering the PI3K/AKT/mTOR cascade. The 8-loci ensemble stands as the optimal marker for MSI-H identification in CRC. ACVR2A, a central element within this group, deters CRC progression, while its suppression amplifies PI3K/AKT/mTOR signaling and angiogenesis under hypoxic stress.

Progression of monoclonal gammopathy of undetermined significance to multiple myeloma is associated with enhanced translational quality control and overall loss of surface antigens

BACKGROUND

Despite significant advancements in treatment strategies, multiple myeloma remains incurable. Additionally, there is a distinct lack of reliable biomarkers that can guide initial treatment decisions and help determine suitable replacement or adjuvant therapies when relapse ensues due to acquired drug resistance.

METHODS

To define specific proteins and pathways involved in the progression of monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM), we have applied super-SILAC quantitative proteomic analysis to CD138 + plasma cells from 9 individuals with MGUS and 37 with MM.

RESULTS

Unsupervised hierarchical clustering defined three groups: MGUS, MM, and MM with an MGUS-like proteome profile (ML) that may represent a group that has recently transformed to MM. Statistical analysis identified 866 differentially expressed proteins between MM and MGUS, and 189 between MM and ML, 177 of which were common between MGUS and ML. Progression from MGUS to MM is accompanied by upregulated EIF2 signaling, DNA repair, and proteins involved in translational quality control, whereas integrin- and actin cytoskeletal signaling and cell surface markers are downregulated.

CONCLUSION

Compared to the premalignant plasma cells in MGUS, malignant MM cells apparently have mobilized several pathways that collectively contribute to ensure translational fidelity and to avoid proteotoxic stress, especially in the ER. The overall reduced expression of immunoglobulins and surface antigens contribute to this and may additionally mediate evasion from recognition by the immune apparatus. Our analyses identified a range of novel biomarkers with potential prognostic and therapeutic value, which will undergo further evaluation to determine their clinical significance.

Enitociclib, a Selective CDK9 Inhibitor, Induces Complete Regression of MYC+ Lymphoma by Downregulation of RNA Polymerase II Mediated Transcription

Double-hit diffuse large B-cell lymphoma (DH-DLBCL) is an aggressive, and often refractory, type of B-cell non-Hodgkin lymphoma (NHL) characterized by rearrangements in MYC and BCL2. Cyclin-dependent kinase 9 (CDK9) regulates transcriptional elongation and activation of transcription factors, including MYC, making it a potential targeted approach for the treatment of MYC+ lymphomas. Enitociclib is a well-tolerated and clinically active CDK9 inhibitor leading to complete metabolic remissions in 2 of 7 patients with DH-DLBCL treated with once weekly 30 mg intravenous administration. Herein, we investigate the pharmacodynamic effect of CDK9 inhibition in preclinical models and in blood samples from patients [DH-DLBCL (n = 10) and MYC+ NHL (n = 5)] treated with 30 mg i.v. once weekly enitociclib. Enitociclib shows significant regulation of RNA polymerase II Ser2 phosphorylation in a MYC-amplified SU-DHL-4 cell line and depletion of MYC and antiapoptosis protein MCL1 in SU-DHL-4 and MYC-overexpressing SU-DHL-10 cell lines in vitro. Tumor growth inhibition reaching 0.5% of control treated SU-DHL-10 xenografts is achieved in vivo and MYC and MCL1 depletion as well as evidence of apoptosis activation after enitociclib treatment is demonstrated. An unbiased analysis of the genes affected by CDK9 inhibition in both cell lines demonstrates that RNA polymerase II and transcription pathways are primarily affected and novel enitociclib targets such as PHF23 and TP53RK are discovered. These findings are recapitulated in blood samples from enitociclib-treated patients; while MYC downregulation is most robust with enitociclib treatment, other CDK9-regulated targets may be MYC independent delivering a transcriptional downregulation via RNA polymerase II.

SIGNIFICANCE

MYC+ lymphomas are refractory to standard of care and novel treatments that downregulate MYC are needed. The utility of enitociclib, a selective CDK9 inhibitor in this patient population, is demonstrated in preclinical models and patients. Enitociclib inhibits RNA polymerase II function conferring a transcriptional shift and depletion of MYC and MCL1. Enitociclib intermittent dosing downregulates transcription factors including MYC, providing a therapeutic window for durable responses in patients with MYC+ lymphoma.

TP53RK Drives the Progression of Chronic Kidney Disease by Phosphorylating Birc5

Renal fibrosis is a common characteristic of various chronic kidney diseases (CKDs) driving the loss of renal function. During this pathological process, persistent injury to renal tubular epithelial cells and activation of fibroblasts chiefly determine the extent of renal fibrosis. In this study, the role of tumor protein 53 regulating kinase (TP53RK) in the pathogenesis of renal fibrosis and its underlying mechanisms is investigated. TP53RK is upregulated in fibrotic human and animal kidneys with a positive correlation to kidney dysfunction and fibrotic markers. Interestingly, specific deletion of TP53RK either in renal tubule or in fibroblasts in mice can mitigate renal fibrosis in CKD models. Mechanistic investigations reveal that TP53RK phosphorylates baculoviral IAP repeat containing 5 (Birc5) and facilitates its nuclear translocation; enhanced Birc5 displays a profibrotic effect possibly via activating PI3K/Akt and MAPK pathways. Moreover, pharmacologically inhibiting TP53RK and Birc5 using fusidic acid (an FDA-approved antibiotic) and YM-155(currently in clinical phase 2 trials) respectively both ameliorate kidney fibrosis. These findings demonstrate that activated TP53RK/Birc5 signaling in renal tubular cells and fibroblasts alters cellular phenotypes and drives CKD progression. A genetic or pharmacological blockade of this axis serves as a potential strategy for treating CKDs.

Pro-inflammatory polarization and colorectal cancer modulate alternative and intronic polyadenylation in primary human macrophages

Introduction

Macrophages are essential cells of the immune system that alter their inflammatory profile depending on their microenvironment. Alternative polyadenylation in the 3'UTR (3'UTR-APA) and intronic polyadenylation (IPA) are mechanisms that modulate gene expression, particularly in cancer and activated immune cells. Yet, how polarization and colorectal cancer (CRC) cells affect 3'UTR-APA and IPA in primary human macrophages was unclear.

Methods

In this study, we isolated primary human monocytes from healthy donors, differentiated and polarized them into a pro-inflammatory state and performed indirect co-cultures with CRC cells. ChrRNA-Seq and 3'RNA-Seq was performed to quantify gene expression and characterize new 3'UTR-APA and IPA mRNA isoforms.

Results

Our results show that polarization of human macrophages from naïve to a pro-inflammatory state causes a marked increase of proximal polyA site selection in the 3'UTR and IPA events in genes relevant to macrophage functions. Additionally, we found a negative correlation between differential gene expression and IPA during pro-inflammatory polarization of primary human macrophages. As macrophages are abundant immune cells in the CRC microenvironment that either promote or abrogate cancer progression, we investigated how indirect exposure to CRC cells affects macrophage gene expression and 3'UTR-APA and IPA events. Co-culture with CRC cells alters the inflammatory phenotype of macrophages, increases the expression of pro-tumoral genes and induces 3'UTR-APA alterations. Notably, some of these gene expression differences were also found in tumor-associated macrophages of CRC patients, indicating that they are physiologically relevant. Upon macrophage pro-inflammatory polarization, SRSF12 is the pre-mRNA processing gene that is most upregulated. After SRSF12 knockdown in M1 macrophages there is a global downregulation of gene expression, in particular in genes involved in gene expression regulation and in immune responses.

Discussion

Our results reveal new 3'UTR-APA and IPA mRNA isoforms produced during pro-inflammatory polarization of primary human macrophages and CRC co-culture that may be used in the future as diagnostic or therapeutic tools. Furthermore, our results highlight a function for SRSF12 in pro-inflammatory macrophages, key cells in the tumor response.

Patent highlights December 2021-January 2022

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Phosphorylation of PBK/TOPK Tyr74 by JAK2 promotes Burkitt lymphoma tumor growth

Burkitt lymphoma (BL), which is characterized by high invasiveness, is a subgroup of non-Hodgkin lymphoma. Although BL is regarded as a highly curable disease, especially for children, some patients unfortunately still do not respond adequately. The understanding of the etiology and molecular mechanisms of BL is still limited, and targeted therapies are still lacking. Here, we found that T-LAK cell-derived protein kinase (TOPK) and phosphorylated Janus kinase 2 (p-JAK2) are highly expressed in the tissues of BL patients. We report that TOPK directly binds to and is phosphorylated at Tyr74 by JAK2. Histone H3, one of the downstream targets of TOPK, is also phosphorylated in vivo and in vitro. Furthermore, we report that the phosphorylation of TOPK at Tyr74 by JAK2 plays a vital role in the proliferation of BL cells and promotes BL tumorigenesis in vivo. Phosphorylation of TOPK at Tyr74 by JAK2 enhances the stability of TOPK. Collectively, our results suggest that the JAK2/TOPK/histone H3 axis plays a key role in the proliferation of BL cells and BL tumorigenesis in vivo.

LncRNA SNHG12 promotes the development and progression of colon cancer by regulating the miR-15a/PDK4 axis

Colon cancer is a common gastrointestinal tumor with complex pathological process. Recently, the relationship between long non-coding RNA (lncRNA) and colon cancer has attracted more and more attention, whereas the underlying molecular mechanism is still poorly understood. Here, we found that the expression of lncRNA small nucleolar RNA host gene 12 (SNHG12) was markedly upregulated in colon cancer samples compared to normal adjacent tissues. Notably, patients with low expression of SNHG12 displayed higher survival rate than those with high expression of SNHG12. Further researches revealed that knockdown of SNHG12 suppressed the malignant phenotype of colon cancer cells. Interestingly, SNHG12 could function as a sponge to specifically bind to microRNA-15a (miR-15a). Moreover, we confirmed that pyruvate dehydrogenase kinase 4 (PDK4) is a direct target gene of miR-15a. Finally, inhibiting miR-15a expression largely abolished the effect of SNHG12 silencing on colon cancer cells. In conclusion, our data uncovered the critical role of SNHG12 in the development and progression of colon cancer through regulating the miR-15a/PDK4 axis, therefore providing a promising target for treating this disease.

Access to New Cytotoxic Triterpene and Steroidal Acid-TEMPO Conjugates by Ugi Multicomponent-Reactions

Multicomponent reactions, especially the Ugi-four component reaction (U-4CR), provide powerful protocols to efficiently access compounds having potent biological and pharmacological effects. Thus, a diverse library of betulinic acid (BA), fusidic acid (FA), cholic acid (CA) conjugates with TEMPO (nitroxide) have been prepared using this approach, which also makes them applicable in electron paramagnetic resonance (EPR) spectroscopy. Moreover, convertible amide modified spin-labelled fusidic acid derivatives were selected for post-Ugi modification utilizing a wide range of reaction conditions which kept the paramagnetic center intact. The nitroxide labelled betulinic acid analogue 6 possesses cytotoxic effects towards two investigated cell lines: prostate cancer PC3 (IC₅₀ 7.4 ± 0.7 μM) and colon cancer HT29 (IC₅₀ 9.0 ± 0.4 μM). Notably, spin-labelled fusidic acid derivative 8 acts strongly against these two cancer cell lines (PC3: IC₅₀ 6.0 ± 1.1 μM; HT29: IC₅₀ 7.4 ± 0.6 μM). Additionally, another fusidic acid analogue 9 was also found to be active towards HT29 with IC₅₀ 7.0 ± 0.3 μM (CV). Studies on the mode of action revealed that compound 8 increased the level of caspase-3 significantly which clearly indicates induction of apoptosis by activation of the caspase pathway. Furthermore, the exclusive mitochondria targeting of compound 18 was successfully achieved, since mitochondria are the major source of ROS generation.

Crystal structure of the human PRPK-TPRKB complex

Mutations of the p53-related protein kinase (PRPK) and TP53RK-binding protein (TPRKB) cause Galloway-Mowat syndrome (GAMOS) and are found in various human cancers. We have previously shown that small compounds targeting PRPK showed anti-cancer activity against colon and skin cancer. Here we present the 2.53 Å crystal structure of the human PRPK-TPRKB-AMPPNP (adenylyl-imidodiphosphate) complex. The structure reveals details in PRPK-AMPPNP coordination and PRPK-TPRKB interaction. PRPK appears in an active conformation, albeit lacking the conventional kinase activation loop. We constructed a structural model of the human EKC/KEOPS complex, composed of PRPK, TPRKB, OSGEP, LAGE3, and GON7. Disease mutations in PRPK and TPRKB are mapped into the structure, and we show that one mutation, PRPK K238Nfs*2, lost the binding to OSGEP. Our structure also makes the virtual screening possible and paves the way for more rational drug design.

Jian Li and Xinli Ma et al. present a 2.53 Å crystal structure of a complex consisting of the human p53-related protein kinase (PRPK), TP53RK-binding protein, and adenylyl-imidodiphosphate. They find that one disease mutation, PRPK K238Nfs*2, is important for PRPK’s binding to O-sialoglycoprotein endopeptidase, providing insights into rational drug design.

LIN28B promotes neuroblastoma metastasis and regulates PDZ binding kinase

Neuroblastoma is an aggressive pediatric malignancy of the neural crest with suboptimal cure rates and a striking predilection for widespread metastases, underscoring the need to identify novel therapeutic vulnerabilities. We recently identified the RNA binding protein LIN28B as a driver in high-risk neuroblastoma and demonstrated it promotes oncogenic cell proliferation by coordinating a RAN-Aurora kinase A network. Here, we demonstrate that LIN28B influences another key hallmark of cancer, metastatic dissemination. Using a murine xenograft model of neuroblastoma dissemination, we show that LIN28B promotes metastasis. We demonstrate that this is in part due to the effects of LIN28B on self-renewal and migration, providing an understanding of how LIN28B shapes the metastatic phenotype. Our studies reveal that the let-7 family, which LIN28B inhibits, decreases self-renewal and migration. Next, we identify PDZ Binding Kinase (PBK) as a novel LIN28B target. PBK is a serine/threonine kinase that promotes the proliferation and self-renewal of neural stem cells and serves as an oncogenic driver in multiple aggressive malignancies. We demonstrate that PBK is both a novel direct target of let-7i and that MYCN regulates PBK expression, thus elucidating two oncogenic drivers that converge on PBK. Functionally, PBK promotes self-renewal and migration, phenocopying LIN28B. Taken together, our findings define a role for LIN28B in neuroblastoma metastasis and define the targetable kinase PBK as a potential novel vulnerability in metastatic neuroblastoma.

Acetylshikonin suppressed growth of colorectal tumour tissue and cells by inhibiting the intracellular kinase, T-lymphokine-activated killer cell-originated protein kinase

BACKGROUND AND PURPOSE

Overexpression or aberrant activation of the T-lymphokine-activated killer cell-originated protein kinase (TOPK) promotes gene expression and growth of solid tumours, implying that TOPK would be a rational target in developing novel anticancer drugs. Acetylshikonin, a diterpenoid compound isolated from Lithospermum erythrorhizon root, exerts a range of biological activities. Here we have investigated whether acetylshikonin, by acting as an inhibitor of TOPK, can attenuate the proliferation of colorectal cancer cells and the growth of patient-derived tumours, in vitro and in vivo.

EXPERIMENTAL APPROACH

Targets of acetylshikonin, were identified using kinase profiling analysis, kinetic/binding assay, and computational docking analysis and knock-down techniques. Effects of acetylshikonin on colorectal cancer growth and the underlying mechanisms were evaluated in cell proliferation assays, propidium iodide and annexin-V staining analyses and western blots. Patient-derived tumour xenografts in mice (PDX) and immunohistochemistry were used to assess anti-tumour effects of acetylshikonin.

KEY RESULTS

Acetylshikonin directly inhibited TOPK activity, interacting with the ATP-binding pocket of TOPK. Acetylshikonin suppressed cell proliferation by inducing cell cycle arrest at the G1 phase, stimulated apoptosis, and increased the expression of apoptotic biomarkers in colorectal cancer cell lines. Mechanistically, acetylshikonin diminished the phosphorylation and activation of TOPK signalling. Furthermore, acetylshikonin decreased the volume of PDX tumours and reduced the expression of TOPK signalling pathway in xenograft tumours.

CONCLUSION AND IMPLICATIONS

Acetylshikonin suppressed growth of colorectal cancer cells by attenuating TOPK signalling. Targeted inhibition of TOPK by acetylshikonin might be a promising new approach to the treatment of colorectal cancer.

The function of Piezo1 in colon cancer metastasis and its potential regulatory mechanism

OBJECTIVE

Increasing evidence has revealed that mechanical stress and elevated mechanical signals promote malignant tumor transformation and metastasis. This study aimed to explore the function of the mechanically activated ion-channel Piezo1 in the colon cancer metastasis and its potential regulatory mechanism.

METHODS

First, we examined the expression levels of Piezo1 and mitochondrial calcium uniporter (MCU) both in colon cancer tissues and assessed the prognostic value of Piezo1 and MCU in a colon cancer cohort (n = 110). Second, functional assays were performed to investigate the effects of Piezo1 and MCU on colon cancer cell migration, invasion, and mitochondrial membrane potential. Third, we analyzed the expression of Piezo1, MCU, and HIF-1α by overexpressing/silencing each other's expression.

RESULTS

We found that Piezo1 was up-regulated and MCU was down-regulated in colon cancer tissues. Piezo1 and MCU were both correlated with poor prognosis of patients with colon cancer. Overexpressing Piezo1 and silencing MCU could promote colon cancer cell migration and metastasis, reduce mitochondrial membrane potential, and promote each other's expression. We also found that HIF-1α was up-regulated in colon cancer tissues. Additionally, silencing Piezo1 inhibited the expression of HIF-1α and VEGF, which was contrary to MCU silencing. Intriguingly, Piezo1-overexpressing cells did not regain their migration behaviors when HIF-1α expression was inhibited, which was accompanied with the re-expression of MCU and VEGF.

CONCLUSION

In our study, Piezo1 is involved in colon cancer cell metastasis. Furthermore, our findings indicated a possible Piezo1-MCU-HIF-1α-VEGF axis, which still need further exploration.

Evaluating the influence of common antibiotics on the efficacy of a recombinant immunotoxin in tissue culture

OBJECTIVE

Recombinant immunotoxins (RITs) are antibody-toxin fusion proteins that can selectively eliminate populations of cells expressing specific surface receptors. They are in evaluation as therapeutic agents for cancer. RITs based on Pseudomonas exotoxin A (PE) are in use clinically for the treatment of hairy cell leukemia, and under trial for the treatment of other cancers. In an effort to improve the efficacy of PE-based RITs, we evaluated the potential of combination therapy with several common antibiotics (tetracycline, chloramphenicol, streptomycin, linezolid, fusidic acid, and kanamycin) on human cell lines HEK293, OVCAR8, and CA46. Antibiotics were selected based on their potential to inhibit mitochondrial protein synthesis and disrupt energy metabolism in cancer cells.

RESULTS

Tetracycline, chloramphenicol, linezolid, and fusidic acid alone killed cultured human cells at high concentrations. At high but nontoxic concentrations of each antibiotic, only chloramphenicol treatment of the Burkitt's lymphoma cell line CA46 showed enhanced cytotoxicity when paired with an anti-transferrin receptor/PE RIT. This result, however, could not be replicated in additional Burkitt's lymphoma cell lines Ramos and Raji. Although the six antibiotics we tested are not promising candidates for RIT combination therapy, we suggest that fusidic acid could be considered independently as a potential cancer therapeutic.

T-LAK cell-originated protein kinase (TOPK): an emerging target for cancer-specific therapeutics

'Targeted' or 'biological' cancer treatments rely on differential gene expression between normal tissue and cancer, and genetic changes that render tumour cells especially sensitive to the agent being applied. Problems exist with the application of many agents as a result of damage to local tissues, tumour evolution and treatment resistance, or through systemic toxicity. Hence, there is a therapeutic need to uncover specific clinical targets which enhance the efficacy of cancer treatment whilst minimising the risk to healthy tissues. T-LAK cell-originated protein kinase (TOPK) is a MAPKK-like kinase which plays a role in cell cycle regulation and mitotic progression. As a consequence, TOPK expression is minimal in differentiated cells, although its overexpression is a pathophysiological feature of many tumours. Hence, TOPK has garnered interest as a cancer-specific biomarker and biochemical target with the potential to enhance cancer therapy whilst causing minimal harm to normal tissues. Small molecule inhibitors of TOPK have produced encouraging results as a stand-alone treatment in vitro and in vivo, and are expected to advance into clinical trials in the near future. In this review, we present the current literature pertaining to TOPK as a potential clinical target and describe the progress made in uncovering its role in tumour development. Firstly, we describe the functional role of TOPK as a pro-oncogenic kinase, followed by a discussion of its potential as a target for the treatment of cancers with high-TOPK expression. Next, we provide an overview of the current preclinical progress in TOPK inhibitor discovery and development, with respect to future adaptation for clinical use.