PAK Kinase Inhibition Has Therapeutic Activity in Novel Preclinical Models of Adult T-Cell Leukemia/Lymphoma

Targeting P21-activated kinase suppresses proliferation and enhances chemosensitivity in T-cell lymphoblastic lymphoma

T-cell lymphoblastic lymphoma (T-LBL) is a highly aggressive non-Hodgkin lymphoma with a poor prognosis. P21-activated kinase (PAK) is a component of the gene expression-based classifier that can predict the prognosis of T-LBL. However, the role of PAK in T-LBL progression and survival remains poorly understood. Herein, we found that the expression of PAK1 was significantly higher in T-LBL cell lines (Jurkat, SUP-T1, and CCRF-CEM) compared to the human T-lymphoid cell line. Moreover, PAK2 mRNA level of 32 relapsed T-LBL patients was significantly higher than that of 37 cases without relapse (P = .012). T-LBL patients with high PAK1 and PAK2 expression had significantly shorter median RFS than those with low PAK1 and PAK2 expression (PAK1, P = .028; PAK2, P = .027; PAK1/2, P = .032). PAK inhibitors, PF3758309 (PF) and FRAX597, could suppress the proliferation of T-LBL cells by blocking the G1/S cell cycle phase transition. Besides, PF could enhance the chemosensitivity to doxorubicin in vitro and in vivo. Mechanistically, through western blotting and RNA sequencing, we identified that PF could inhibit the phosphorylation of PAK1/2 and downregulate the expression of cyclin D1, NF-κB and cell adhesion signaling pathways in T-LBL cell lines. These findings suggest that PAK might be associated with T-LBL recurrence and further found that PAK inhibitors could suppress proliferation and enhance chemosensitivity of T-LBL cells treated with doxorubicin. Collectively, our present study underscores the potential therapeutic effect of inhibiting PAK in T-LBL therapy.

Acetyl transferase EP300 deficiency leads to chronic replication stress mediated by defective fork protection at stalled replication forks

Mutations in the epigenetic regulator and global transcriptional activator, E1A binding protein (EP300), is being increasingly reported in aggressive hematological malignancies including adult T-cell leukemia/lymphoma (ATLL). However, the mechanistic contribution of EP300 dysregulation to cancer initiation and progression are currently unknown. Independent inhibition of EP300 in human cells results in the differential expression of genes involved in regulating the cell cycle, DNA replication and DNA damage response. Nevertheless, specific function played by EP300 in DNA replication initiation, progression and replication fork integrity has not been studied. Here, using ATLL cells as a model to study EP300 deficiency and an p300-selective PROTAC degrader, degrader as a pharmacologic tool, we reveal that EP300-mutated cells display prolonged cell cycle kinetics, due to pronounced dysregulations in DNA replication dynamics leading to persistent genomic instability. Aberrant DNA replication in EP300-mutated cells is characterized by elevated replication origin firing due to increased replisome pausing genome-wide. We demonstrate that EP300 deficiency results in nucleolytic degradation of nascently synthesized DNA at stalled forks due to a prominent defect in fork stabilization and protection. This in turn results in the accumulation of single stranded DNA gaps at collapsed replication forks, in EP300-deficient cells. Inhibition of Mre11 nuclease rescues the ssDNA accumulation indicating a dysregulation in downstream mechanisms that restrain nuclease activity at stalled forks. Importantly, we find that the absence of EP300 results in decreased expression of BRCA2 protein expression and a dependency on POLD3-mediated error-prone replication restart mechanisms. The overall S-phase abnormalities observed lead to under-replicated DNA in G2/M that instigates mitotic DNA synthesis. This in turn is associated with mitotic segregation defects characterized by elevated micronuclei formation, accumulation of cytosolic DNA and transmission of unrepaired inherited DNA lesions in the subsequent G1-phase in EP300-deficient cells. We demonstrate that the DNA replication dynamics of EP300-mutated cells ATLL cells recapitulate features of BRCA-deficient cancers. Altogether these results suggest that mutations in EP300 cause chronic DNA replication stress and defective replication fork restart results in persistent genomic instability that underlie aggressive chemo-resistant tumorigenesis in humans.

PAK and PI3K pathway activation confers resistance to KRASG12C inhibitor sotorasib

BACKGROUND

KRAS is a frequently mutated oncogene in human cancer. Clinical studies on the covalent inhibitors of the KRASG12C mutant have reported promising results. However, primary and acquired resistance may limit their clinical use.

METHODS

Sotorasib-resistant cell lines were established. We explored the signalling pathways activated in these resistant cell lines and their roles in sotorasib resistance.

RESULTS

The resistant cells exhibited increased cell-matrix adhesion with increased levels of stress fibres and focal adherens. p21-activated kinases (PAKs) were activated in resistant cells, which phosphorylate MEK at serine 298 of MEK and serine 338 of c-Raf to activate the mitogen-activated protein kinase pathway. The PAK inhibitors FRAX597 and FRAX486 in synergy with sotorasib reduced the viability of KRASG12C mutant cancer cells. Furthermore, the PI3K/AKT pathway was constitutively active in sotorasib-resistant cells. The overexpression of constitutively activated PI3K or the knockdown of PTEN resulted in resistance to sotorasib. PI3K inhibitor alpelisib was synergistic with sotorasib in compromising the viability of KRASG12C mutant cancer cells. Moreover, PI3K and PAK pathways formed a mutual positive regulatory loop that mediated sotorasib resistance.

CONCLUSIONS

Our results indicate that the cell-matrix interaction-dependent activation of PAK mediates resistance to sotorasib through the activation of MAPK and PI3K pathways.

The oncogenic driving force of CD30 signaling-induced chromosomal instability in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) develops via stepwise accumulation of gene mutations and chromosome aberrations. However, the molecular mechanisms underlying this tumorigenic process are poorly understood. We previously reported the presence of a biological link between the expression of CD30, which serves as a marker for ATL progression, and the actively proliferating fraction of human T-cell leukemia virus type 1 (HTLV-1)-infected cells that display polylobulation. Here, we demonstrated that CD30 signaling induced chromosomal instability with clonal expansion through DNA double-strand breaks (DSBs) via an increase of intracellular reactive oxygen species. CD30⁺ ATL cells were composed of subclones with additional genomic aberrations compared with CD30^- ATL cells in ATL patients. Furthermore, we found an accumulation of copy number loss of DSB repair-related genes as the disease progressed. Taken together, CD30 expression on ATL cells appears to be correlated with genomic instability, suggesting that CD30 signaling is one of the oncogenic factors of ATL progression with clonal evolution. This study provides new insight into the biological roles of CD30 signaling and could improve our understanding of tumorigenic processes of HTLV-1-infected cells.

Up-regulation of the PI3K/AKT and RHO/RAC/PAK signalling pathways in CHK1 inhibitor resistant Eµ-Myc lymphoma cells

The development of resistance and the activation of bypass pathway signalling represents a major problem for the clinical application of protein kinase inhibitors. While investigating the effect of either a c-Rel deletion or RelAT505A phosphosite knockin on the Eµ-Myc mouse model of B-cell lymphoma, we discovered that both NF-κB subunit mutations resulted in CHK1 inhibitor resistance, arising from either loss or alteration of CHK1 activity, respectively. However, since Eµ-Myc lymphomas depend on CHK1 activity to cope with high levels of DNA replication stress and consequent genomic instability, it was not clear how these mutant NF-κB subunit lymphomas were able to survive. To understand these survival mechanisms and to identify potential compensatory bypass signalling pathways in these lymphomas, we applied a multi-omics strategy. With c-Rel-/- Eµ-Myc lymphomas we observed high levels of Phosphatidyl-inositol 3-kinase (PI3K) and AKT pathway activation. Moreover, treatment with the PI3K inhibitor Pictilisib (GDC-0941) selectively inhibited the growth of reimplanted c-Rel-/- and RelAT505A, but not wild type (WT) Eµ-Myc lymphomas. We also observed up-regulation of a RHO/RAC pathway gene expression signature in both Eµ-Myc NF-κB subunit mutation models. Further investigation demonstrated activation of the RHO/RAC effector p21-activated kinase (PAK) 2. Here, the PAK inhibitor, PF-3758309 successfully overcame resistance of RelAT505A but not WT lymphomas. These findings demonstrate that up-regulation of multiple bypass pathways occurs in CHK1 inhibitor resistant Eµ-Myc lymphomas. Consequently, drugs targeting these pathways could potentially be used as either second line or combinatorial therapies to aid the successful clinical application of CHK1 inhibitors.

Recent advances on development of p21-activated kinase 4 inhibitors as anti-tumor agents

The p21-activated kinase 4 (PAK4) is a member of the PAKs family. It is overexpressed in multiple tumor tissues. Pharmacological inhibition of PAK4 attenuates proliferation, migration, and invasion of cancer cells. Recent studies revealed that inhibition of PAK4 sensitizes immunotherapy which has been extensively exploited as a new strategy to treat cancer. In the past few years, a large number of PAK4 inhibitors have been reported. Of note, the allosteric inhibitor KPT-9274 has been tested in phase Ⅰ clinic trials. Herein, we provide an update on recent research progress on the PAK4 mediated signaling pathway and highlight the development of the PAK4 small molecular inhibitors in recent 5 years. Meanwhile, challenges, limitations, and future developmental directions will be discussed as well.

Regulation of human T-cell leukemia virus type 1 antisense promoter by myocyte enhancer factor-2C in the context of adult T-cell leukemia and lymphoma

Adult T-cell leukemia and lymphoma (ATLL) is an intractable T-cell neoplasia caused by a retrovirus, namely human T-cell leukemia virus type 1 (HTLV-1). Patients suffering from ATLL present a poor prognosis and have a dearth of treatment options. In contrast to the sporadic expression of viral transactivator protein Tax present at the 5' promoter region long terminal repeats (LTR), HTLV-1 bZIP gene (HBZ) is encoded by 3'LTR (the antisense promoter) and maintains its constant expression in ATLL cells and patients. The antisense promoter is associated with selective retroviral gene expression and has been an understudied phenomenon. Herein, we delineate the activity of transcription factor MEF (myocyte enhancer factor)-2 family members, which were found to be enriched at the 3'LTR and play an important role in the pathogenesis of ATLL. Of the four MEF isoforms (A to D), MEF-2A and 2C were highly overexpressed in a wide array of ATLL cell lines and in acute ATLL patients. The activity of MEF-2 isoforms were determined by knockdown experiments that led to decreased cell proliferation and regulated cell cycle progression. High enrichment of MEF-2C was observed at the 3'LTR along with cofactors Menin and JunD resulting in binding of MEF-2C to HBZ at this region. Chemical inhibition of MEF-2 proteins resulted in the cytotoxicity of ATLL cells in vitro and reduction of proviral load in a humanized mouse model. Taken together, this study provides a novel mechanism of 3'LTR regulation and establishes MEF-2 signaling a potential target for therapeutic intervention for ATLL.

The Combined Use of Orf Virus and PAK4 Inhibitor Exerts Anti-tumor Effect in Breast Cancer

The parapoxvirus Orf virus (ORFV) has long been recognized as one of the valuable vectors in researches of oncolytic virus. In order to develop a potential therapeutic strategy for breast cancer based on the oncolytic virotherapy via ORFV, firstly we explore the oncolytic effects of ORFV. Our research showed that ORFV exerts anti-tumor effects in vitro by inducing breast cancer cell G2/M phase arrest and cell apoptosis. In vivo experiments were carried out, in which we treated 4T1 tumor-bearing BALB/C mice via intratumoral injection of ORFV. ORFV can exert anti-tumor activity by regulating tumor microenvironment (TME) and inducing a host immune response plus directly oncolytic effect. The CRISPR-Cas9 knockout library targeting 507 kinases was used to screen out PAK4, which is beneficial to the anti-tumor effect of ORFV on breast cancer cells. PF-3758309 is a potent PAK4-targeted inhibitor. Co-using of ORFV and PF-3758309 as a combination treatment produces its anti-tumor effects through inhibition of cell viability, induction of apoptosis and suppression of cell migration and invasion in vitro. The results of in vivo experiments showed that the tumor growth of mice in the combination treatment group was significantly inhibited, which proved that the combination treatment exerts an effective anti-tumor effect in vivo. In summary, we have clarified the oncolytic effect of ORFV on breast cancer, and found that the combination of ORFV and PAK4 inhibitor can effectively improve the oncolytic effect of ORFV. We hope our research could provide a new idea for the development of new treatment strategies for breast cancer.

p21-Activated kinases as promising therapeutic targets in hematological malignancies

The p21-Activated Kinases (PAKs) are a family of six serine/threonine kinases that were originally identified as downstream effectors of the Rho GTPases Cdc42 and Rac. Since the first PAK was discovered in 1994, studies have revealed their fundamental and biological importance in the development of physiological systems. Within the cell, PAKs also play significant roles in regulating essential cellular processes such as cytoskeletal dynamics, gene expression, cell survival, and cell cycle progression. These processes are often deregulated in numerous cancers when different PAKs are overexpressed or amplified at the chromosomal level. Furthermore, PAKs modulate multiple oncogenic signaling pathways which facilitate apoptosis escape, uncontrolled proliferation, and drug resistance. There is growing insight into the critical roles of PAKs in regulating steady-state hematopoiesis, including the properties of hematopoietic stem cells (HSC), and the initiation and progression of hematological malignancies. This review will focus on the most recent studies that provide experimental evidence showing how specific PAKs regulate the properties of leukemic stem cells (LSCs) and drug-resistant cells to initiate and maintain hematological malignancies. The current understanding of the molecular and cellular mechanisms by which the PAKs operate in specific human leukemia or lymphomas will be discussed. From a translational point of view, PAKs have been suggested to be critical therapeutic targets and potential prognosis markers; thus, this review will also discuss current therapeutic strategies against hematological malignancies using existing small-molecule PAK inhibitors, as well as promising combination treatments, to sensitize drug-resistant cells to conventional therapies. The challenges of toxicity and non-specific targeting associated with some PAK inhibitors, as well as how future approaches for PAK inhibition to overcome these limitations, will also be addressed.

Analysis of therapeutic targets and prognostic biomarkers of CXC chemokines in cervical cancer microenvironment

Background

The tumor microenvironment (TME) has received an increasing amount of attention. CXC chemokines can regulate immune cell transport and tumor cell activity to exert anti-tumor immunity. However, studies on the expression and prognosis of CXC chemokines in cervical cancer (CC) are more limited.

Methods

The study investigated the role of CXC chemokines in TME of CC by using public databases. Moreover, quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC) of CXC chemokines were performed to further verify.

Results

The transcriptional levels of CXCL1/3/5/6/8/9/10/11/13/16/17 in CC tissues were significantly elevated while the transcriptional levels of CXCL12/14 were significantly reduced. We reached a consistent conclusion that the expression of CXCL9/10/11/13 was verified by quantitative real-time PCR and immunohistochemistry. Moreover, CC patients with low transcriptional levels of CXCL1/2/3/4/5/8 were significantly associated with longer overall survival (OS). The CCL family was related to CXC chemokines neighboring alteration. RELA, NFKB1, LCK and PAK2 were the key transcription factors and kinase targets of CXC chemokines, respectively. We also found there were significant correlations between the expression of CXCL9/10/11 and the infiltration of immune cells (CD8+ T cell, CD4+ T cell, neutrophils and dendritic cells).

Conclusions

In brief, we conducted a comprehensive analysis of CXC chemokines via clinical data and some online public databases. Our results may provide a new idea for the selection of immunotherapeutic targets and prognostic biomarkers for cervical cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02101-9.

NSC348884 cytotoxicity is not mediated by inhibition of nucleophosmin oligomerization

Nucleophosmin (NPM) mutations causing its export from the nucleoli to the cytoplasm are frequent in acute myeloid leukemia (AML). Due to heterooligomerization of wild type NPM with the AML-related mutant, the wild-type becomes misplaced from the nucleoli and its functions are significantly altered. Dissociation of NPM heterooligomers may thus restore the proper localization and function of wild-type NPM. NSC348884 is supposed to act as a potent inhibitor of NPM oligomerization. The effect of NSC348884 on the NPM oligomerization was thoroughly examined by fluorescence lifetime imaging with utilization of FRET and by a set of immunoprecipitation and electrophoretic methods. Leukemia-derived cell lines and primary AML cells as well as cells transfected with fluorescently labeled NPM forms were investigated. Our results clearly demonstrate that NSC348884 does not inhibit formation of NPM oligomers neither in vivo nor in vitro. Instead, we document that NSC348884 cytotoxicity is rather associated with modified cell adhesion signaling. The cytotoxic mechanism of NSC348884 has therefore to be reconsidered.

Systemic analysis of the expression and prognostic significance of PAKs in breast cancer

PAKs (p21-activated kinases) are reported to play crucial roles in a variety of cellular processes and participate in the progression of human cancers. However, the expression and prognostic values of PAKs remain poorly explored in breast cancers. In our study, we examined the mRNA and protein expression levels of PAKs and the prognostic value. We also analyzed the interaction network, genetic alteration, and functional enrichment of PAKs. The results showed that the mRNA levels of PAK1, PAK2, PAK4 and PAK6 were significantly up-regulated in breast cancer compared with normal tissues, while the reverse trend for PAK3 and PAK5 was found, furthermore, the proteins expression of PAK1, PAK2 and PAK4 in breast cancer tissues were higher than that in normal breast tissues. Survival analysis revealed breast cancer patients with low mRNA expression of PAK3 and PAK5 showed worse RFS, conversely, elevated PAK4 levels predicted worse RFS. In addition, the breast cancer patients with PAKs genetic alterations correlated with worse OS. These results indicated that PAKs might be promising potential biomarkers for breast cancer.

High prevalence of pulmonary findings in computed tomographies of HTLV-1-infected patients with and without adult-T cell leukemia/lymphoma - implications for staging

Lung involvement has been reported in HTLV-1 carriers and in patients with ATLL. Whether there are differences in the pattern of lung involvement between ATLL and HTLV carriers in North American patients is unknown. We aimed to compare CT pulmonary findings among patients with HTLV-1 infection with and without ATLL. Among 140 patients with HTLV-1 diagnosis, 97 had CT chest available. Of these, 72 (74.2%) had ATLL and 25 (25.8%) did not have ATLL. CT chest abnormalities were present in 90 (92.8%) participants (94.4% in ATLL; 88% in non-ATLL). Higher rates of lymphadenopathy (69.4% versus 24%, p < .01) and lower rates of bronchiectasis (25% versus 48%, p = .04) were seen in ATLL compared to non-ATLL. Our study supports that staging of lung involvement in ATLL should consider HTLV-associated pulmonary findings as not all CT chest abnormalities necessarily represent malignant infiltration.