Focal Adhesion Kinase as a Potential Target in AML and MDS

Stromal bone marrow fibroblasts and mesenchymal stem cells support acute myeloid leukaemia cells and promote therapy resistance

The bone marrow (BM) is the primary site of adult haematopoiesis, where stromal elements (e.g. fibroblasts and mesenchymal stem cells [MSCs]) work in concert to support blood cell development. However, the establishment of an abnormal clone can lead to a blood malignancy, such as acute myeloid leukaemia (AML). Despite our increased understanding of the pathophysiology of the disease, patient survival remains suboptimal, mainly driven by the development of therapy resistance. In this review, we highlight the importance of bone marrow fibroblasts and MSCs in health and acute myeloid leukaemia and their impact on patient prognosis. We discuss how stromal elements reduce the killing effects of therapies via a combination of contact-dependent (e.g. integrins) and contact-independent (i.e. secreted factors) mechanisms, accompanied by the establishment of an immunosuppressive microenvironment. Importantly, we underline the challenges of therapeutically targeting the bone marrow stroma to improve acute myeloid leukaemia patient outcomes, due to the inherent heterogeneity of stromal cell populations. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Integrin signaling is critical for myeloid-mediated support of T-cell acute lymphoblastic leukemia

We previously found that T-cell acute lymphoblastic leukemia (T-ALL) requires support from tumor-associated myeloid cells, which activate Insulin Like Growth Factor 1 Receptor (IGF1R) signaling in leukemic blasts. However, IGF1 is not sufficient to sustain T-ALL in vitro, implicating additional myeloid-mediated signals in leukemia progression. Here, we find that T-ALL cells require close contact with myeloid cells to survive. Transcriptional profiling and in vitro assays demonstrate that integrin-mediated cell adhesion activates downstream focal adhesion kinase (FAK)/ proline-rich tyrosine kinase 2 (PYK2), which are required for myeloid-mediated T-ALL support, partly through activation of IGF1R. Blocking integrin ligands or inhibiting FAK/PYK2 signaling diminishes leukemia burden in multiple organs and confers a survival advantage in a mouse model of T-ALL. Inhibiting integrin-mediated adhesion or FAK/PYK2 also reduces survival of primary patient T-ALL cells co-cultured with myeloid cells. Furthermore, elevated integrin pathway gene signatures correlate with higher FAK signaling and myeloid gene signatures and are associated with an inferior prognosis in pediatric T-ALL patients. Together, these findings demonstrate that integrin activation and downstream FAK/PYK2 signaling are important mechanisms underlying myeloid-mediated support of T-ALL progression.

Focal adhesion kinase activation by calcium-dependent calpain is involved in chronic lymphocytic leukaemia cell aggressiveness

Signalling events downstream the B-cell receptor (BCR) are central for the survival and progression of chronic lymphocytic leukaemia (CLL) cells. Focal adhesion kinase (FAK), regulated through calpain, interacts with molecules of BCR signalling, cytoskeletal modelling and disease progression, such as Src/Lyn, cortactin and HS1. Hypothesizing that FAK might play a key role in CLL pathogenesis, we observed a down-modulation of FAK whole form, associated with FAK cleavage due to calpain activity upon BCR stimulation. Patients, whose cells were able to release Ca++ after BCR stimulation, had less amount of full-length FAK, which translated into a higher presence of cleaved/activated form of the protein phosphorylated at Y397, these features being mostly shown by immunoglobulin heavy chain (IGHV)-unmutated poor-prognosis patients. Moreover, we found that cortactin and HS1 proteins were overexpressed in those cells, suggesting a possible interplay with FAK. Treatment with the FAK inhibitor Defactinib was able to induce apoptosis in CLL cells. In conclusion, the malignant phenotype in unfavourable-prognosis patients seems to be encouraged by the overexpression of cortactin and HS1, that, together with FAK, may be involved in a druggable pathogenetic pathway in CLL.

PYK2 is overexpressed in chronic lymphocytic leukaemia: A potential new therapeutic target

Chronic Lymphocytic Leukaemia (CLL) is the most common adult B-cell leukaemia and despite improvement in patients' outcome, following the use of targeted therapies, it remains incurable. CLL supportive microenvironment plays a key role in both CLL progression and drug resistance through signals that can be sensed by the main components of the focal adhesion complex, such as FAK and PYK2 kinases. Dysregulations of both kinases have been observed in several metastatic cancers, but their role in haematological malignancies is still poorly defined. We characterized FAK and PYK2 expression and observed that PYK2 expression is higher in leukaemic B cells and its overexpression significantly correlates with their malignant transformation. When targeting both FAK and PYK2 with the specific inhibitor defactinib, we observed a dose-response effect on CLL cells viability and survival. In vivo treatment of a CLL mouse model showed a decrease of the leukaemic clone in all the lymphoid organs along with a significant reduction of macrophages and of the spleen weight and size. Our results first define a possible prognostic value for PYK2 in CLL, and show that both FAK and PYK2 might become putative targets for both CLL and its microenvironment (e.g. macrophages), thus paving the way to an innovative therapeutic strategy.

Harnessing the cyclization strategy for new drug discovery

The design of new ligands with high affinity and specificity against the targets of interest has been a central focus in drug discovery. As one of the most commonly used methods in drug discovery, the cyclization represents a feasible strategy to identify new lead compounds by increasing structural novelty, scaffold diversity and complexity. Such strategy could also be potentially used for the follow-on drug discovery without patent infringement. In recent years, the cyclization strategy has witnessed great success in the discovery of new lead compounds against different targets for treating various diseases. Herein, we first briefly summarize the use of the cyclization strategy in the discovery of new small-molecule lead compounds, including the proteolysis targeting chimeras (PROTAC) molecules. Particularly, we focus on four main strategies including fused ring cyclization, chain cyclization, spirocyclization and macrocyclization and highlight the use of the cyclization strategy in lead generation. Finally, the challenges including the synthetic intractability, relatively poor pharmacokinetics (PK) profiles and the absence of the structural information for rational structure-based cyclization are also briefly discussed. We hope this review, not exhaustive, could provide a timely overview on the cyclization strategy for the discovery of new lead compounds.

Netrin-1 induces the anti-apoptotic and pro-survival effects of B-ALL cells through the Unc5b-MAPK axis

BACKGROUND

B-cell acute lymphoblastic leukemia (B-ALL) comprises over 85% of all acute lymphoblastic leukemia (ALL) cases and is the most common childhood malignancy. Although the 5 year overall survival of patients with B-ALL exceeds 90%, patients with relapsed or refractory B-ALL may suffer from poor prognosis and adverse events. The axon guidance factor netrin-1 has been reported to be involved in the tumorigenesis of many types of cancers. However, the impact of netrin-1 on B-ALL remains unknown.

METHODS

The expression level of netrin-1 in peripheral blood samples of children with B-ALL and children without neoplasia was measured by enzyme-linked immunosorbent assay (ELISA) kits. Then, CCK-8 cell proliferation assays and flow cytometric analysis were performed to detect the viability and apoptosis of B-ALL cells (Reh and Sup B15) treated with exogenous recombinant netrin-1 at concentrations of 0, 25, 50, and 100 ng/ml. Furthermore, co-immunoprecipitation(co-IP) was performed to detect the receptor of netrin-1. UNC5B expression interference was induced in B-ALL cells with recombinant lentivirus, and then CCK-8 assays, flow cytometry assays and western blotting assays were performed to verify that netrin-1 might act on B-ALL cells via the receptor Unc5b. Finally, western blotting and kinase inhibitor treatment were applied to detect the downstream signaling pathway.

RESULTS

Netrin-1 expression was increased in B-ALL, and netrin-1 expression was upregulated in patients with high- and intermediate-risk stratification group of patients. Then, we found that netrin-1 induced an anti-apoptotic effect in B-ALL cells, implying that netrin-1 plays an oncogenic role in B-ALL. co-IP results showed that netrin-1 interacted with the receptor Unc5b in B-ALL cells. Interference with UNC5B was performed in B-ALL cells and abolished the antiapoptotic effects of netrin-1. Further western blotting was applied to detect the phosphorylation levels of key molecules in common signaling transduction pathways in B-ALL cells treated with recombinant netrin-1, and the FAK-MAPK signaling pathway was found to be activated. The anti-apoptotic effect of netrin-1 and FAK-MAPK phosphorylation was abrogated by UNC5B interference. FAK inhibitor treatment and ERK inhibitor treatment were applied and verified that the FAK-MAPK pathway may be downstream of Unc5b.

CONCLUSION

Taken together, our findings suggested that netrin-1 induced the anti-apoptotic effect of B-ALL cells through activation of the FAK-MAPK signaling pathway by binding to the receptor Unc5b. Video Abstract.

Identification of Thieno[3,2-d]pyrimidine Derivatives as Dual Inhibitors of Focal Adhesion Kinase and FMS-like Tyrosine Kinase 3

Focal adhesion kinase (FAK) is overexpressed in highly invasive and metastatic cancers. To identify novel FAK inhibitors, we designed and synthesized various thieno[3,2-d]pyrimidine derivatives. An intensive structure-activity relationship (SAR) study led to the identification of 26 as a lead. Moreover, 26, a multitargeted kinase inhibitor, possesses excellent potencies against FLT3 mutants as well as FAK. Gratifyingly, 26 remarkably inhibits recalcitrant FLT3 mutants, including F691L, that cause drug resistance. Importantly, 26 is superior to PF-562271 in terms of apoptosis induction, anchorage-independent growth inhibition, and tumor burden reduction in the MDA-MB-231 xenograft mouse model. Also, 26 causes regression of tumor growth in the MV4-11 xenograft mouse model, indicating that it could be effective against acute myeloid leukemia (AML). Finally, in an orthotopic mouse model using MDA-MB-231, 26 remarkably prevents metastasis of orthotopic tumors to lymph nodes. Taken together, the results indicate that 26 possesses potential therapeutic value against highly invasive cancers and relapsed AML.

Novel Polyethylene Glycol-Conjugated Triazole Derivative with High Thyrointegrin αvβ3 Affinity in Acute Myeloid Leukemia Management

(1) Background: Acute myeloid leukemia (AML) accounts for up to one-third of more than 60,000 leukemia cases diagnosed annually in the U.S. Primary AML cells express membrane αvβ3 integrin, which is associated with adverse prognosis and resistance to chemotherapies. A novel anticancer compound Polyethylene glycol-conjugated bi-TriAzole Tetraiodothyroacetic acid (P-bi-TAT) interacts with high affinity (Ki 0.3 nM) and specificity with the thyrointegrin αvβ3. We evaluated P-bi-TAT activities in two different AML models representing monocytic and myelocytic forms of acute leukemia. (2) Methods and Results: The in vivo AML models were established prior to initiation of treatment protocols by grafting human leukemia cells in immunocompromised mice. IVIS imaging scans revealed that leukemic colonies were extensively established throughout the bone marrow, liver, and lung of the untreated animals. In animals treated with P-bi-TAT at daily doses ranging from 1-10 mg/kg, subcutaneously for 2-3 weeks, IVIS imaging scans revealed 95% reduction in bone marrow colonies and leukemic colonies in liver and lung. Also, the leukemic cells were not detected in bone marrow samples of P-bi-TAT-treated animals. The anti-neoplastic effect of P-bi-TAT administration on leukemic cells was associated with marked inhibition of NF-κB activity. We conclude that experimental P-bi-TAT therapy in vivo appears extraordinarily effective against the two forms of human AML models in mice. Because the P-bi-TAT molecular target, thyrointegrin αvβ3, is consistently expressed in many, if not all, clinical AML samples, P-bi-TAT-based therapy seems to have significant clinical potential in treating most AML sub-types. Hence, P-bi-TAT represents a promising targeted therapeutic agent for AML patients.

Effects of jasplakinolide on cytotoxicity, cytoskeleton and apoptosis in two different colon cancer cell lines treated with m-THPC-PDT

Colorectal cancer (CRC) is a common malignant tumor, and metastasis is one of the most important challenges in the treatment of CRC. Photodynamic therapy (PDT) is a novel and non-invasive treatment that influence cytoskeleton and to reduce cancer metastases. In addition, cytoskeleton is related to cancer metastases. Two isogenic colorectal cancer cell lines SW480 and SW620 were used in the present study, we found that m-THPC mediated PDT changed the cytotoxicity, apoptosis and cytoskeleton in both cell lines. Interestingly, the expression of intermediate filaments protein cytokeratin18 were different in the two cell lines. In order to further confirm the relationship between cytoskeleton and cell migration, we combined with microfilament stabilizer jasplakinolide (JASP) to observe the effects of microfilaments on cell migration, cytotoxicity and apoptosis. Taken together, these findings suggest that m-THPC-PDT could induce cytoplasmic cytoskeleton destruction in both types of cells, especially on microfilaments and microtubules. Moreover, in SW480 cells, microtubules may participate in the apoptosis process induced by m-THPC-PDT, while microfilaments may participate in the process of m-THPC-PDT inhibiting cell migration. But in SW620 cells, only microfilaments may be involved in m-THPC-PDT induced apoptosis and inhibition of cell migration.

A clinical transcriptome approach to patient stratification and therapy selection in acute myeloid leukemia

As more clinically-relevant genomic features of myeloid malignancies are revealed, it has become clear that targeted clinical genetic testing is inadequate for risk stratification. Here, we develop and validate a clinical transcriptome-based assay for stratification of acute myeloid leukemia (AML). Comparison of ribonucleic acid sequencing (RNA-Seq) to whole genome and exome sequencing reveals that a standalone RNA-Seq assay offers the greatest diagnostic return, enabling identification of expressed gene fusions, single nucleotide and short insertion/deletion variants, and whole-transcriptome expression information. Expression data from 154 AML patients are used to develop a novel AML prognostic score, which is strongly associated with patient outcomes across 620 patients from three independent cohorts, and 42 patients from a prospective cohort. When combined with molecular risk guidelines, the risk score allows for the re-stratification of 22.1 to 25.3% of AML patients from three independent cohorts into correct risk groups. Within the adverse-risk subgroup, we identify a subset of patients characterized by dysregulated integrin signaling and RUNX1 or TP53 mutation. We show that these patients may benefit from therapy with inhibitors of focal adhesion kinase, encoded by PTK2, demonstrating additional utility of transcriptome-based testing for therapy selection in myeloid malignancy.

Serum levels of FAK and some of its effectors in adult AML: correlation with prognostic factors and survival

Focal adhesion kinase (FAK), human myofibrillogenesis regulator-1 (MR-1), ephrin receptor type A4 (EphA4), proto-oncogene tyrosine kinase Src (Src), and protein kinase C (PKC) are important markers in proliferation, survival, and migration in some cancers. However, the significance of each is still unclear in different malignancies, including acute myeloid leukemia (AML). Therefore, this study was conducted to investigate their serum levels in Egyptian adult de novo AML patients (n = 70) against healthy volunteers (n = 20). We managed to study the correlation between each pair and to investigate their association with diagnosis, prognosis, and survival. Serum levels were analyzed using enzyme-linked immunosorbent assay (ELISA). We found that FAK, MR-1, Src, and PKC serum levels were significantly higher in AML patients compared to control (p < 0.0001), and this was associated with significantly lower EphA4 level (p < 0.0001). Interestingly, we also observed a significant negative correlation of FAK (p = 0.027), MR-1 (p = 0.003), Src (p = 0.038), and PKC (p = 0.03) with patients' overall survival (OS) while there was a positive significant correlation between EphA4 and OS (p = 0.007). In conclusion, this study suggests that FAK, MR-1, EphA4, Src, and PKC may be used as early diagnostic and prognostic markers with high sensitivity and specificity in AML patients and thus may be incorporated into the patients' early diagnostic and prognostic panels.

Targeting MCL-1 dysregulates cell metabolism and leukemia-stroma interactions and resensitizes acute myeloid leukemia to BCL-2 inhibition

MCL-1 and BCL-2 are both frequently overexpressed in acute myeloid leukemia (AML) and critical for the survival of AML cells and AML stem cells. MCL-1 is a key factor in venetoclax resistance. Using genetic and pharmacological approaches, we discovered that MCL-1 regulates leukemia cell bioenergetics and carbohydrate metabolisms, including the TCA cycle, glycolysis and pentose phosphate pathway and modulates cell adhesion proteins and leukemia-stromal interactions. Inhibition of MCL-1 sensitizes to BCL-2 inhibition in AML cells and AML stem/progenitor cells, including those with intrinsic and acquired resistance to venetoclax through cooperative release of pro-apoptotic BIM, BAX, and BAK from binding to anti-apoptotic BCL- 2 proteins and inhibition of cell metabolism and key stromal microenvironmental mechanisms. The combined inhibition of MCL-1 by MCL-1 inhibitor AZD5991 or CDK9 inhibitor AZD4573 and BCL-2 by venetoclax greatly extended survival of mice bearing patient-derived xenografts established from an AML patient who acquired resistance to venetoclax/decitabine. These results demonstrate that co-targeting MCL-1 and BCL-2 improves the efficacy of and overcomes pre-existing and acquired resistance to BCL-2 inhibition. Activation of metabolomic pathways and leukemia-stroma interactions are newly discovered functions of MCL-1 in AML, which are independent from canonical regulation of apoptosis by MCL-1. Our data provide new mechanisms of synergy and a rationale for co-targeting MCL-1 and BCL-2 clinically in patients with AML and potentially other cancers.

NRF2 regulates the sensitivity of human NSCLC cells to cystine deprivation-induced ferroptosis via FOCAD-FAK signaling pathway

Transcription factor nuclear factor-erythroid 2-like 2 (NRF2) mainly regulates cellular antioxidant response, redox homeostasis and metabolic balance. Our previous study illustrated the translational significance of NRF2-mediated transcriptional repression, and the transcription of FOCAD gene might be negatively regulated by NRF2. However, the detailed mechanism and the related significance remain unclear. In this study, we mainly explored the effect of NRF2-FOCAD signaling pathway on ferroptosis regulation in human non-small-cell lung carcinoma (NSCLC) model. Our results confirmed the negative regulation relationship between NRF2 and FOCAD, which was dependent on NRF2-Replication Protein A1 (RPA1)-Antioxidant Response Elements (ARE) complex. In addition, FOCAD promoted the activity of focal adhesion kinase (FAK), which further enhanced the sensitivity of NSCLC cells to cysteine deprivation-induced ferroptosis via promoting the tricarboxylic acid (TCA) cycle and the activity of Complex I in mitochondrial electron transport chain (ETC). However, FOCAD didn't affect GPX4 inhibition-induced ferroptosis. Moreover, the treatment with the combination of NRF2 inhibitor (brusatol) and erastin showed better therapeutic action against NSCLC in vitro and in vivo than single treatment, and the improved therapeutic function partially depended on the activation of FOCAD-FAK signal. Taken together, our study indicates the close association of NRF2-FOCAD-FAK signaling pathway with cysteine deprivation-induced ferroptosis, and elucidates a novel insight into the ferroptosis-based therapeutic approach for the patients with NSCLC.

"Caught in the net": the extracellular matrix of the bone marrow in normal hematopoiesis and leukemia

The influence of the bone marrow microenvironment on normal hematopoiesis, but also leukemia, has largely been accepted. However, the focus has been predominantly on the role of various cell types or cytokines maintaining hematopoietic stem cells or protecting leukemia stem cells from different therapies. A frequently overlooked component of the bone marrow microenvironment is the extracellular matrix, which not only provides a mechanical scaffold, but also serves as a source of growth factors. We discuss here how extracellular matrix proteins directly or indirectly modulate hematopoietic stem cell physiology and influence leukemia progression. It is hoped that existing and future studies on this topic may propel forward the possibility of augmenting normal hematopoiesis and improving therapies for leukemia, for instance, by targeting of the extracellular matrix in the bone marrow.

Combinatorial Inhibition of Focal Adhesion Kinase and BCL-2 Enhances Antileukemia Activity of Venetoclax in Acute Myeloid Leukemia

Focal adhesion kinase (FAK) promotes cancer cell growth and metastasis. We previously reported that FAK inhibition by the selective inhibitor VS-4718 exerted antileukemia activities in acute myeloid leukemia (AML). The mechanisms involved, and whether VS-4718 potentiates efficacy of other therapeutic agents, have not been investigated. Resistance to apoptosis inducted by the BCL-2 inhibitor ABT-199 (venetoclax) in AML is mediated by preexisting and ABT-199-induced overexpression of MCL-1 and BCL-XL. We observed that VS-4718 or silencing FAK with siRNA decreased MCL-1 and BCL-XL levels. Importantly, VS-4718 antagonized ABT-199-induced MCL-1 and BCL-XL. VS-4718 markedly synergized with ABT-199 to induce apoptosis in AML cells, including primary AML CD34+ cells and AML cells overexpressing MCL-1 or BCL-XL. In a patient-derived xenograft (PDX) model derived from a patient sample with NPM1/FLT3-ITD/TET2/DNMT3A/WT1 mutations and complex karyotype, VS-4718 statistically significantly reduced leukemia tissue infiltration and extended survival (72 vs. control 36 days, P = 0.0002), and only its combination with ABT-199 effectively decreased systemic leukemia tissue infiltration and circulating blasts, and prolonged survival (65.5 vs. control 36 days, P = 0.0119). Furthermore, the combination decreased NFκB signaling and induced the expression of IFN genes in vivo The combination also markedly extended survival of a second PDX model developed from an aggressive, TP53-mutated complex karyotype AML sample. The data suggest that the combined inhibition of FAK and BCL-2 enhances antileukemia activity in AML at least in part by suppressing MCL-1 and BCL-XL and that this combination may be effective in AML with TP53 and other mutations, and thus benefit patients with high-risk AML.

Mesenchymal Stem Cells in Aplastic Anemia and Myelodysplastic Syndromes: The "Seed and Soil" Crosstalk

There is growing interest in the contribution of the marrow niche to the pathogenesis of bone marrow failure syndromes, i.e., aplastic anemia (AA) and myelodysplastic syndromes (MDSs). In particular, mesenchymal stem cells (MSCs) are multipotent cells that contribute to the organization and function of the hematopoietic niche through their repopulating and supporting abilities, as well as immunomodulatory properties. The latter are of great interest in MDSs and, particularly, AA, where an immune attack against hematopoietic stem cells is the key pathogenic player. We, therefore, conducted Medline research, including all available evidence from the last 10 years concerning the role of MSCs in these two diseases. The data presented show that MSCs display morphologic, functional, and genetic alterations in AA and MDSs and contribute to immune imbalance, ineffective hematopoiesis, and leukemic evolution. Importantly, adoptive MSC infusion from healthy donors can be exploited to heal the "sick" niche, with even better outcomes if cotransplanted with allogeneic hematopoietic stem cells. Finally, future studies on MSCs and the whole microenvironment will further elucidate AA and MDS pathogenesis and possibly improve treatment.

LGALS1 acts as a pro-survival molecule in AML

The galectin LGALS1 is a glycan binding protein that regulates intracellular (e.g. signal transduction) and extracellular processes (e.g. immunity, leukocyte mobilization) that support cell survival. The protein is best known for its role in RAS signaling. LGALS1 is important in acute lymphoblastic leukemia but its role in acute myeloid leukemia is not well defined. We previously found suppression of LGALS1 in AML cell lines OCI-AML3 and THP-1 sensitized both cell lines to BCL2 inhibitor ABT-737. In this study, we used an in vivo murine OCI-AML3 xenograft model to test whether reduction expression of LGALS1 affects survival. Mice bearing the OCI-AML3 cells with LGALS1 shRNA survived significantly longer than mice with control OCI-AML3 cells. Gene expression profiling using RNASeq was performed using the control and LGALS1 shRNA of p53 WT OCI-AML3 and p53 mutant THP-1 cells. The data reveal distinct differences between the two cell lines in number of genes affected, in pathways associated with these genes, in expression of oncogenes, and in the transcription factors involved. The p53 pathway is prominent in OCI-AML3 cells. An examination of LGALS1 mRNA in an AML patient population reveals elevated LGALS1 mRNA is associated with shorter disease free survival and increased blasts in the BM. This data with the xenograft model data presented suggest LGALS1 may be important in the AML microenvironment. In summary, the data presented here suggest that a strategy targeting LGALS1 may benefit AML patients.

Discovery of CDK5 Inhibitors through Structure-Guided Approach

Specific abrogation of cyclin-dependent kinase 5 (CDK5) activity has been validated as a viable approach for the development of anticancer agents. However, no selective CDK5 inhibitor has been reported to date. Herein, a structure-based in silico screening was employed to identify novel scaffolds from a library of compounds to identify potential CDK5 inhibitors that would be relevant for drug discovery. Hits, representatives of three chemical classes, were identified as inhibitors of CDK5. Structural modification of hit-1 resulted in 29 and 30. Compound 29 is a dual inhibitor of CDK5 and CDK2, whereas 30 preferentially inhibits CDK5. Both leads exhibited anticancer activity against acute myeloid leukemia (AML) cells via a mechanism consistent with targeting cellular CDK5. This study provides an effective strategy for discovery of CDK5 inhibitors as potential antileukemic agents.

Inhibition of FAK Signaling Elicits Lamin A/C-Associated Nuclear Deformity and Cellular Senescence

Focal adhesion kinase (FAK) is a non-receptor kinase that facilitates tumor aggressiveness. The effects of FAK inhibition include arresting proliferation, limiting metastasis, and inhibiting angiogenesis. PF-573228 is an ATP-competitive inhibitor of FAK. Treating lung cancer cells with PF-573228 resulted in FAK inactivation and changes in the expressions of lamin A/C and nuclear deformity. Since lamin A/C downregulation or deficiency was associated with cellular senescence, the senescence-associated β-galactosidase (SA-β-gal) assay was used to investigate whether PF-573228 treatment drove cellular senescence, which showed more SA-β-gal-positive cells in culture. p53 is known to play a pivotal role in mediating the progression of cellular senescence, and the PF-573228-treated lung cancer cells resulted in a higher p53 expression level. Subsequently, the FAK depletion in lung cancer cells was employed to confirm the role of FAK inhibition on cellular senescence. FAK depletion and pharmacological inhibition of lung cancer cells elicited similar patterns of cellular senescence, lamin A/C downregulation, and p53 upregulation, implying that FAK signaling is associated with the expression of p53 and the maintenance of lamin A/C levels to shape regular nuclear morphology and manage anti-senescence. Conversely, FAK inactivation led to p53 upregulation, disorganization of the nuclear matrix, and consequently cellular senescence. Our data suggest a new FAK signaling pathway, in that abolishing FAK signaling can activate the senescence program in cells. Triggering cellular senescence could be a new therapeutic approach to limit tumor growth.

Focal Adhesion Genes Refine the Intermediate-Risk Cytogenetic Classification of Acute Myeloid Leukemia

In recent years, several attempts have been made to identify novel prognostic markers in patients with intermediate-risk acute myeloid leukemia (IR-AML), to implement risk-adapted strategies. The non-receptor tyrosine kinases are proteins involved in regulation of cell growth, adhesion, migration and apoptosis. They associate with metastatic dissemination in solid tumors and poor prognosis. However, their role in haematological malignancies has been scarcely studied. We hypothesized that PTK2/FAK, PTK2B/PYK2, LYN or SRC could be new prognostic markers in IR-AML. We assessed PTK2, PTK2B, LYN and SRC gene expression in a cohort of 324 patients, adults up to the age of 70, classified in the IR-AML cytogenetic group. Univariate and multivariate analyses showed that PTK2B, LYN and PTK2 gene expression are independent prognostic factors in IR-AML patients. PTK2B and LYN identify a patient subgroup with good prognosis within the cohort with non-favorable FLT3/NPM1 combined mutations. In contrast, PTK2 identifies a patient subgroup with poor prognosis within the worst prognosis cohort who display non-favorable FLT3/NPM1 combined mutations and underexpression of PTK2B or LYN. The combined use of these markers can refine the highly heterogeneous intermediate-risk subgroup of AML patients, and allow the development of risk-adapted post-remission chemotherapy protocols to improve their response to treatment.

ST8SIA1 Regulates Tumor Growth and Metastasis in TNBC by Activating the FAK-AKT-mTOR Signaling Pathway

Breast cancer stem-like cells (BCSC) are implicated in cancer recurrence and metastasis of triple-negative breast cancer (TNBC). We have recently discovered that ganglioside GD2 expression defines BCSCs and that ST8SIA1 regulates GD2 expression and BCSC function. In this report, we show that ST8SIA1 is highly expressed in primary TNBC; its expression is positively correlated with the expression of several BCSC-associated genes such as BCL11A, FOXC1, CXCR4, PDGFRβ, SOX2, and mutations in p53. CRISPR knockout of ST8SIA1 completely inhibited BCSC functions, including in vitro tumorigenesis and mammosphere formation. Mechanistic studies discovered activation of the FAK-AKT-mTOR signaling pathway in GD2⁺ BCSCs, and its tight regulation by ST8SIA1. Finally, knockout of ST8SIA1 completely blocked in vivo tumor growth and metastasis by TNBC cells. In summary, these data demonstrate the mechanism by which ST8SIA1 regulates tumor growth and metastasis in TNBC and identifies it as a novel therapeutic target.

LncRNAs regulate the cytoskeleton and related Rho/ROCK signaling in cancer metastasis

Some of the key steps in cancer metastasis are the migration and invasion of tumor cells; these processes require rearrangement of the cytoskeleton. Actin filaments, microtubules, and intermediate filaments involved in the formation of cytoskeletal structures, such as stress fibers and pseudopodia, promote the invasion and metastasis of tumor cells. Therefore, it is important to explore the mechanisms underlying cytoskeletal regulation. The ras homolog family (Rho) and Rho-associated coiled-coil containing protein serine/threonine kinase (ROCK) signaling pathway is involved in the regulation of the cytoskeleton. Moreover, long noncoding RNAs (lncRNAs) have essential roles in tumor migration and guide gene regulation during cancer progression. LncRNAs can regulate the cytoskeleton directly or may influence the cytoskeleton via Rho/ROCK signaling during tumor migration. In this review, we focus on the regulatory association between lncRNAs and the cytoskeleton and discuss the pathways and mechanisms involved in the regulation of cancer metastasis.

Identification of a robust subpathway-based signature for acute myeloid leukemia prognosis using an miRNA integrated strategy

Acute myeloid leukemia (AML) is a heterogeneous disease, and survival signatures are urgently needed to better monitor treatment. MiRNAs displayed vital regulatory roles on target genes, which was necessary involved in the complex disease. We therefore examined the expression levels of miRNAs and genes to identify robust signatures for survival benefit analyses. First, we reconstructed subpathway graphs by embedding miRNA components that were derived from low-throughput miRNA-gene interactions. Then, we randomly divided the data sets from The Cancer Genome Atlas (TCGA) into training and testing sets, and further formed 100 subsets based on the training set. Using each subset, we identified survival-related miRNAs and genes, and identified survival subpathways based on the reconstructed subpathway graphs. After statistical analyses of these survival subpathways, the most robust subpathways with the top three ranks were identified, and risk scores were calculated based on these robust subpathways for AML patient prognoses. Among these robust subpathways, three representative subpathways, path: 05200_10 from Pathways in cancer, path: 04110_20 from Cell cycle, and path: 04510_8 from Focal adhesion, were significantly associated with patient survival in the TCGA training and testing sets based on subpathway risk scores. In conclusion, we performed integrated analyses of miRNAs and genes to identify robust prognostic subpathways, and calculated subpathway risk scores to characterize AML patient survival.

Role of Non Receptor Tyrosine Kinases in Hematological Malignances and its Targeting by Natural Products

Tyrosine kinases belong to a family of enzymes that mediate the movement of the phosphate group to tyrosine residues of target protein, thus transmitting signals from the cell surface to cytoplasmic proteins and the nucleus to regulate physiological processes. Non-receptor tyrosine kinases (NRTK) are a sub-group of tyrosine kinases, which can relay intracellular signals originating from extracellular receptor. NRTKs can regulate a huge array of cellular functions such as cell survival, division/propagation and adhesion, gene expression, immune response, etc. NRTKs exhibit considerable variability in their structural make up, having a shared kinase domain and commonly possessing many other domains such as SH2, SH3 which are protein-protein interacting domains. Recent studies show that NRTKs are mutated in several hematological malignancies, including lymphomas, leukemias and myelomas, leading to aberrant activation. It can be due to point mutations which are intragenic changes or by fusion of genes leading to chromosome translocation. Mutations that lead to constitutive kinase activity result in the formation of oncogenes, such as Abl, Fes, Src, etc. Therefore, specific kinase inhibitors have been sought after to target mutated kinases. A number of compounds have since been discovered, which have shown to inhibit the activity of NRTKs, which are remarkably well tolerated. This review covers the role of various NRTKs in the development of hematological cancers, including their deregulation, genetic alterations, aberrant activation and associated mutations. In addition, it also looks at the recent advances in the development of novel natural compounds that can target NRTKs and perhaps in combination with other forms of therapy can show great promise for the treatment of hematological malignancies.

The Possible Importance of β3 Integrins for Leukemogenesis and Chemoresistance in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive bone marrow malignancy where the immature leukemia cells communicate with neighboring cells through constitutive cytokine release and through their cell surface adhesion molecules. The primary AML cells express various integrins. These heterodimeric molecules containing an α and a β chain are cell surface molecules that bind extracellular matrix molecules, cell surface molecules and soluble mediators. The β3 integrin (ITGB3) chain can form heterodimers only with the two α chains αIIb and αV. These integrins are among the most promiscuous and bind to a large number of ligands, including extracellular matrix molecules, cell surface molecules and soluble mediators. Recent studies suggest that the two β3 integrins are important for leukemogenesis and chemosensitivity in human AML. Firstly, αIIb and β3 are both important for adhesion of AML cells to vitronectin and fibronectin. Secondly, β3 is important for the development of murine AML and also for the homing and maintenance of the proliferation for xenografted primary human AML cells, and for maintaining a stem cell transcriptional program. These last effects seem to be mediated through Syk kinase. The β3 expression seems to be regulated by HomeboxA9 (HoxA9) and HoxA10, and the increased β3 expression then activates spleen tyrosine kinase (Syk) and thereby contributes to cytokine hypersensitivity and activation of β2 integrins. Finally, high integrin αV/β3 expression is associated with an adverse prognosis in AML and decreased sensitivity to the kinase inhibitor sorafenib; this integrin can also be essential for osteopontin-induced sorafenib resistance in AML. In the present article, we review the experimental and clinical evidence for a role of β3 integrins for leukemogenesis and chemosensitivity in AML.

Impaired Expression of Focal Adhesion Kinase in Mesenchymal Stromal Cells from Low-Risk Myelodysplastic Syndrome Patients

The pathogenic role of mesenchymal stromal cells (MSCs) in myelodysplastic syndromes (MDS) development and progression has been investigated by numerous studies, yet, it remains controversial in some aspects (1, 2). In the present study, we found distinct features of MSCs from low-risk (LR)-MDS stromal microenvironment as compared to those from healthy subjects. At the molecular level, focal adhesion kinase, a key tyrosine kinase in control of cell proliferation, survival, and adhesion process, was found profoundly suppressed in expression and activation in LR-MDS MSC. At a functional level, LR-MDS MSCs showed impaired growth and clonogenic capacity, which were independent of cellular senescence and apoptosis. The pro-adipogenic differentiation and attenuated osteogenic capacity along with reduced SDF-1 expression could be involved in creating an unfavorable microenvironment for hematopoiesis. In conclusion, our experiments support the theory that the stromal microenvironment is fundamentally altered in LR-MDS, and these preliminary data offer a new perspective on LR-MDS pathophysiology.