Lapatinib induces p27(Kip1)-dependent G₁ arrest through both transcriptional and post-translational mechanisms

Mirk/Dyrk1B Kinase Inhibitors in Targeted Cancer Therapy

During the last years, there has been an increased effort in the discovery of selective and potent kinase inhibitors for targeted cancer therapy. Kinase inhibitors exhibit less toxicity compared to conventional chemotherapy, and several have entered the market. Mirk/Dyrk1B kinase is a promising pharmacological target in cancer since it is overexpressed in many tumors, and its overexpression is correlated with patients' poor prognosis. Mirk/Dyrk1B acts as a negative cell cycle regulator, maintaining the survival of quiescent cancer cells and conferring their resistance to chemotherapies. Many studies have demonstrated the valuable therapeutic effect of Mirk/Dyrk1B inhibitors in cancer cell lines, mouse xenografts, and patient-derived 3D-organoids, providing a perspective for entering clinical trials. Since the majority of Mirk/Dyrk1B inhibitors target the highly conserved ATP-binding site, they exhibit off-target effects with other kinases, especially with the highly similar Dyrk1A. In this review, apart from summarizing the data establishing Dyrk1B as a therapeutic target in cancer, we highlight the most potent Mirk/Dyrk1B inhibitors recently reported. We also discuss the limitations and perspectives for the structure-based design of Mirk/Dyrk1B potent and highly selective inhibitors based on the accumulated structural data of Dyrk1A and the recent crystal structure of Dyrk1B with AZ191 inhibitor.

Human Blood Serum Counteracts EGFR/HER2-Targeted Drug Lapatinib Impact on Squamous Carcinoma SK-BR-3 Cell Growth and Gene Expression

Lapatinib is a targeted therapeutic inhibiting HER2 and EGFR proteins. It is used for the therapy of HER2-positive breast cancer, although not all the patients respond to it. Using human blood serum samples from 14 female donors (separately taken or combined), we found that human blood serum dramatically abolishes the lapatinib-mediated inhibition of growth of the human breast squamous carcinoma SK-BR-3 cell line. This antagonism between lapatinib and human serum was associated with cancelation of the drug induced G1/S cell cycle transition arrest. RNA sequencing revealed 308 differentially expressed genes in the presence of lapatinib. Remarkably, when combined with lapatinib, human blood serum showed the capacity of restoring both the rate of cell growth, and the expression of 96.1% of the genes expression of which were altered by the lapatinib treatment alone. Co-administration of EGF with lapatinib also restores the cell growth and cancels alteration of expression of 95.8% of the genes specific to lapatinib treatment of SK-BR-3 cells. Differential gene expression analysis also showed that in the presence of human serum or EGF, lapatinib was unable to inhibit the Toll-Like Receptor signaling pathway and alter expression of genes linked to the Gene Ontology term of Focal adhesion.

Quiescent Cancer Cells-A Potential Therapeutic Target to Overcome Tumor Resistance and Relapse

Quiescent cancer cells (QCCs) are nonproliferating cells arrested in the G0 phase, characterized by ki67^low and p27^high. QCCs avoid most chemotherapies, and some treatments could further lead to a higher proportion of QCCs in tumors. QCCs are also associated with cancer recurrence since they can re-enter a proliferative state when conditions are favorable. As QCCs lead to drug resistance and tumor recurrence, there is a great need to understand the characteristics of QCCs, decipher the mechanisms that regulate the proliferative-quiescent transition in cancer cells, and develop new strategies to eliminate QCCs residing in solid tumors. In this review, we discussed the mechanisms of QCC-induced drug resistance and tumor recurrence. We also discussed therapeutic strategies to overcome resistance and relapse by targeting QCCs, including (i) identifying reactive quiescent cancer cells and removing them via cell-cycle-dependent anticancer reagents; (ii) modulating the quiescence-to-proliferation switch; and (iii) eliminating QCCs by targeting their unique features. It is believed that the simultaneous co-targeting of proliferating and quiescent cancer cells may ultimately lead to the development of more effective therapeutic strategies for the treatment of solid tumors.

A lineage tree-based hidden Markov model quantifies cellular heterogeneity and plasticity

Individual cells can assume a variety of molecular and phenotypic states and recent studies indicate that cells can rapidly adapt in response to therapeutic stress. Such phenotypic plasticity may confer resistance, but also presents opportunities to identify molecular programs that could be targeted for therapeutic benefit. Approaches to quantify tumor-drug responses typically focus on snapshot, population-level measurements. While informative, these methods lack lineage and temporal information, which are particularly critical for understanding dynamic processes such as cell state switching. As new technologies have become available to measure lineage relationships, modeling approaches will be needed to identify the forms of cell-to-cell heterogeneity present in these data. Here we apply a lineage tree-based adaptation of a hidden Markov model that employs single cell lineages as input to learn the characteristic patterns of phenotypic heterogeneity and state transitions. In benchmarking studies, we demonstrated that the model successfully classifies cells within experimentally-tractable dataset sizes. As an application, we analyzed experimental measurements in cancer and non-cancer cell populations under various treatments. We find evidence of multiple phenotypically distinct states, with considerable heterogeneity and unique drug responses. In total, this framework allows for the flexible modeling of single cell heterogeneity across lineages to quantify, understand, and control cell state switching.

Drug-resistant HER2-positive breast cancer: Molecular mechanisms and overcoming strategies

Breast cancer is one of the most common malignancies and the leading cause of cancer-related death in women. HER2 overexpression is a factor for poor prognosis in breast cancer, and anti-HER2 therapy improves survival in these patients. A dual-targeted combination of pertuzumab and trastuzumab, alongside cytotoxic chemotherapy, constitutes the primary treatment option for individuals with early-stage, HER2-positive breast cancer. Antibody-drug conjugate (ADC) and tyrosine kinase inhibitors (TKI) also increase the prognosis for patients with metastatic breast cancer. However, resistance to targeted therapy eventually occurs. Therefore, it is critical to investigate how HER2-positive breast cancer is resistant to targeted therapy and to develop novel drugs or strategies to overcome the resistance simultaneously. This review aims to provide a comprehensive discussion of the HER2-targeted agents currently in clinical practice, the molecular mechanisms of resistance to these drugs, and the potential strategies for overcoming resistance.

MiR-221 confers lapatinib resistance by negatively regulating p27kip1 in HER2-positive breast cancer

Development of acquired resistance to lapatinib, a dual epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) tyrosine kinase inhibitor, severely limits the duration of clinical response in advanced HER2‐driven breast cancer patients. Although the compensatory activation of the PI3K/Akt survival signal has been proposed to cause acquired lapatinib resistance, comprehensive molecular mechanisms remain required to develop more efficient strategies to circumvent this therapeutic difficulty. In this study, we found that suppression of HER2 by lapatinib still led to Akt inactivation and elevation of FOX3a protein levels, but failed to induce the expression of their downstream pro‐apoptotic effector p27^kip1, a cyclin‐dependent kinase inhibitor. Elevation of miR‐221 was found to contribute to the development of acquired lapatinib resistance by targeting p27^kip1 expression. Furthermore, upregulation of miR‐221 was mediated by the lapatinib‐induced Src family tyrosine kinase and subsequent NF‐κB activation. The reversal of miR‐221 upregulation and p27^kip1 downregulation by a Src inhibitor, dasatinib, can overcome lapatinib resistance. Our study not only identified miRNA‐221 as a pivotal factor conferring the acquired resistance of HER2‐positive breast cancer cells to lapatinib through negatively regulating p27^kip1 expression, but also suggested Src inhibition as a potential strategy to overcome lapatinib resistance.

Arctigenin-mediated cell death of SK-BR-3 cells is caused by HER2 inhibition and autophagy-linked apoptosis

BACKGROUND

Human epidermal growth factor receptor 2 (HER2) is well-known as the therapeutic marker in breast cancer. Therefore, we evaluated anti-cancer activity of arctigenin (ATG) on in SK-BR-3 HER2-overexpressing human breast cancer cells.

METHODS

Cell viability and cytotoxicity were analyzed with MTT and colony-forming assay and cell cycle analysis was performed by flow cytometry. The expression and/or phosphorylation of proteins in whole cell lysate and mitochondrial fraction were analyzed by Western blotting. Cellular levels of LC3 and sequestosome 1 (SQSTM1/P62) were observed by immunofluorescence analysis.

RESULTS

The result showed that ATG decreased cell viability of SK-BR-3 cells in a concentration-dependent manner. Moreover, ATG increased the sub G1 population linked to the suppression of HER2/EGFR1 signaling pathway. Furthermore, ATG increased the phosphorylation of H2AX and down-regulated RAD51 and survivin expressions, indicating that ATG induced DNA damage and inhibited the DNA repair system. We also found that cleavages of caspase-7 and PARP by releasing mitochondrial cytochrome c into the cytoplasm were induced by ATG treatment for 72 h through the reduction of Bcl-2 and Bcl-xL levels in mitochondria. In contrast, the levels of LC-3 and SQSTM1/P62 were increased by ATG for 24 h through the Akt/mTOR and AMPK signaling pathway.

CONCLUSIONS

Taken together, this study indicates that autophagy-linked apoptosis is responsible for the anti-cancer activity of ATG in SK-BR-3 cells, and suggests that ATG is considered a potential therapeutic for the treatment of HER2-overexpressing breast cancer.

Minibrain-related kinase/dual-specificity tyrosine-regulated kinase 1B implication in stem/cancer stem cells biology

Dual-specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B), also known as minibrain-related kinase (MIRK) is one of the best functionally studied members of the DYRK kinase family. DYRKs comprise a family of protein kinases that are emerging modulators of signal transduction pathways, cell proliferation and differentiation, survival, and cell motility. DYRKs were found to participate in several signaling pathways critical for development and cell homeostasis. In this review, we focus on the DYRK1B protein kinase from a functional point of view concerning the signaling pathways through which DYRK1B exerts its cell type-dependent function in a positive or negative manner, in development and human diseases. In particular, we focus on the physiological role of DYRK1B in behavior of stem cells in myogenesis, adipogenesis, spermatogenesis and neurogenesis, as well as in its pathological implication in cancer and metabolic syndrome. Thus, understanding of the molecular mechanisms that regulate signaling pathways is of high importance. Recent studies have identified a close regulatory connection between DYRK1B and the hedgehog (HH) signaling pathway. Here, we aim to bring together what is known about the functional integration and cross-talk between DYRK1B and several signaling pathways, such as HH, RAS and PI3K/mTOR/AKT, as well as how this might affect cellular and molecular processes in development, physiology, and pathology. Thus, this review summarizes the major known functions of DYRK1B kinase, as well as the mechanisms by which DYRK1B exerts its functions in development and human diseases focusing on the homeostasis of stem and cancer stem cells.

HER2 Kinase-Targeted Breast Cancer Therapy: Design, Synthesis, and In Vitro and In Vivo Evaluation of Novel Lapatinib Congeners as Selective and Potent HER2 Inhibitors with Favorable Metabolic Stability

HER2 kinase as a well-established target for breast cancer (BC) therapy is associated with aggressive clinical outcomes; thus, herein we present structural optimization for HER2-selective targeting. HER2 profiling of the developed derivatives demonstrated potent and selective inhibitions (IC₅₀: 5.4-12 nM) compared to lapatinib (IC₅₀: 95.5 nM). Favorably, 17d exhibited minimum off-target kinase activation. NCI-5-dose screening revealed broad-spectrum activities (GI₅₀: 1.43-2.09 μM) and 17d had a remarkable selectivity toward BC. Our compounds revealed significant selective and potent antiproliferative activities (∼20-fold) against HER2+ (AU565, BT474) compared to HER2(-) cells. At 0.1 IC₅₀, 15i, 17d, and 25b inhibited pERK1/2 and pAkt by immunoblotting. Furthermore, 17d demonstrated potent in vivo tumor regression against the BT474 xenograft model. Notably, a metastasis case was observed in the vehicle but not in the test mice groups. CD-1 mice metabolic stability assay revealed high stability and low intrinsic clearance of 17d (T_1/2 > 145 min and CL_int(mic) < 9.6 mL/min/kg).

Self-Assembly of pH-Labile Polymer Nanoparticles for Paclitaxel Prodrug Delivery: Formulation, Characterization, and Evaluation

The efficacy of paclitaxel (PTX) is limited due to its poor solubility, poor bioavailability, and acquired drug resistance mechanisms. Designing paclitaxel prodrugs can improve its anticancer activity and enable formulation of nanoparticles. Overall, the aim of this work is to improve the potency of paclitaxel with prodrug synthesis, nanoparticle formation, and synergistic formulation with lapatinib. Specifically, we improve potency of paclitaxel by conjugating it to α-tocopherol (vitamin E) to produce a hydrophobic prodrug (Pro); this increase in potency is indicated by the 8-fold decrease in half maximal inhibitory concentration (IC50) concentration in ovarian cancer cell line, OVCA-432, used as a model system. The efficacy of the paclitaxel prodrug was further enhanced by encapsulation into pH-labile nanoparticles using Flash NanoPrecipitation (FNP), a rapid, polymer directed self-assembly method. There was an 1100-fold decrease in IC50 concentration upon formulating the prodrug into nanoparticles. Notably, the prodrug formulations were 5-fold more potent than paclitaxel nanoparticles. Finally, the cytotoxic effects were further enhanced by co-encapsulating the prodrug with lapatinib (LAP). Formulating the drug combination resulted in synergistic interactions as indicated by the combination index (CI) of 0.51. Overall, these results demonstrate this prodrug combined with nanoparticle formulation and combination therapy is a promising approach for enhancing paclitaxel potency.

Adipocyte-conditioned medium induces resistance of breast cancer cells to lapatinib

Background

The existence of a cross-talk between peritumoral adipocytes and cancer cells has been increasingly investigated. Several studies have shown that these adipocytes protect tumor cells from the effect of anticancer agents.

Methods

To investigate a potential protective effect of adipocyte-conditioned medium on HER2 positive breast cancer cells exposed to tyrosine kinase inhibitors (TKI) such as lapatinib, we analyzed the sensitivity of HER2 positive breast cancer models in vitro and in vivo on SCID mice in the presence or absence of adipocytes or adipocyte-conditioned medium.

Results

Conditioned medium from differentiated adipocytes reduced the in vitro sensitivity of the HER2+ cell lines BT474 and SKBR3 to TKI. Particularly, conditioned medium abrogated P27 induction in tumor cells by lapatinib but this was observed only when conditioned medium was present during exposure to lapatinib. In addition, resistance was induced with adipocytes derived from murine NIH3T3 or human hMAD cells but not with fibroblasts or preadipocytes. In vivo studies demonstrated that the contact of the tumors with adipose tissue reduced sensitivity to lapatinib. Soluble factors involved in this resistance were found to be thermolabile. Pharmacological modulation of lipolysis in adipocytes during preparation of conditioned media showed that various lipolysis inhibitors abolished the protective effect of conditioned media on tumor cells, suggesting a role for adipocyte lipolysis in the induction of resistance of tumor cells to TKI.

Conclusions

Overall, our results suggest that contact of tumor cells with proximal adipose tissue induces resistance to anti HER2 small molecule inhibitors through the production of soluble thermolabile factors, and that this effect can be abrogated using lipolysis inhibitors.

The DYRK Family of Kinases in Cancer: Molecular Functions and Therapeutic Opportunities

DYRK (dual-specificity tyrosine-regulated kinases) are an evolutionary conserved family of protein kinases with members from yeast to humans. In humans, DYRKs are pleiotropic factors that phosphorylate a broad set of proteins involved in many different cellular processes. These include factors that have been associated with all the hallmarks of cancer, from genomic instability to increased proliferation and resistance, programmed cell death, or signaling pathways whose dysfunction is relevant to tumor onset and progression. In accordance with an involvement of DYRK kinases in the regulation of tumorigenic processes, an increasing number of research studies have been published in recent years showing either alterations of DYRK gene expression in tumor samples and/or providing evidence of DYRK-dependent mechanisms that contribute to tumor initiation and/or progression. In the present article, we will review the current understanding of the role of DYRK family members in cancer initiation and progression, providing an overview of the small molecules that act as DYRK inhibitors and discussing the clinical implications and therapeutic opportunities currently available.

Rapid Self-Assembly of Polymer Nanoparticles for Synergistic Codelivery of Paclitaxel and Lapatinib via Flash NanoPrecipitation

Taxol, a formulation of paclitaxel (PTX), is one of the most widely used anticancer drugs, particularly for treating recurring ovarian carcinomas following surgery. Clinically, PTX is used in combination with other drugs such as lapatinib (LAP) to increase treatment efficacy. Delivering drug combinations with nanoparticles has the potential to improve chemotherapy outcomes. In this study, we use Flash NanoPrecipitation, a rapid, scalable process to encapsulate weakly hydrophobic drugs (logP < 6) PTX and LAP into polymer nanoparticles with a coordination complex of tannic acid and iron formed during the mixing process. We determine the formulation parameters required to achieve uniform nanoparticles and evaluate the drug release in vitro. The size of the resulting nanoparticles was stable at pH 7.4, facilitating sustained drug release via first-order Fickian diffusion. Encapsulating either PTX or LAP into nanoparticles increases drug potency (as indicated by the decrease in IC-50 concentration); we observe a 1500-fold increase in PTX potency and a six-fold increase in LAP potency. When PTX and LAP are co-loaded in the same nanoparticle, they have a synergistic effect that is greater than treating with two single-drug-loaded nanoparticles as the combination index is 0.23 compared to 0.40, respectively.

A phase I study of HER1, HER2 dual kinase inhibitor lapatinib plus the proteasome inhibitor bortezomib in patients with advanced malignancies

PURPOSE

This phase I trial evaluated the maximum tolerated dose, safety and preliminary efficacy of lapatinib, a HER1, HER2 dual kinase inhibitor plus bortezomib, a proteasome inhibitor, in adult patients with advanced malignancies.

METHODS

Patients were enrolled in a standard 3 + 3 design with lapatinib (L) 750, 1000, 1250 or 1500 mg daily, and bortezomib (B) 0.7, 1.0, 1.3 or 1.6 mg/m² for 3 weeks with 1 week off. Dose-limiting toxicities (DLT) were assessed during the first 28 days RESULTS: Fifteen patients received the combination of lapatinib and bortezomib in three different cohorts and ten were evaluable for DLT. There were no DLTs. Anorexia was the most common adverse event. Biomarker analysis showed upregulation of p27 expression with lapatinib and the combination. No tumor response was observed and thus the study was closed early.

CONCLUSION

The combination of lapatinib and bortezomib was well tolerated but no complete or partial tumor responses were observed at the dose levels tested. CLINICALTRIALS.

GOV IDENTIFIER

NCT01497626.

Tomentosin Displays Anti-Carcinogenic Effect in Human Osteosarcoma MG-63 Cells via the Induction of Intracellular Reactive Oxygen Species

Tomentosin is a natural sesquiterpene lactone extracted from various plants and is widely used as a medicine because it exhibits essential therapeutic properties. In this study, we investigated the anti-carcinogenic effects of tomentosin in human osteosarcoma MG-63 cells by performing cell migration/viability/proliferation, apoptosis, and reactive oxygen species (ROS) analysis assays. MG-63 cells were treated with various doses of tomentosin. After treatment with tomentosin, MG-63 cells were analyzed using the MTT assay, colony formation assay, cell counting assay, wound healing assay, Boyden chamber assay, zymography assay, cell cycle analysis, FITC Annexin V apoptosis assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, western blot analysis, and ROS detection analysis. Our results indicated that tomentosin decreased cell viability and migration ability in MG-63 cells. Moreover, tomentosin induced apoptosis, cell cycle arrest, DNA damage, and ROS production in MG-63 cells. Furthermore, tomentosin-induced intracellular ROS decreased cell viability and induced apoptosis, cell cycle arrest, and DNA damage in MG-63 cells. Taken together, our results suggested that tomentosin exerted anti-carcinogenic effects in MG-63 cells by induction of intracellular ROS.

A wake-up call to quiescent cancer cells - potential use of DYRK1B inhibitors in cancer therapy

Nondividing cancer cells are relatively resistant to chemotherapeutic drugs and environmental stress factors. Promoting cell cycle re-entry of quiescent cancer cells is a potential strategy to enhance the cytotoxicity of agents that target cycling cells. It is therefore important to elucidate the mechanisms by which these cells are maintained in the quiescent state. The protein kinase dual specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B) is overexpressed in a subset of cancers and maintains cellular quiescence by counteracting G0 /G1 -S phase transition. Specifically, DYRK1B controls the S phase checkpoint by stabilizing the cyclin-dependent kinase (CDK) inhibitor p27Kip1 and inducing the degradation of cyclin D. DYRK1B also stabilizes the DREAM complex that represses cell cycle gene expression in G0 arrested cells. In addition, DYRK1B enhances cell survival by upregulating antioxidant gene expression and reducing intracellular levels of reactive oxygen species (ROS). Substantial evidence indicates that depletion or inhibition of DYRK1B drives cell cycle re-entry and enhances apoptosis of those quiescent cancer cells with high expression of DYRK1B. Furthermore, small molecule DYRK1B inhibitors sensitize cells to the cytotoxic effects of anticancer drugs that target proliferating cells. These encouraging findings justify continued efforts to investigate the use of DYRK1B inhibitors to disrupt the quiescent state and overturn chemoresistance of noncycling cancer cells.

Foxo-dependent Par-4 Upregulation Prevents Long-term Survival of Residual Cells Following PI3K-Akt Inhibition

Tumor recurrence is a leading cause of death and is thought to arise from a population of residual cells that survive treatment. These residual cancer cells can persist, locally or at distant sites, for years or decades. Therefore, understanding the pathways that regulate residual cancer cell survival may suggest opportunities for targeting these cells to prevent recurrence. Previously, it was observed that the proapoptotic protein (PAWR/Par-4) negatively regulates residual cell survival and recurrence in mice and humans. However, the mechanistic underpinnings on how Par-4 expression is regulated are unclear. Here, it is demonstrated that Par-4 is transcriptionally upregulated following treatment with multiple drugs targeting the PI3K-Akt-mTOR signaling pathway, and identify the Forkhead family of transcription factors as mediators of this upregulation. Mechanistically, Foxo3a directly binds to the Par-4 promoter and activates its transcription following inhibition of the PI3K-Akt pathway. This Foxo-dependent Par-4 upregulation limits the long-term survival of residual cells following treatment with therapeutics that target the PI3K-Akt pathway. Taken together, these results indicate that residual breast cancer tumor cell survival and recurrence requires circumventing Foxo-driven Par-4 upregulation and suggest that approaches to enforce Par-4 expression may prevent residual cell survival and recurrence. Mol Cancer Res; 16(4); 599-609. ©2018 AACR.

Effects of lapatinib on cell proliferation and apoptosis in NB4 cells

Acute promyelocytic leukemia (APL), characterized by the presence of the promyelocytic leukemia (PML)-retinoic acid α receptor (RARα) fusion protein, responds to treatment with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). However, drug resistance and side effects restrict the application of these reagents. Hence, the development of novel therapeutic drugs for APL treatment is critical. Lapatinib, a small-molecule tyrosine kinase inhibitor, has been used in the treatment of different tumors. However, it is unclear whether lapatinib exerts antitumor effects on APL. The present study investigated the antitumor effects and potential mechanisms of lapatinib on NB4 cells derived from APL. Cell Counting Kit-8 assay and colony forming analysis indicated that lapatinib inhibited NB4 cell proliferation in a dose-dependent manner. Flow cytometry analysis revealed that lapatinib induced cell cycle arrest at the S phase and promoted cell apoptosis. Furthermore, Liu's staining and Hoechst 33258 staining revelaed that lapatinib treatment induced an apoptotic nuclear phenomenon. Furthermore, lapatinib induced apoptosis by decreasing Bcl-2 and PML-RARα levels, and by increasing the levels of Bax, cleaved PARP, cleaved caspase-3 and cleaved caspase-9. In addition, lapatinib increased the levels of phospho-p38 MAPK and phospho-JNK, and decreased the levels of phospho-Akt. The p38 inhibitor PD169316 partially blocked lapatinib-induced proliferation inhibition and apoptosis, whereas the JNK inhibitor SP600125 had no such effects. Therefore, treatment with lapatinib may be a promising strategy for APL therapy.

Epidermal Growth Factor Receptor activation promotes ADA3 acetylation through the AKT-p300 pathway

The ADA3 (Alteration/Deficiency in Activation 3) protein is an essential adaptor component of several Lysine Acetyltransferase (KAT) complexes involved in chromatin modifications. Previously, we and others have demonstrated a crucial role of ADA3 in cell cycle progression and in maintenance of genomic stability. Recently, we have shown that acetylation of ADA3 is key to its role in cell cycle progression. Here, we demonstrate that AKT activation downstream of Epidermal Growth Factor Receptor (EGFR) family proteins stimulation leads to phosphorylation of p300, which in turn promotes the acetylation of ADA3. Inhibition of upstream receptor tyrosine kinases (RTKs), HER1 (EGFR)/HER2 by lapatinib and the accompanying reduction of phospho-AKT levels led to a decrease in p300 phosphorylation and ADA3 protein levels. The p300/PCAF inhibitor garcinol also destabilized the ADA3 protein in a proteasome-dependent manner and an ADA3 mutant with K→R mutations exhibited a marked increase in half-life, consistent with opposite role of acetylation and ubiquitination of ADA3 on shared lysine residues. ADA3 knockdown led to cell cycle inhibitory effects, as well as apoptosis similar to those induced by lapatinib treatment of HER2+ breast cancer cells, as seen by accumulation of CDK inhibitor p27, reduction in mitotic marker pH3(S10), and a decrease in the S-phase marker PCNA, as well as the appearance of cleaved PARP. Taken together our results reveal a novel RTK-AKT-p300-ADA3 signaling pathway involved in growth factor-induced cell cycle progression.

Butein inhibits cell proliferation and induces cell cycle arrest in acute lymphoblastic leukemia via FOXO3a/p27kip1 pathway

Acute lymphoblastic leukemia (ALL) is a common hematological malignancy characterized by the uncontrolled proliferation of leukemia cells in children. Discovering and developing effective chemotherapeutic drugs are needed for ALL. In this study, we investigated the anti-leukemic activity of butein and its action mechanisms in ALL. Butein was found to significantly suppress the cellular proliferation of ALL cell lines and primary ALL blasts in a dose-dependent manner. It also induced cell cycle arrest by decreasing the expression of cyclin E and CDK2. We also found that butein promoted nuclear Forkhead Class box O3a (FOXO3a) localization, enhanced the binding of FOXO3a on the p27kip1 gene promoter and then increased the expression of p27kip1. Moreover, we showed that FOXO3a knockdown significantly decreased the proliferation inhibition by butein, whereas overexpression of FOXO3a enhanced the butein-mediated proliferation inhibition. However, overexpression of FOXO3a mutation (C-terminally truncated FOXO3a DNA-binding domain) decreased the proliferation inhibition by butein through decreasing the expression of p27kip1. Our results therefore demonstrate the therapeutic potential of butein for ALL via FOXO3a/p27kip1 pathway.

TXNIP interaction with the Her-1/2 pathway contributes to overall survival in breast cancer

Previous studies have indicated that Her-2 induction causes a strong decrease in thioredoxin interaction protein (TXNIP) in breast cancer cells. However, little is known regarding the prognostic value of TXNIP in clinical breast cancer patients with anti-Her-2 treatment. Using a tissue microarray, we detected TXNIP and p27 expression in breast cancer tissue, as well as corresponding noncancerous tissues. We found that TXNIP expression was associated with better overall survival (OS) in these 150 breast cancer patients and that TXNIP and Her-2 expression status were significantly inversely correlated (r=-0.334, P<0.001). These results were validated in another 101 breast cancer tissue samples (r=-0.422, P<0.001). Moreover, TXNIP expression increased significantly following treatment of the human breast cancer cell lines BT474 and SK-BR-3 with a Her-1/2 inhibitor. Furthermore, TXNIP transfection induced p27 expression and G1 cell cycle arrest and apoptosis. Taken together, our findings suggest that TXNIP plays a critical role in anti-Her-1/Her-2 treatment and may be a potential prognostic marker in breast cancer.

Neuroprotective effects of the anti-cancer drug sunitinib in models of HIV neurotoxicity suggests potential for the treatment of neurodegenerative disorders

BACKGROUND AND PURPOSE

Anti-retrovirals have improved and extended the life expectancy of patients with HIV. However, as this population ages, the prevalence of cognitive changes is increasing. Aberrant activation of kinases, such as receptor tyrosine kinases (RTKs) and cyclin-dependent kinase 5 (CDK5), play a role in the mechanisms of HIV neurotoxicity. Inhibitors of CDK5, such as roscovitine, have neuroprotective effects; however, CNS penetration is low. Interestingly, tyrosine kinase inhibitors (TKIs) display some CDK inhibitory activity and ability to cross the blood-brain barrier.

EXPERIMENTAL APPROACH

We screened a small group of known TKIs for a candidate with additional CDK5 inhibitory activity and tested the efficacy of the candidate in in vitro and in vivo models of HIV-gp120 neurotoxicity.

KEY RESULTS

Among 12 different compounds, sunitinib inhibited CDK5 with an IC50 of 4.2 μM. In silico analysis revealed that, similarly to roscovitine, sunitinib fitted 6 of 10 features of the CDK5 pharmacophore. In a cell-based model, sunitinib reduced CDK5 phosphorylation (pCDK5), calpain-dependent p35/p25 conversion and protected neuronal cells from the toxic effects of gp120. In glial fibrillary acidic protein-gp120 transgenic (tg) mice, sunitinib reduced levels of pCDK5, p35/p25 and phosphorylated tau protein, along with amelioration of the neurodegenerative pathology.

CONCLUSIONS AND IMPLICATIONS

Compounds such as sunitinib with dual kinase inhibitory activity could ameliorate the cognitive impairment associated with chronic HIV infection of the CNS. Moreover, repositioning existing low MW compounds holds promise for the treatment of patients with neurodegenerative disorders.

Nuclear translocation of PKM2 modulates astrocyte proliferation via p27 and -catenin pathway after spinal cord injury

Aberrant functionality of the cell cycle has been implicated in the pathology of traumatic SCI. Although it has been reported that the expressions of various cell cycle related proteins were altered significantly following SCI, detailed information on the subject remains largely unclear. The embryonic pyruvate kinase M2 (PKM2) is an important metabolic kinase in aerobic glycolysis or the warburg effect, however, its functions in central nervous system (CNS) injury remains elusive. Here we demonstrate that PKM2 was not only significantly upregulated by western blot and immunohistochemistry but certain traumatic stimuli also induced translocation of PKM2 into the nucleus in astrocytes following spinal cord injury (SCI). Furthermore, the expression levels and localization of p-β-catenin, p27, cyclin D1 and PCNA were correlated with PKM2 after SCI. In vitro, we also found that PKM2 co-immunoprecipitation with p-β-catenin and p27 respectively. Knockdown of PKM2 apparently decreased the level of PCNA, cyclinD1, p27 in primary astrocyte cells. Taken together, our findings indicate that nuclear translocation of PKM2 promotes astrocytes proliferation after SCI through modulating cell cycle signaling. These discoveries firstly uncovered the role of PKM2 in spinal cord injury and provided a potential therapeutic target for CNS injury and repair.

Mdig, a lung cancer-associated gene, regulates cell cycle progression through p27(KIP1)

Mineral dust-induced gene (mdig) can accelerate cell proliferation. The aim of this study is to investigate the mechanism by which mdig regulates cell proliferation. A549 cells were transfected with siRNA specifically targeting mdig. Cell proliferation and cell cycle progression were measured using MTT assay and cell cycle analysis, respectively. Furthermore, real-time reverse transcription quantitative-polymerase chain reaction (RT-qPCR) was performed in A549 cells transfected with mdig siRNA to examine the expression levels of the cell cycle related genes such as p18(INK4c), p19(INK4d), p21(WAF/CIP1), p27(KIP1), p57(KIP2), cyclin D1, and cyclin E. To further explore the effect of mdig on p27(KIP1), the expression levels of total p27(KIP1) and its subtypes pT187-p27(KIP1) and pS10-p27(KIP1) were assessed by Western blotting. In vivo, Western blotting was performed to check the expression levels of mdig and p27(KIP1) in human lung cancer tissues, para-cancerous normal lung tissues, and para-bronchial stumps. Knockdown of mdig induced increases in p27(KIP1), both on mRNA and protein levels. Furthermore, the phosphorylation of p27(KIP1) at its Thr187 site was also inhibited. Importantly, in lung cancer tissues, upregulation of mdig expression accompanies with the downregulation of p27(KIP1) expression and in bronchial stump, vice versa. The data suggest that mdig-mediated inhibition of p27(KIP1) is important for cell proliferation and tumor formation and reveal therapeutic potential of p27(KIP1) for lung cancer.

Fusarochromanone induces G1 cell cycle arrest and apoptosis in COS7 and HEK293 cells

Fusarochromanone (FC101), a mycotoxin produced by the fungus Fusarium equiseti, is frequently observed in the contaminated grains and feedstuffs, which is toxic to animals and humans. However, the underlying molecular mechanism remains to be defined. In this study, we found that FC101 inhibited cell proliferation and induced cell death in COS7 and HEK293 cells in a concentration-dependent manner. Flow cytometric analysis showed that FC101 induced G₁ cell cycle arrest and apoptosis in the cells. Concurrently, FC101 downregulated protein expression of cyclin D1, cyclin-dependent kinases (CDK4 and CDK6), and Cdc25A, and upregulated expression of the CDK inhibitors (p21^Cip1 and p27^Kip1), resulting in hypophosphorylation of Rb. FC101 also inhibited protein expression of Bcl-2, Bcl-xL, Mcl-1 and survivin, and induced expression of BAD, leading to activation of caspase 3 and cleavage of PARP, indicating caspase-dependent apoptosis. However, Z-VAD-FMK, a pan-caspase inhibitor, only partially prevented FC101-induced cell death, implying that FC101 may induce cell death through both caspase-dependent and -independent mechanisms. Our results support the notion that FC101 executes its toxicity at least by inhibiting cell proliferation and inducing cell death.

Systemic therapy for early-stage HER2-positive breast cancers: time for a less-is-more approach?

Trastuzumab-based chemotherapy has dramatically improved outcomes for patients with all stages of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Additional HER2-directed agents that have recently been approved are also expected to improve outcomes. Patients with small, lymph node-negative, HER2-positive breast cancers who are treated with trastuzumab-based chemotherapy demonstrate especially favorable responses, with 5-year recurrence rates of <5%. In this review, recent data regarding response rates among patients with early-stage HER2-positive breast cancer treated with trastuzumab-based chemotherapy are discussed. This review supports future studies of the possible omission of chemotherapy in a subset of patients with HER2-positive cancers, specifically those that coexpress hormone receptors.

Src and CXCR4 are involved in the invasiveness of breast cancer cells with acquired resistance to lapatinib

Lapatinib is a dual EGFR and ErbB-2 tyrosine kinase inhibitor that has significantly improved the clinical outcome of ErbB-2-overexpressing breast cancer patients. However, patients inexorably develop mechanisms of resistance that limit the efficacy of the drug. In order to identify potential targets for therapeutic intervention in lapatinib-resistant patients, we isolated, from ErbB-2-overexpressing SK-Br-3 breast cancer cells, the SK-Br-3 Lap-R-resistant subclone, which is able to routinely grow in 1 µM lapatinib. Resistant cells have a more aggressive phenotype compared with parental cells, as they show a higher ability to invade through a matrigel-coated membrane. Lapatinib-resistant cells have an increased Src kinase activity and persistent levels of activation of ERK1/2 and AKT compared with parental cells. Treatment with the Src inhibitor saracatinib in combination with lapatinib reduces AKT and ERK1/2 phosphorylation and restores the sensitivity of resistant cells to lapatinib. SK-Br-3 Lap-R cells also show levels of expression of CXCR4 that are higher compared with parental cells and are not affected by Src inhibition. Treatment with saracatinib or a specific CXCR4 antibody reduces the invasive ability of SK-Br-3 Lap-R cells, with the two drugs showing cooperative effects. Finally, blockade of Src signaling significantly increases TRAIL-induced cell death in SK-Br-3 Lap-R cells. Taken together, our results demonstrate that breast cancer cells with acquired resistance to lapatinib have a more aggressive phenotype compared with their parental counterpart, and that Src signaling and CXCR4 play an important role in this phenomenon, thus representing potential targets for therapeutic intervention in lapatinib-resistant breast cancer patients.