p27 and Leukemia: Cell Cycle and Beyond

Structure-Function Analysis of p57KIP2 in the Human Pancreatic Beta Cell Reveals a Bipartite Nuclear Localization Signal

Mutations in CDKN1C, encoding p57KIP2, a canonical cell cycle inhibitor, underlie multiple pediatric endocrine syndromes. Despite this central role in disease, little is known about the structure and function of p57KIP2 in the human pancreatic beta cell. Since p57KIP2 is predominantly nuclear in human beta cells, we hypothesized that disease-causing mutations in its nuclear localization sequence (NLS) may correlate with abnormal phenotypes. We prepared RIP1 insulin promoter-driven adenoviruses encoding deletions of multiple disease-associated but unexplored regions of p57KIP2 and performed a comprehensive structure-function analysis of CDKN1C/p57KIP2. Real-time polymerase chain reaction and immunoblot analyses confirmed p57KIP2 overexpression, construct size, and beta cell specificity. By immunocytochemistry, wild-type (WT) p57KIP2 displayed nuclear localization. In contrast, deletion of a putative NLS at amino acids 278-281 failed to access the nucleus. Unexpectedly, we identified a second downstream NLS at amino acids 312-316. Further analysis showed that each individual NLS is required for nuclear localization, but neither alone is sufficient. In summary, p57KIP2 contains a classical bipartite NLS characterized by 2 clusters of positively charged amino acids separated by a proline-rich linker region. Variants in the sequences encoding these 2 NLS sequences account for functional p57KIP2 loss and beta cell expansion seen in human disease.

Inhibition of Cell Proliferation and Cell Viability by Sinecatechins in Cutaneous SCC Cells Is Related to an Imbalance of ROS and Loss of Mitochondrial Membrane Potential

The term sinecatechins designates an extract containing a high percentage of catechins obtained from green tea, which is commercially registered as Veregen or Polyphenon E (PE) and may be considered for treatment of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis (AK). As shown here, treatment of four cSCC cell lines with 200 µg/mL of PE resulted in strong, dose-dependent decrease in cell proliferation (20–30%) as well as strongly decreased cell viability (4–21% of controls, 48 h). Effects correlated with loss of mitochondrial membrane potential, whereas early apoptosis was less pronounced. At the protein level, some activation of caspase-3 and enhanced expression of the CDK inhibitor p21 were found. Loss of MMP and induced cell death were, however, largely independent of caspases and of the proapoptotic Bcl-2 proteins Bax and Bak, suggesting that sinecatechins induce also non-apoptotic, alternative cell death pathways, in addition to apoptosis. Reactive oxygen species (ROS) were downregulated in response to PE at 4 h, followed by an increase at 24 h. The contributory role of initially reduced ROS was supported by the antioxidant N-acetyl cysteine, which in combination with PE further enhanced the negative effects on cell viability. Thus, sinecatechins inhibited cell proliferation and viability of cSCC cells, which could suggest the use of PE for AK treatment. The mechanisms appear as linked to an imbalance of ROS levels.

Chidamide and venetoclax synergistically exert cytotoxicity on multiple myeloma by upregulating BIM expression

Background

Multiple myeloma (MM) is the second most common hematologic malignancy with almost all patients eventually having relapse or refractory MM (RRMM), thus novel drugs or combination therapies are needed for improved prognosis. Chidamide and venetoclax, which target histone deacetylase and BCL2, respectively, are two promising agents for the treatment of RRMM.

Results

Herein, we found that chidamide and venetoclax synergistically exert an anti-myeloma effect in vitro in human myeloma cell lines (HMCLs) with a combination index (CI) < 1. Moreover, the synergistic anti-myeloma effect of these two drugs was demonstrated in primary MM cells and MM xenograft mice. Mechanistically, co-exposure to chidamide and venetoclax led to cell cycle arrest at G0/G1 and a sharp increase in DNA double-strand breaks. In addition, the combination of chidamide and venetoclax resulted in BCL-X_L downregulation and BIM upregulation, and the latter protein was proved to play a critical role in sensitizing HMCLs to co-treatment.

Conclusion

In conclusion, these results proved the high therapeutic potential of venetoclax and chidamide combination in curing MM, representing a potent and alternative salvage therapy for the treatment of RRMM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01306-7.

Inhibition of Skp2 enhances doxorubicin-induced cell death in B cell precursor acute lymphoblastic leukemia

S-phase kinase-associated protein 2 (Skp2) is a well-defined component of the Skp2-Culin1-F-box (SCF) E3 ubiquitin ligase complex, which is involved in cell cycle progression and considered a prognostic marker in cancers. Overexpression of Skp2 is frequently observed in patients with Acute lymphoblastic leukemia (ALL). Inhibition of this protein may be a valuable strategy to induce apoptosis in malignant cells. Less well known is the effect of Skp2 inhibition on the potentiation of the chemotherapeutic-induced cell death in B cell precursor acute lymphoblastic leukemia (BCP-ALL). Our results demonstrated that inhibition of the Skp2 using SZL P1-41, not only resulted in caspase-mediated apoptosis but also potentiated doxorubicin-induced apoptosis in BCP-ALL cell lines (NALM-6 and SUP-B15). SZL P1-41 in combination with doxorubicin altered cell cycle distribution and the level of cyclins and CDKs in BCP-ALL cells. DNA damage response genes were also up-regulated in presence of the doxorubicin and SZL P1-41 in both cell lines. In conclusion, our results indicated that inhibition of Skp2 either alone or in a combination with doxorubicin may hold promise in the future treatment of BCP-ALL. This article is protected by copyright. All rights reserved.

Celastrol inhibits the proliferation and induces apoptosis of colorectal cancer cells via downregulating NF-κB/COX-2 signaling pathways

BACKGROUND

Colorectal cancer (CRC) is the third-ranked malignant tumor in the world that contributes to the death of a major population of the world. Celastrol, a bioactive natural product isolated from the medicinal plant Tripterygium wilfordii Hook F, has been proved to be an effective anti-tumor inhibitor for multiple tumors.

OBJECTIVE

To reveal the therapeutic effect and underlying mechanisms of celastrol on CRC cells.

METHODS

CCK-8 and clonogenic assay were used to analyze the cell proliferation in CRC cells. Flow cytometry analysis was conducted to assess the cell cycle and cell apoptosis. Wound-healing and cell invasion assay were used to evaluate the migrating and invasion capability of CRC cells. The potential antitumor mechanism of celastrol was investigated by qPCR, western blot, and confocal immunofluorescence analyses.

RESULTS

Celastrol effectively inhibited CRC cell proliferation by activating caspase-dependent cell apoptosis and facilitating G1 cell cycle arrest in a dose-dependent manner, as well as cell migration and invasion by downregulating the MMP2 and MMP9. Mechanistic protein expression revealed that celastrol suppressed the expression of COX-2 by inhibiting the phosphorylation of NF-κB p65 and subsequently leading to cytoplasmic retention of p65 protein, thereby inhibiting its nuclear translocation and transcription activities.

CONCLUSION

These findings indicate that celastrol is an effective inhibitor for CRC, regulating the NF-κB/COX-2 pathway, leading to the inhibition of cell proliferation characterized by cell cycle arrest and caspase-dependent apoptosis, providing a potential alternative therapeutic agent for CRC patients.

Silencing of Nek2 suppresses the proliferation, migration and invasion and induces apoptosis of breast cancer cells by regulating ERK/MAPK signaling

Breast cancer is a frequent cancer among women. The current study investigated the biological functions of Nek2 in breast cancer and its possible mechanism. The mRNA expression of Nek2 in breast epithelial cells and eight breast cancer cell lines was detected by qRT-PCR. Silencing Nek2 was transfected into MDA-MB-231 and MCF7 cells to examine its roles in the viability, migration, invasion, cell colony, apoptosis and cell cycle of the breast cancer cells by performing CCK-8, wound scratch, Transwell, clone formation and flow cytometry assays, respectively. The expressions of related genes were detected using qRT-PCR and Western blot. MAPK pathway agonist IGF (insulin-like growth factor-1) was added into MDA-MB-231 and MCF7 cells and then cell viability was examined. Nek2 expression was frequently up-regulated in breast cancer cell lines, and silencing Nek2 significantly inhibited the viability, cell migration, invasion and clone formation, promoted cell apoptosis of MDA-MB-231 and MCF7 cells, and arrested cell cycle in G0/G1 phase. Furthermore, knocking down Nek2 decreased the mRNA and protein expressions of Bcl-2, CyclinB1 and CyclinD1, and increased Bax and p27 expressions. Moreover, knocking down Nek2 inhibited the phosphorylation of ERK and p38, and almost completely reversed the expression of p-ERK increased by IGF, but Nek2 knockdown had no obvious effect on p-p38. The inhibitory effect of Nek2 silencing on the cell viability was mainly realized by the inhibition of ERK/MAPK signaling. Nek2 plays an important role in the regulation of the progression of breast cancer in vitro probably through regulating the ERK/MAPK signaling.

ASIC1 and ASIC3 mediate cellular senescence of human nucleus pulposus mesenchymal stem cells during intervertebral disc degeneration

Stem cell approaches have become an attractive therapeutic option for intervertebral disc degeneration (IVDD). Nucleus pulposus mesenchymal stem cells (NP-MSCs) participate in the regeneration and homeostasis of the intervertebral disc (IVD), but the molecular mechanisms governing these processes remain to be elucidated. Acid-sensing ion channels (ASICs) which act as key receptors for extracellular protons in central and peripheral neurons, have been implicated in IVDD where degeneration is associated with reduced microenvironmental pH. Here we show that ASIC1 and ASIC3, but not ASIC2 and ASIC4 are upregulated in human IVDs according to the degree of clinical degeneration. Subjecting IVD-derived NP-MSCs to pH 6.6 culture conditions to mimic pathological IVD changes resulted in decreased cell proliferation that was associated with cell cycle arrest and induction of senescence. Key molecular changes observed were increased expression of p53, p21, p27, p16 and Rb1. Instructively, premature senescence in NP-MSCs could be largely alleviated using ASIC inhibitors, suggesting both ASIC1 and ASIC3 act decisively upstream to activate senescence programming pathways including p53-p21/p27 and p16-Rb1 signaling. These results highlight the potential of ASIC inhibitors as a therapeutic approach for IVDD and broadly define an in vitro system that can be used to evaluate other IVDD therapies.

Avasimibe exerts anticancer effects on human glioblastoma cells via inducing cell apoptosis and cell cycle arrest

Glioblastoma (GBM) is the most common and lethal primary brain tumor in adults, but there is no effective drug available for GBM. Avasimibe is a potent inhibitor of acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1), which was used to treat atherosclerosis. Experimental evidence and bioinformatics have shown that avasimibe has anticancer activity. In this study we investigated the anticancer effects of avasimibe on human glioblastoma cells and the underlying mechanisms. Our results showed that avasimibe dose-dependently inhibited the proliferation of U251 and U87 human glioblastoma cells with IC50 values of 20.29 and 28.27 μM, respectively, at 48 h. Avasimibe (7.5, 15, 30 μM) decreased the DNA synthesis, and inhibited the colony formation of the tumor cells. Treatment of avasimibe also dose-dependently increased the apoptotic rate of tumor cells, decreased the mitochondrial membrane potential, induced the activity of caspase-3/7, and increased the protein expression of cleaved caspase-9, cleaved PARP and Bax in U251 and U87 cells. RNA-sequencing analyses revealed that avasimibe suppressed the expression of CDK2, cyclin E1, CDK4, cyclin D, CDK1, cyclin B1, Aurora A, and PLK1, while induced the expression of p53, p21, p27, and GADD45A, which was validated by Western blot analysis. These results demonstrated that avasimibe induced mitochondria-dependent apoptosis in glioblastoma cells, which was associated with arresting the cell cycle at G0/G1 phase and G2/M phase by regulating the p53/p21 pathway, p53/GADD45A and Aurora A/PLK1 signaling pathways. In U87 xenograft nude mice model, administration of avasimibe (15, 30 mg·kg-1·d-1, ip, for 18 days) dose-dependently inhibit the tumor growth. Taken together, our results demonstrated that avasimibe might be a promising chemotherapy drug in the treatment of GBM.

Expression and DNA methylation profiles of EZH2-target genes in plasma exosomes and matched primary tumor tissues of the patients with diffuse large B-cell lymphoma

AIMS

Diffuse large B-cell lymphoma (DLBCL) is the most common type of aggressive lymphoma. This study was designed to compare epigenetic alterations observed in Enhancer of Zeste Homolog 2 (EZH2)-target genes between plasma-derived exosomes and primary tumors in DLBCL patients.

MAIN METHODS

Exosomes were isolated from plasma of 21 DLBCL patients and 21 controls. We analyzed the methylation status of the target genes using methylation-specific PCR. We also examined whether the exosomes and the tumor samples contained transcripts of the target genes.

KEY FINDINGS

We found that CDKN2A and CDKN2B were methylated in both plasma exosomes and primary tumor tissue samples. None of the transcripts were found in the exosomes except CDKN1B which was expressed in 8 (38%) of the exosome samples.

SIGNIFICANCE

This study showed that plasma exosomes might preferably package certain target molecules from primary tumors and the exosomes containing dual methylated DNAs of CDKN2A and CDKN2B, or CDKN1B transcript may contribute to DLBCL pathogenesis.

Absence of the Shb gene in mixed-lineage leukemia MLL-AF9 cells increases latency in mice despite higher proliferation rates in vitro

Mixed lineage leukemia (MLL) arises from several KMT2A-gene chromosomal translocations. Shb gene deficiency has been found to exhibit pleiotropic effects in different models of leukemia, and consequently, this study aimed to investigate MLL-AF9-induced leukemia in Shb deficiency. Bone marrow cells from wild type and Shb knockout (KO) mice were transduced with the MLL-AF9 gene. Shb KO MLL-AF9 cells proliferated at an increased rate, exhibited altered expression of certain cytokine genes (Kitl, Csf3, IL6, IL1b) and higher expression of cell cycle genes (Ccnd2, Ccne1). Mice receiving Shb KO MLL-AF9 cells showed longer latency without displaying any difference in rates of leukemic cell proliferation, indicating a dichotomy between the in vitro and in vivo phenotypes. The mice with Shb deficient MLL-AF9 cells had a lower content of leukemic bone marrow cells allowing elevated normal hematopoiesis, explaining the longer latency. Finally, Shb knockout GFP-positive bone marrow cells showed a higher percentage of cells expressing myeloid markers. The result suggests a role of Shb in the progression of leukemia and that the relevance of the Shb gene is context-dependent as inferred from the differences between the in vivo and in vitro responses. These findings help to obtain an increased understanding of human MLL-AF9 leukemia.

UBAC2 promotes bladder cancer proliferation through BCRC-3/miRNA-182-5p/p27 axis

Emerging evidences have demonstrated that ubiquitin-associated domain-containing protein 2 (UBAC2) is closely related to the occurrence and development of malignant tumors. However, the functions and underlying molecular mechanisms of UBAC2 in bladder cancer (BC) development have not been defined. In this study, we found that both UBAC2 mRNA and protein levels were upregulated in BC tissues and cell lines, and knockdown of UBAC2 inhibited BC cells proliferation both in vitro and in vivo. Meanwhile, Kaplan-Meier survival plots of 406 BC cases from TCGA database showed that higher expression of UBAC2 in BC patients was associated with lower survival rate. Mechanistic studies revealed that knockdown of UBAC2 increased the expression of p27 by posttranscriptional regulation. Our previous study indicated that circular RNA BCRC-3 (BCRC-3) promoted the expression of p27 through interacting with miR-182-5p, and reversed miR-182-5p-induced inhibition of p27 3'UTR activity. In the present study, we found that UBAC2 could bind to BCRC-3, and subsequently affected the interaction of BCRC-3 with miR-182-5p to inhibit the expression of p27. Furthermore, knockdown of BCRC-3 partly reversed the upregulation of p27 expression induced by knockdown of UBAC2. Our findings highlight a novel mechanism of UBAC2 in regulating p27 through affecting the function of BCRC-3, and provide a research basis for the diagnostic and therapeutic application of BC.

Cantharidin Induces Apoptosis and Promotes Differentiation of AML Cells Through Nuclear Receptor Nur77-Mediated Signaling Pathway

Background

Acute myeloid leukemia (AML) is a hematopoietic malignancy characterized by uncontrolled proliferation and accumulation of myeloblasts in the bone marrow (BM), blood, and other organs. The nuclear receptors Nur77 is a common feature in leukemic blasts and has emerged as a key therapeutic target for AML. Cantharidin (CTD), a main medicinal component of Mylabris (blister beetle), exerts an anticancer effect in multiple types of cancer cells.

Purpose

This study aims to characterize the anti-AML activity of CTD in vitro and in vivo and explore the potential role of Nur77 signaling pathway.

Study Design/Methods

The inhibition of CTD on cell viability was performed in different AML cells, and then the inhibition of CTD on proliferation and colony formation was detected in HL-60 cells. Induction of apoptosis and promotion of differentiation by CTD were further determined. Then, the potential role of Nur77 signaling pathway was assessed. Finally, anti-AML activity was evaluated in NOD/SCID mice.

Results

In our study, CTD exhibited potent inhibition on cell viability and colony formation ability of AML cells. Moreover, CTD significantly induced the apoptosis, which was partially reversed by Z-VAD-FMK. Meanwhile, CTD promoted the cleavage of caspases 8, 3 and PARP in HL-60 cells. Furthermore, CTD obviously suppressed the proliferation and induced the cell cycle arrest of HL-60 cells at G2/M phase. Meanwhile, CTD effectively promoted the differentiation of HL-60 cells. Notably, CTD transiently induced the expression of Nur77 protein. Interestingly, CTD promoted Nur77 translocation from the nucleus to the mitochondria and enhanced the interaction between Nur77 and Bcl-2, resulting in the exposure of the BH3 domain of Bcl-2, which is critical for the conversion of Bcl-2 from an antiapoptotic to a proapoptotic protein. Importantly, silencing of Nur77 attenuated CTD-induced apoptosis, reversed CTD-mediated cell cycle arrest and differentiation of HL-60 cells. Additionally, CTD also exhibited an antileukemic effect in NOD/SCID mice with the injection of HL-60 cells into the tail vein.

Conclusions

Our studies suggest that Nur77-mediated signaling pathway may play a critical role in the induction of apoptosis and promotion of differentiation by CTD on AML cells.

CDK Blockade Using AT7519 Suppresses Acute Myeloid Leukemia Cell Survival through the Inhibition of Autophagy and Intensifies the Anti-leukemic Effect of Arsenic Trioxide

The strong storyline behind the critical role of cyclin-dependent kinase (CDK) inhibitor proteins in natural defense against malignant transformation not only represents a heroic perspective for these proteins, but also provides a bright future for the application of small molecule inhibitors of CDKs in the novel cancer treatment strategies. The results of the present study revealed that the inhibition of CDKs using pan-CDK inhibitor AT7519, as revealed by the induction of G1 cell cycle arrest as well as the reduction of cyclins expression, resulted in decreased survival in acute myeloid leukemia (AML)-derived KG-1 cells, either in the context of single agent or in combination with arsenic trioxide (ATO). Apart from alterations in the expression of proliferation and apoptotic genes, the anti-survival property of AT7519 was coupled with the inhibition of autophagy-related genes. Notably, we found that the blockage of autophagy system in KG-1 cells resulted in a superior cytotoxic effect, introducing autophagy as a probable suppressor of cell death. As far as we are aware, to date, no study has reported the contributory mechanisms correlated with the less sensitivity of acute leukemia cells to AT7519 and our study suggested for the first time that the activation of both PI3K and c-Myc signaling pathways could overshadow, at least partly, the efficacy of this agent in KG-1 cells. Overall, due to the pharmacologic safety of AT7519, our study proposed this inhibitor as a promising agent for the treatment of AML either as a single agent or in a combined-modal strategy.

Dormant tumor cells interact with memory CD8+ T cells in RET transgenic mouse melanoma model

Melanoma is an aggressive form of skin-cancer. Melanoma cells are characterized by their plasticity, resulting in therapy resistance. Using RET transgenic mouse melanoma model, we characterized dormant tumor cells accumulated in the bone marrow (BM) and investigated their interaction with effector memory CD8⁺ T cells. We found that cells expressing melanoma-associated antigen tyrosinase related protein (TRP)-2 and stemness marker CD133 represented less than 1.5% of all melanoma cells in primary skin lesions and metastatic lymph nodes. The majority of these cells were negative for the proliferation marker Ki67. In the BM, CD133⁺TRP-2⁺ melanoma cells displayed an aberrant expression of p16, p27, Ki67 and PCNA proteins, suggesting their dormant phenotype. Moreover, these cells were characterized by an elevated expression of various molecules characterized stemness, metastatic, angiogenic and immunosuppressive properties such as CD271, CD34, HIF-1α, CXCR3, CXCR4, VEGR2, PD-L1, CTLA-4, CD39 and CCR4 as compared to their CD133^- counterparts. Disseminated BM dormant TRP-2⁺ tumor cells were found to be co-localized with memory CD8⁺ T cells. Our data suggest that these dormant melanoma cells in the BM could play an important role in the maintenance of memory T cells in the BM.

Propofol inhibits proliferation and cisplatin resistance in ovarian cancer cells through regulating the microRNA‑374a/forkhead box O1 signaling axis

Ovarian cancer is a prominent disease that demonstrates high incidence rates in women and often presents multidrug resistance. Propofol has been demonstrated to suppress the malignancy of various types of human cancer; however, the underlying molecular mechanisms of propofol in ovarian cancer remain largely unknown. The present study aimed to investigate whether and how propofol inhibits proliferation and cisplatin (DDP) resistance in ovarian cancer cells. Ovarian cancer cell viability was assessed by the Cell Counting kit-8 assay; apoptosis and cell cycle progression were determined by flow cytometry; the relative expression levels of microRNA (miR)-374a and forkhead box O1 (FOXO1) were analyzed using reverse transcription-quantitative PCR; the binding ability of miR-374a to FOXO1 was assessed by the dual-luciferase reporter assay; cellular sensitivity to DDP was detected using the MTT assay; and finally, the protein expression levels of FOXO1, p27, and Bcl-2-like-protein 11 (Bim) were analyzed by western blotting. Propofol reduced viability, promoted apoptosis and decreased miR-374a expression levels in A2780 cells. In addition, the viability of A2780/DDP cells in the propofol + DDP treatment group was significantly inhibited, and the apoptotic rate was increased. In addition, miR-374a overexpression increased cell viability and the proportion of cells in the S phase, and decreased the proportion of cells in the G0/G1 phase. Conversely, genetic knockdown of miR-374a exerted the opposite effects on cell viability and cell cycle progression. Moreover, miR-374a was demonstrated to bind to FOXO1. Propofol promoted the expression of FOXO1, p27 and Bim, induced cell cycle arrest and decreased ovarian cancer cell viability. In addition, treatment with propofol and DDP regulated FOXO1 and increased apoptosis of ovarian cancer cells. In conclusion, propofol downregulated miR-374a and modulated the FOXO1 pathway to reduce proliferation and DDP resistance in ovarian cancer cells.

Toll-like receptor 4 (TLR4) deficiency aggravates dextran sulfate sodium (DSS)-induced intestinal injury by down-regulating IL6, CCL2 and CSF3

Background

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) that causes long-lasting inflammation and ulcers in the human digestive tract. The repair role of TLR4 in the intestinal epithelium is still unknown.

Methods

By comparing to wild-type (WT) mice, Toll-like receptor 4 (TLR4)-knockout mice (TLR4-KO) were used as dextran sulfate sodium (DSS)-induced colitis models to explore the role of TLR4 signaling in intestinal injury. High-throughput RNA-Seq, RT-qPCR and ELISA were performed to screen and verify key differences in gut genes between WT and TLR4-KO mice. Functional study of core dysregulated factors was performed in intestinal cell lines.

Results

We found that DSS-induced intestinal injury was aggravated by LPS (TLR4 agonist) and TLR4-KO. When compared to WT mice, IL6, CCL2, CSF3, IL11, Ccnb1, Ccnd1 and TNF-α significantly decreased and Fas and FasL have increased in the gut of TLR4-KO mice. IL6, CCL2, CSF3, Fas and FasL have all increased in CT-26 cells treated with LPS. Combined with the above data and KEGG enrichment, it can be assumed that TLR4-KO might aggravate DSS-induced intestinal damage by attenuating cell cycle, cytokine-cytokine receptor interaction, and Toll-like receptor signaling pathway, and enhancing the apoptosis pathway. In the functional study of core dysregulated factors, it was found that LPS, IL6, IL11, CSF3, CCL2, S100A8, S100A9 and Mmp3 have improved viability of colon cancer cell lines and decreased apoptosis rate of mouse colon cancer cells when these were treated with DSS. However, Jo-2 (Fas agonistic monoclonal antibody) played the opposite role in colon cancer cells treated with DSS.

Conclusions

TLR4 had a repairing effect on DSS-induced intestinal damage and it up-regulate IL6, CCL2 and CSF3. Fas and FasL enhanced DSS-induced colon injury in mice, but might have little to do with TLR4 signaling.

Implication of myeloid differentiation factor 88 inhibitor TJ-M2010-5 for therapeutic intervention of hepatocellular carcinoma

AIM

Myeloid differentiation factor 88 (MyD88) plays a key role in tumor proliferation and metastasis. Targeting MyD88 is a potent strategy in tumor therapy. TJ-M2010-5 is a small molecule derivative of aminothiazole and could inhibit dimer formation of MyD88. To explore the potential of TJ-M2010-5 in tumor therapy, we determined its antitumor effect and correlate mechanisms of TJ-M2010-5 in hepatocellular carcinoma (HCC).

METHODS

The antitumor effect of intratumoral injection of TJ-M2010-5 to H22 tumor-bearing BALB/c mice was observed. Tumor growth was monitored. The expression of MyD88 and Ki-67 were detected by immunofluorescence. In vitro, the impacts of TJ-M2010-5 on proliferation, cell cycle, necrosis, and apoptosis of H22 cells were evaluated. The direct and indirect effects of TJ-M2010-5 on macrophages were evaluated using flow cytometry.

RESULTS

TJ-M2010-5 induced both G₀ /G₁ and G₁ /S phase arrests in HCC cells. Mechanically, downstream activation of MyD88 was suppressed by TJ-M2010-5 through the extracellular regulated protein kinase-1/2/p90 ribosomal S6 kinase/glycogen synthase kinase-3β signaling pathway. In turn, cyclin-dependent kinase (CDK)6/cyclin D1 and CDK2/cyclin E complexes were downregulated. More importantly, TJ-M2010-5 significantly inhibited tumor growth in mice. Additionally, the portion of antitumor M1 macrophages (F4/80⁺ CD11c⁺ ) in the tumor microenvironment were increased after TJ-M2010-5 treatment. Together, these data indicate that TJ-M2010-5 is a promising therapeutic drug for HCC.

CONCLUSIONS

These results indicate that MyD88 is a feasible target for antitumor treatment and TJ-M2010-5 is a qualified candidate for HCC therapy.

Tandem RNA isolation reveals functional rearrangement of RNA-binding proteins on CDKN1B/p27Kip1 3'UTRs in cisplatin treated cells

Post-transcriptional control of gene expression is mediated via RNA-binding proteins (RBPs) that interact with mRNAs in a combinatorial fashion. While recent global RNA interactome capture experiments expanded the repertoire of cellular RBPs quiet dramatically, little is known about the assembly of RBPs on particular mRNAs; and how these associations change and control the fate of the mRNA in drug-treatment conditions. Here we introduce a novel biochemical approach, termed tobramycin-based tandem RNA isolation procedure (tobTRIP), to quantify proteins associated with the 3ʹUTRs of cyclin-dependent kinase inhibitor 1B (CDKN1B/p27^Kip1) mRNAs in vivo. P27^Kip1 plays an important role in mediating a cell’s response to cisplatin (CP), a widely used chemotherapeutic cancer drug that induces DNA damage and cell cycle arrest. We found that p27^Kip1 mRNA is stabilized upon CP treatment of HEK293 cells through elements in its 3ʹUTR. Applying tobTRIP, we further compared the associated proteins in CP and non-treated cells, and identified more than 50 interacting RBPs, many functionally related and evoking a coordinated response. Knock-downs of several of the identified RBPs in HEK293 cells confirmed their involvement in CP-induced p27 mRNA regulation; while knock-down of the KH-type splicing regulatory protein (KHSRP) further enhanced the sensitivity of MCF7 adenocarcinoma cancer cells to CP treatment. Our results highlight the benefit of specific in vivo mRNA-protein interactome capture to reveal post-transcriptional regulatory networks implicated in cellular drug response and adaptation.

Effects of lentivirus-mediated astrocyte elevated gene-1 overexpression on proliferation and apoptosis of human retinoblastoma cells

PURPOSE

To investigate the effect of astrocyte elevated gene-1 (AEG-1) overexpression on the biological behaviour of human retinoblastoma (RB) cells and its possible mechanism.

METHODS

Three human RB cell lines (SO-RB50, Y79 and WERI-RB1) were infected with AEG-1-GFP recombinant lentiviral vectors to induce AEG-1 overexpression, while the cells infected with negative lentiviral vectors and cells without any intervention formed control groups.

RESULTS

All three RB cell lines showed an overexpression of AEG-1 after lentivirus infection (p < 0.001 for all three cell lines). The survival rate of RB cells increased (all p < 0.001) in the AEG-1 overexpressed groups when compared with the control groups. There was a decrease in G0/G1 cell cycle phase arrest and an accumulation in G2/M cell cycle phase in all three RB cell lines (p < 0.001), with an induction in the S phase in WERI-RB1 cells. It was paralleled by a downregulation of p21 and p27 proteins and an upregulation of the Cdc2 protein. The apoptosis rate of RB cells declined (p < 0.001) when AEG-1 was overexpressed, in association with an upregulation of Bcl-2 protein and a downregulation of Bax protein and cleaved caspase-3 proteins.

CONCLUSIONS

A lentivirus-mediated AEG-1 overexpression in RB cells led in vitro to a growth promotion and an apoptosis inhibition of human RB cells, associated with an upregulation of the Bcl-2 protein, a downregulation of the Bax protein and of cleaved caspase-3 proteins, and with alterations of the cell cycle. AEG-1 may be involved in the development and progression of RB.

Effects of paclitaxel intervention on pulmonary vascular remodeling in rats with pulmonary hypertension

The aim of the present study was to investigate the effects of paclitaxel (PTX), at a non-cytotoxic concentration, on pulmonary vascular remodeling (PVR) in rats with pulmonary hypertension (PAH), and to explore the mechanisms underlying the PTX-mediated reversal of PVR in PAH. A total of 36 rats were divided into control group (n=12), model group (n=12) receiving a subcutaneous injection of monocrotaline (60 mg/kg) in the back on day 7 following left pneumonectomy and PTX group (n=12) with PTX (2 mg/kg) injection via the caudal vein 3 weeks following establishing the model. The degree of PVR among all groups, as well as the expression levels of Ki67, p27^Kip1 and cyclin B1, were compared. The mean pulmonary artery pressure, right ventricular hypertrophy index [right ventricle/(left ventricle + septum) ratio] and the thickness of the pulmonary arterial tunica media in the model group were 58.34±2.01 mmHg, 0.64±0.046 and 65.3±3.3%, respectively, which were significantly higher when compared with 23.30±1.14 mmHg, 0.32±0.028 and 16.2±1.3% in the control group, respectively (P<0.01). The mean pulmonary artery pressure, right ventricular hypertrophy index and thickness of the pulmonary arterial tunica media in the PTX group were 42.35±1.53 mmHg, 0.44±0.029 and 40.5±2.6%, respectively, which were significantly lower when compared with the model group (P<0.01). Compared with the control group, the expression levels of Ki67 and cyclin B1 in the model group were significantly increased (P<0.01), while p27^Kip1 expression was significantly reduced (P<0.01). Following PTX intervention, the expression levels of Ki67 and cyclin B1 were significantly reduced when compared with the model group (P<0.01), while p27^Kip1 expression was significantly increased (P<0.01). The results of the present study suggest that PTX, administered at a non-cytotoxic concentration, may reduce PAH in rats, and prevent the effects of PVR in PAH. These effects of PTX may be associated with increased expression of p27^Kip1 and decreased expression of cyclin B1.

Nonylphenol promotes the proliferation of colorectal cancer COLO205 cells by upregulating the expression of protein kinase C ζ

Previous studies have indicated the potential role of estrogen in the development and prognosis of colorectal cancer (CRC). Nonylpheno (NP) is an endocrine-disrupting chemical, which may influence the development of estrogen-dependent types of cancer. However, the molecular mechanism of NP in the development of CRCs remains unclear. In the present study, various concentrations of NP were used to treat COLO205 CRC cells, and the expression of protein kinase C ζ (PKCζ) was knocked down using PKCζ small interfering RNA. The effects of NP in various concentrations on the cell cycle and apoptosis of COLO205 cells were examined, and the change in the expression level of PKCζ was analyzed. The results indicated that NP may significantly induce proliferation of COLO205 CRC cells, and significantly reduce cell apoptosis. However, suppression of PKCζ expression may inhibit proliferation, while NP could reduce this inhibition. The results of a western blot analysis indicated that the expression level of cyclin D1 and E were significantly increased following NP treatment, and the expression of p27 was significantly decreased. The phosphorylation of PKCζ and extracellular-signal-regulated kinase (ERK)1/2 was significantly increased following NP treatment in a dose-dependent manner. Overall, NP induced human CRC COLO205 cell proliferation and inhibited the apoptotic rate of COLO205 cells by increasing the activity of PKCζ and ERK1/2.

Evolution of Our Understanding of the Hyperparathyroid Syndromes: A Historical Perspective

We review advancing and overlapping stages for our understanding of the expressions of six hyperparathyroid (HPT) syndromes: multiple endocrine neoplasia type 1 (MEN1) or type 4, multiple endocrine neoplasia type 2A (MEN2A), hyperparathyroidism-jaw tumor syndrome, familial hypocalciuric hypercalcemia, neonatal severe primary hyperparathyroidism, and familial isolated hyperparathyroidism. During stage 1 (1903 to 1967), the introduction of robust measurement of serum calcium was a milestone that uncovered hypercalcemia as the first sign of dysfunction in many HPT subjects, and inheritability was reported in each syndrome. The earliest reports of HPT syndromes were biased toward severe or striking manifestations. During stage 2 (1959 to 1985), the early formulations of a syndrome were improved. Radioimmunoassays (parathyroid hormone [PTH], gastrin, insulin, prolactin, calcitonin) were breakthroughs. They could identify a syndrome carrier, indicate an emerging tumor, characterize a tumor, or monitor a tumor. During stage 3 (1981 to 2006), the assembly of many cases enabled recognition of further details. For example, hormone non-secreting skin lesions were discovered in MEN1 and MEN2A. During stage 4 (1985 to the present), new genomic tools were a revolution for gene identification. Four principal genes ("principal" implies mutated or deleted in 50% or more probands for its syndrome) (MEN1, RET, CASR, CDC73) were identified for five syndromes. During stage 5 (1993 to the present), seven syndromal genes other than a principal gene were identified (CDKN1B, CDKN2B, CDKN2C, CDKN1A, GNA11, AP2S1, GCM2). Identification of AP2S1 and GCM2 became possible because of whole-exome sequencing. During stages 4 and 5, the newly identified genes enabled many studies, including robust assignment of the carriers and non-carriers of a mutation. Furthermore, molecular pathways of RET and the calcium-sensing receptor were elaborated, thereby facilitating developments in pharmacotherapy. Current findings hold the promise that more genes for HPT syndromes will be identified and studied in the near future. © 2018 American Society for Bone and Mineral Research.

P27 Protects Cardiomyocytes from Sepsis via Activation of Autophagy and Inhibition of Apoptosis

BACKGROUND It has been reported that p27Kip1 plays an important role not only in the inhibition of cyclin-dependent kinases but also in the regulation of autophagy under various metabolically related stress conditions, including glucose deprivation and endoplasmic reticulum stress. However, its effect on lipopolysaccharide (LPS)-induced cardiomyocyte stress in vitro remains unclear. Here, we measured the increased expression of LC3-II and visualized autophagosomes in vitro by immunofluorescent assays after treatment with a p27 fusion protein. MATERIAL AND METHODS Cardiomyocyte contractile properties were assessed by measuring cell shortening and re-lengthening. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Western blot, colorectal ligation puncture (CLP) surgery, silencing of Atg5 expression by small interfering RNA (siRNA), and immunofluorescent assays were also performed in this study. RESULTS After exogenous delivery of the p27 fusion protein and overexpression of p27 in LPS-induced cardiomyocytes, we found lower expressions of caspase-3 and caspase-8 and reduced positive TUNEL staining. Improved cardiomyocyte mechanical functions and reduced apoptosis were diminished after treatment with various autophagy inhibitors. Intravenous injections of p27-expressing adeno-associated virus serotype 9 (AAV9) vectors resulted in cardiac specific overexpression of p27, and echocardiography was used to assess cardiac function and structure in sepsis rat models. We observed improved cardiac function and reversed adverse ventricular remolding after the introduction of AAV9 vectors. Meanwhile, apoptosis was reduced, and expression of LC3-II was elevated in septic rat models treated with AAV9 vectors compared to controls. CONCLUSIONS The study data demonstrated that the overexpression of p27 protects cardiomyocytes from sepsis-induced cardiac depression via the activation of autophagy and inhibition of apoptosis.

p27 inhibits CDK6/CCND1 complex formation resulting in cell cycle arrest and inhibition of cell proliferation

p27 plays critical roles in cell proliferation, differentiation, and apoptosis, which have been well studied in mammals and Drosophila. However, the mechanisms underlying p27 regulation of the cell cycle have not been thoroughly researched. In this study, Genevestigator, Kaplan-Meier Plotter, and the Human Protein Atlas databases were used to analyze the expression of p27, cell division protein kinase 6 (CDK6), and cyclin D1 (CCND1), as well as its prognostic value in different tumor tissues and corresponding normal tissues. Quantitative PCR and immunohistochemistry were used to detect the expression of p27, CDK6, and CCND1 in the tissues of cancer patients. The effects of p27, CDK6, and CCND1 on the proliferation of lung cancer cells were examined by the MTT assay, and flow cytometry was used to investigate the mechanism by which p27 affected cell proliferation. Immunofluorescence, co-immunoprecipitation, and Western blotting were used to determine if p27 interacted with CDK and CCND1 to regulate the cell cycle. The results showed that p27, CDK6, and CCND1 played different roles in tumorigenesis and development, which are in accordance with CDK6 and CCND1 in affecting the cell cycle and cell proliferation. p27 regulated the cell cycle and inhibited cell proliferation by affecting formation of the cell cycle-dependent complex CDK6/CCND1, but did not directly affect the expression of CDK6 and CCND1. Moreover, CCND1 did not regulate the cell cycle alone, but rather, functioned together with CDK6. This study provides insights into the effects of p27 on tumor formation and development, and the underlying regulatory mechanisms.

The 19q13 KRAB Zinc-finger protein ZFP82 suppresses the growth and invasion of esophageal carcinoma cells through inhibiting NF-κB transcription and inducing apoptosis

AIM

To study the epigenetic alternations and biological functions of ZFP82 in esophageal squamous cell carcinoma.

MATERIALS & METHODS

Analysis of ZFP82 expression was carried out by quantitative real-time PCR. Cell function was tested by MTS cell proliferation assay, transwell assay and flow cytometry. Gene mechanisms were studied by reverse transcription-PCR (RT-PCR), quantitative real-time PCR, luciferase reporter assay and Western blot.

RESULTS

ZFP82 promoter methylation was downregulated in esophageal squamous cell carcinoma. ZFP82 ectopic expression suppressed cell function and regulated NF-κB phosphorylation and genes involved in cell cycle arrest and apoptosis. Moreover, ZFP82 methylation was correlated with age, tumor stage and outcome.

CONCLUSION

ZFP82 is a tumor suppressor and is disrupted by promoter CpG methylation during esophageal carcinogenesis.

The prognostic potential of coilin in association with p27 expression in pediatric acute lymphoblastic leukemia for disease relapse

Background

Cajal body (CB) is a nucleic organelle where small nuclear ribonucleoproteins undergo modification, maturation, splicing and/or assembly. Coilin is the marker structural protein of CBs. The expression level and cellular localization of coilin is sensitive to chemotherapeutic reagents, such as cisplatin. The gene of cyclin-dependent kinase inhibitor 1B (p27) is located with a high incidence translocation region of leukemic chromosomes, and its expression was of prognosis values in a variety of adult leukemia types. The exact profile and associated functions of coilin, as well as p27, in children’s acute lymphoblastic leukemia (ALL) is obscure.

Methods

Bone marrow samples from 144 patients with ALL were collected. The expression levels of coilin and p27 were detected by qRT-PCR. The patient cohort was divided into low and high groups of coilin and p27 respectively. The prognosis and clinicobiological characteristics of different groups were investigated, especially focused on the treatment outcome. Leukemia cells of Reh or RS4;11 were exposed to different concentrations of DNR, prior to the detection for morphological changes of coilin by immunofluorescence. In Reh cells, lentivirus sh-coilin was used to silence coilin expression. Western blotting was used to detect coilin and p27 expression; flow cytometry was used for cell cycle and apoptosis assay; MTS method was used for measuring cell viability to examine the drug sensitivity of DNR.

Results

In this study, we found that daunorubicin was able to induce significant morphological changes of CBs in Reh and RS4;11 cells. Knockdown the expression of coilin increased the sensitivity to daunorubicin and inhibited the expression of p27 in Reh cells, and led to increased apoptosis. Importantly, not only the levels of coilin and p27 mRNA expression at initial diagnosis ALL children are markedly higher than those at complete remission (CR), but also both coilin and p27 expression in the relapsed patients was observed significantly higher comparing to the continuous CR patients. The 4-year EFS and RFS indicated that low levels of both coilin and p27 group favored better prognosis (p < 0.05).

Conclusions

Our results indicated that consideration of coilin and p27 levels could be a prognostic reference for predicting the outcome of pediatric ALL patients, especially for disease recurrence. Reduction of coilin expression was sufficient to increase the sensitivity of leukemic cells to daunorubicin treatments, and during which possibly involved functions of p27 in cell cycle regulation and its effects on cell apoptosis.

SAMHD1 modulates in vitro proliferation of acute myeloid leukemia-derived THP-1 cells through the PI3K-Akt-p27 axis

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a mammalian dNTP hydrolase that acts as a negative regulator in the efficacy of cytarabine treatment against acute myeloid leukemia (AML). However, the role of SAMHD1 in AML development and progression remains unknown. We have reported that SAMHD1 knockout (KO) in the AML-derived THP-1 cells results in enhanced proliferation and reduced apoptosis, but the underlying mechanisms are unclear. Here we show that SAMHD1 KO in THP-1 cells increased PI3K activity and reduced expression of the tumor suppressor PTEN. Pharmacological inhibition of PI3K activity reduced cell proliferation specifically in SAMHD1 KO cells, suggesting that SAMHD1 KO-induced cell proliferation is mediated via enhanced PI3K signaling. However, PI3K inhibition did not significantly affect SAMHD1 KO-reduced apoptosis, implicating the involvement of additional mechanisms. SAMHD1 KO also led to enhanced phosphorylation of p27 at residue T157 and its mis-localization to the cytoplasm. Inhibition of PI3K activity reversed these effects, indicating that SAMHD1 KO-induced changes in p27 phosphorylation and localization is mediated via PI3K-Akt signaling. While SAMHD1 KO significantly enhanced THP-1 cell migration in vitro, SAMHD1 KO attenuated the ability of THP-1 cells to form subcutaneous tumors in xenografted immunodeficient mice. This effect correlated with significantly increased expression of tumor necrosis factor α (TNF-α) in tumors, which may suggest that TNF-α-mediated inflammation could account for the decreased tumorigenicity in vivo. Our findings implicate that SAMHD1 can regulate AML cell proliferation via modulation of the PI3K-Akt-p27 signaling axis, and that SAMHD1 may affect tumorigenicity by downregulating inflammation.

Therapeutic Targeting of mTOR in T-Cell Acute Lymphoblastic Leukemia: An Update

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive blood malignancy that arises from the clonal expansion of transformed T-cell precursors. Although T-ALL prognosis has significantly improved due to the development of intensive chemotherapeutic protocols, primary drug-resistant and relapsed patients still display a dismal outcome. In addition, lifelong irreversible late effects from conventional therapy are a growing problem for leukemia survivors. Therefore, novel targeted therapies are required to improve the prognosis of high-risk patients. The mechanistic target of rapamycin (mTOR) is the kinase subunit of two structurally and functionally distinct multiprotein complexes, which are referred to as mTOR complex 1 (mTORC1) and mTORC2. These two complexes regulate a variety of physiological cellular processes including protein, lipid, and nucleotide synthesis, as well as autophagy in response to external cues. However, mTOR activity is frequently deregulated in cancer, where it plays a key oncogenetic role driving tumor cell proliferation, survival, metabolic transformation, and metastatic potential. Promising preclinical studies using mTOR inhibitors have demonstrated efficacy in many human cancer types, including T-ALL. Here, we highlight our current knowledge of mTOR signaling and inhibitors in T-ALL, with an emphasis on emerging evidence of the superior efficacy of combinations consisting of mTOR inhibitors and either traditional or targeted therapeutics.

Role of p27Kip1 as a transcriptional regulator

The protein p27Kip1 is a member of the Cip/Kip family of cyclin-dependent kinase (Cdk) inhibitors. It interacts with both the catalytic and the regulatory subunit (cyclin) and introduces a region into the catalytic cleave of the Cdk inducing its inactivation. Its inhibitory capacity can be modulated by specific tyrosine phosphorylations. p27Kip1 also behaves as a transcriptional regulator. It associates with specific chromatin domains through different transcription factors. ChIP on chip, ChIP-seq and expression microarray analysis allowed the identification of the transcriptional programs regulated by p27Kip1. Thus, important cellular functions as cell division cycle, respiration, RNA processing, translation and cell adhesion, are under p27Kip1 regulation. Moreover, genes involved in pathologies as cancer and neurodegeneration are also regulated by p27Kip1, suggesting its implication in these pathologies. The carboxyl moiety of p27Kip1 can associate with different proteins, including transcriptional regulators. In contrast, its NH2-terminal region specifically interacts with cyclin-Cdk complexes. The general mechanistic model of how p27Kip1 regulates transcription is that it associates by its COOH region to the transcriptional regulators on the chromatin and by the NH2-domain to cyclin-Cdk complexes. After Cdk activation it would phosphorylate the specific targets on the chromatin leading to gene expression. This model has been demonstrated to apply in the transcriptional regulation of p130/E2F4 repressed genes involved in cell cycle progression. We summarize in this review our current knowledge on the role of p27Kip1 in the regulation of transcription, on the transcriptional programs under its regulation and on its relevance in pathologies as cancer and neurodegeneration.

Recognition of Recurrent Protein Expression Patterns in Pediatric Acute Myeloid Leukemia Identified New Therapeutic Targets

Heterogeneity in the genetic landscape of pediatric acute myeloid leukemia (AML) makes personalized medicine challenging. As genetic events are mediated by the expression and function of proteins, recognition of recurrent protein patterns could enable classification of pediatric AML patients and could reveal crucial protein dependencies. This could help to rationally select combinations of therapeutic targets. To determine whether protein expression levels could be clustered into functionally relevant groups, custom reverse-phase protein arrays were performed on pediatric AML (n = 95) and CD34⁺ normal bone marrow (n = 10) clinical specimens using 194 validated antibodies. To analyze proteins in the context of other proteins, all proteins were assembled into 31 protein functional groups (PFG). For each PFG, an optimal number of protein clusters was defined that represented distinct transition states. Block clustering analysis revealed strong correlations between various protein clusters and identified the existence of 12 protein constellations stratifying patients into 8 protein signatures. Signatures were correlated with therapeutic outcome, as well as certain laboratory and demographic characteristics. Comparison of acute lymphoblastic leukemia specimens from the same array and AML pediatric patient specimens demonstrated disease-specific signatures, but also identified the existence of shared constellations, suggesting joint protein deregulation between the diseases.Implication: Recognition of altered proteins in particular signatures suggests rational combinations of targets that could facilitate stratified targeted therapy. Mol Cancer Res; 16(8); 1275-86. ©2018 AACRSee related article by Hoff et al., p. 1263.

ZNF521 sustains the differentiation block in MLL-rearranged acute myeloid leukemia

Zinc finger protein 521 (ZNF521) is a multiple zinc finger transcription factor and a strong candidate as regulator of hematopoietic stem cell homeostasis. Recently, independent gene expression profile studies have evidenced a positive correlation between ZNF521 mRNA overexpression and MLL-rearranged acute myeloid leukemia (AML), leaving open the question on the role of ZNF521 in this subtype of leukemia. In this study, we sought to analyze the effect of ZNF521 depletion on MLL-rearranged AML cell lines and MLL-AF9 xenograft primary cells. Knockdown of ZNF521 with short-hairpin RNA (shRNA) led to decreased leukemia proliferation, reduced colony formation and caused cell cycle arrest in MLL-rearranged AML cell lines. Importantly, we showed that loss of ZNF521 substantially caused differentiation of both MLL-rearranged cell lines and primary cells. Moreover, gene profile analysis in ZNF521-silenced THP-1 cells revealed a loss of MLL-AF9-directed leukemic signature and an increase of the differentiation program. Finally, we determined that both MLL-AF9 and MLL-ENL fusion proteins directly interacted with ZNF521 promoter activating its transcription. In conclusion, our findings identify ZNF521 as a critical effector of MLL fusion proteins in blocking myeloid differentiation and highlight ZNF521 as a potential therapeutic target for this subtype of leukemia.

RRD-251 enhances all-trans retinoic acid (RA)-induced differentiation of HL-60 myeloblastic leukemia cells

All-trans-retinoic acid (RA) is known to induce terminal granulocytic differentiation and cell cycle arrest of HL-60 cells. Responding to an RA-induced cytosolic signaling machine, c-Raf translocates to the nucleus, providing propulsion for RA-induced differentiation. This novel mechanism is not understood, but presumably reflects c-Raf binding with nuclear gene regulatory proteins. RRD-251 is a small molecule that prevents the interaction of c-Raf and RB, the retinoblastoma tumor suppressor protein. The involvement of c-Raf and RB in RA-induced differentiation motivates interest in the effects of combined RA and RRD-251 treatment on leukemic cell differentiation.

We demonstrate that RRD-251 enhances RA-induced differentiation. Mechanistically, we find that nuclear translocated c-Raf associates with pS608 RB. RA causes loss of pS608 RB, where cells with hypophosphorylated S608 RB are G_0/G₁ restricted. Corroborating the pS608 RB hypophosphorylation, RB sequestration of E2F increased with concomitant loss of cdc6 expression, which is known to be driven by E2F. Hypophosphorylation of S608 RB releases c-Raf from RB sequestration to bind other nuclear targets. Release of c-Raf from RB sequestration results in enhanced association with GSK-3 which is phosphorylated at its S21/9 inhibitory sites. c-Raf binding to GSK-3 is associated with dissociation of GSK-3 and RARα, thereby relieving RARα of GSK-3 inhibition. RRD-251 amplifies each of these RA-induced events. Consistent with the posited enhancement of RARα transcriptional activity by RRD-251, RRD-251 increases the RARE-driven CD38 expression per cell. The RA/c-Raf/GSK-3/RARα axis emerges as a novel differentiation regulatory mechanism susceptible to RRD-251, suggesting enhancing RA-effects with RRD-251 in therapy.

Shear-induced Notch-Cx37-p27 axis arrests endothelial cell cycle to enable arterial specification

Establishment of a functional vascular network is rate-limiting in embryonic development, tissue repair and engineering. During blood vessel formation, newly generated endothelial cells rapidly expand into primitive plexi that undergo vascular remodeling into circulatory networks, requiring coordinated growth inhibition and arterial-venous specification. Whether the mechanisms controlling endothelial cell cycle arrest and acquisition of specialized phenotypes are interdependent is unknown. Here we demonstrate that fluid shear stress, at arterial flow magnitudes, maximally activates NOTCH signaling, which upregulates GJA4 (commonly, Cx37) and downstream cell cycle inhibitor CDKN1B (p27). Blockade of any of these steps causes hyperproliferation and loss of arterial specification. Re-expression of GJA4 or CDKN1B, or chemical cell cycle inhibition, restores endothelial growth control and arterial gene expression. Thus, we elucidate a mechanochemical pathway in which arterial shear activates a NOTCH-GJA4-CDKN1B axis that promotes endothelial cell cycle arrest to enable arterial gene expression. These insights will guide vascular regeneration and engineering.

Smad7 protects against acute kidney injury by rescuing tubular epithelial cells from the G1 cell cycle arrest

Smad7 plays a protective role in chronic kidney disease; however, its role in acute kidney injury (AKI) remains unexplored. Here, we report that Smad7 protects against AKI by rescuing the G1 cell cycle arrest of tubular epithelial cells (TECs) in ischemia/reperfusion-induced AKI in mice in which Smad7 gene is disrupted or restored locally into the kidney. In Smad7 gene knockout (KO) mice, more severe renal impairment including higher levels of serum creatinine and massive tubular necrosis was developed at 48 h after AKI. In contrast, restored renal Smad7 gene locally into the kidney of Smad7 KO mice protected against AKI by promoting TEC proliferation identified by PCNA+ and BrdU+ cells. Mechanistic studies revealed that worsen AKI in Smad7 KO mice was associated with a marked activation of TGF-β/Smad3-p21/p27 signaling and a loss of CDK2/cyclin E activities, thereby impairing TEC regeneration at the G1 cell cycle arrest. In contrast, restored Smad7 locally into the kidneys of Smad7 KO mice protected TECs from the G1 cell cycle arrest and promoted TEC G1/S transition via a CDK2/cyclin E-dependent mechanism. In conclusion, Smad7 plays a protective role in AKI. Blockade of TGF-β/Smad3-p21/p27-induced G1 cell cycle arrest may be a key mechanism by which Smad7 treatment inhibits AKI. Thus, Smad7 may be a novel therapeutic agent for AKI.

oxLDL induces endothelial cell proliferation via Rho/ROCK/Akt/p27kip1 signaling: opposite effects of oxLDL and cholesterol loading

Oxidized modifications of LDL (oxLDL) play a key role in the development of endothelial dysfunction and atherosclerosis. However, the underlying mechanisms of oxLDL-mediated cellular behavior are not completely understood. Here, we compared the effects of two major types of oxLDL, copper-oxidized LDL (Cu²⁺-oxLDL) and lipoxygenase-oxidized LDL (LPO-oxLDL), on proliferation of human aortic endothelial cells (HAECs). Cu²⁺-oxLDL enhanced HAECs' proliferation in a dose- and degree of oxidation-dependent manner. Similarly, LPO-oxLDL also enhanced HAEC proliferation. Mechanistically, both Cu²⁺-oxLDL and LPO-oxLDL enhance HAEC proliferation via activation of Rho, Akt phosphorylation, and a decrease in the expression of cyclin-dependent kinase inhibitor 1B (p27^kip1). Both Cu²⁺-oxLDL or LPO-oxLDL significantly increased Akt phosphorylation, whereas an Akt inhibitor, MK2206, blocked oxLDL-induced increase in HAEC proliferation. Blocking Rho with C3 or its downstream target ROCK with Y27632 significantly inhibited oxLDL-induced Akt phosphorylation and proliferation mediated by both Cu²⁺- and LPO-oxLDL. Activation of RhoA was blocked by Rho-GDI-1, which also abrogated oxLDL-induced Akt phosphorylation and HAEC proliferation. In contrast, blocking Rac1 in these cells had no effect on oxLDL-induced Akt phosphorylation or cell proliferation. Moreover, oxLDL-induced Rho/Akt signaling downregulated cell cycle inhibitor p27^kip1 Preloading these cells with cholesterol, however, prevented oxLDL-induced Akt phosphorylation and HAEC proliferation. These findings provide a new understanding of the effects of oxLDL on endothelial proliferation, which is essential for developing new treatments against neovascularization and progression of atherosclerosis.

TRIM22 confers poor prognosis and promotes epithelial-mesenchymal transition through regulation of AKT/GSK3β/β-catenin signaling in non-small cell lung cancer

Expression pattern and biological roles of TRIM22 remains unknown in most human cancers. The present study aims to discover its clinical significance and function in human non-small cell lung cancer (NSCLC). Immunohistochemistry was used to examine TRIM22 expression in 126 cases of NSCLC specimens. TRIM22 protein was upregulated in 70/126 (55.6%) non-small cell lung cancer tissues compared with normal lung tissue. TRIM22 overexpression was associated with advanced TNM stage, positive nodal metastasis and poor prognosis. Plasmid and siRNA transfection were performed in lung cancer cell lines. TRIM22 overexpression promoted proliferation, colony formation and invasion in A549 cells. While its depletion exhibited the opposite effects in H1299 cell line. TRIM22 overexpression promoted cell cycle progression through regulation of cyclin D1, cyclin E and p27. TRIM22 also changed the expression of epithelial to mesenchymal transition (EMT) markers including E-cadherin N-cadherin, Vimentin and Snail. Furthermore, TRIM22 activated PI3K/AKT/GSK3β/β-catenin oncogenic signaling pathways. Treatment with PI3K inhibitor LY294002 and β-catenin siRNA blocked the effects of TRIM22 on EMT in TRIM22-overexpressing cells. In conclusion,TRIM22 serves as an important oncoprotein and a promoter of cell proliferation and invasion through AKT/ GSK3β/β-catenin induced EMT in NSCLC.

A single nucleotide polymorphism of cyclin-dependent kinase inhibitor 1B (p27Kip1) associated with human vein graft failure affects growth of human venous adventitial cells but not smooth muscle cells

BACKGROUND

Cyclin-dependent kinase inhibitor 1B (p27^Kip1) is a cell-cycle inhibitor whose -838C>A single nucleotide polymorphism (rs36228499; hereafter called p27 SNP) has been associated with the clinical failure of peripheral vein grafts, but the functional effects of this SNP have not been demonstrated.

METHODS

Human saphenous vein adventitial cells and intimal/medial smooth muscle cells (SMCs) were derived from explants obtained at the time of lower extremity bypass operations. We determined the following in adventitial cells and SMCs as a function of the p27 SNP genotype: (1) p27 promoter activity, (2) p27 messenger (m)RNA and protein levels, and (3) growth and collagen gel contraction. Deoxyribonuclease I footprinting was also performed in adventitial cells and SMCs.

RESULTS

p27 promoter activity, deoxyribonuclease I footprinting, p27 mRNA levels, and p27 protein levels demonstrated that the p27 SNP is functional in adventitial cells and SMCs. Both cell types with the graft failure protective AA genotype had more p27 mRNA and protein. As predicted because of higher levels of p27 protein, adventitial cells with the AA genotype grew slower than those of the CC genotype. Unexpectedly, SMCs did not show this genotype-dependent growth response.

CONCLUSIONS

These results support the functionality of the p27 SNP in venous SMCs and adventitial cells, but an effect of the SNP on cell proliferation is limited to only adventitial cells. These data point to a potential role for adventitial cells in human vein graft failure and also suggest that SMCs express factors that interfere with the activity of p27.

Glutathione peroxidase 7 suppresses cancer cell growth and is hypermethylated in gastric cancer

Gastric cancer (GC) is one of the most common cancers in the world, and remains the third leading cause of cancer-related deaths worldwide. Glutathione peroxidase 7 (GPX7) is a member of GPX family which is downregulated in some cancer types. In this study, we investigated the expression, regulation, and molecular function of GPX7 in gastric cancer using 2D and 3D in vitro models and de-identified human tissue samples. Quantitative real-time RT-PCR, immunofluorescence, Western blot, 3D organotypic cultures, and pyrosequencing assays were used. We detected downregulation of GPX7 in all 7 gastric cancer cell lines that we tested and in approximately half (22/45) of human gastric cancer samples, as compared to histologically normal gastric tissues. Quantitative bisulfite pyrosequencing methylation analysis demonstrated DNA hypermethylation (> 10% methylation level) of GPX7 promoter in all 7 gastric cancer cell lines and in 56% (25/45) of gastric cancer samples, as compared to only 13% (6/45) in normal samples (p < 0.0001). Treatment of AGS and SNU1 cells with 5-Aza-2′-deoxycytidine led to a significant demethylation of GPX7 promoter and restored the expression of GPX7. In vitro assays showed that reconstitution of GPX7 significantly suppressed gastric cancer cell growth in both 2D and 3D organotypic cell culture models. This growth suppression was associated with inhibition of cell proliferation and induction of cell death. We detected significant upregulation of p27 and cleaved PARP and downregulation of Cyclin D1 upon reconstitution of GPX7. Taken together, we conclude that epigenetic silencing of GPX7 could play an important role in gastric tumorigenesis and progression.

Lentivirus-mediated knockdown of P27RF-Rho inhibits hepatocellular carcinoma cell growth

Aim of the study

To investigate the effects of P27RF-Rho on hepatocellular carcinoma (HCC) cell growth and explore the possibility of using it as a novel therapeutic target for liver cancer treatment.

Material and methods

P27RF-Rho in HCC cells was silenced by lentivirus-mediated RNA interference, and the silencing effect was verified by RT-PCR. Cell proliferation was determined by MTT and clone formation assay. Cell cycle phase and apoptosis were detected through FACS. The expression level of cell growth, apoptosis, and metastasis associated genes was detected by quantitative PCR.

Results

Lentivirus-mediated P27RF-Rho knockdown inhibited HCC cell growth and clone formation. P27RF-Rho silence induced cell cycle arrest and apoptosis. The mRNA level of genes associated with cell cycle, apoptosis, and invasion also significantly altered after P27RF-Rho knockdown. Cyclin A, CDK2, BCL-2, and MMP-9 were down-regulated. P27 and Bax were up-regulated.

Conclusions

P27RF-Rho knockdown inhibits HCC cell growth, and P27RF-Rho is probably a promising target for HCC treatment.

Hypoglycemia Enhances Epithelial-Mesenchymal Transition and Invasiveness, and Restrains the Warburg Phenotype, in Hypoxic HeLa Cell Cultures and Microspheroids

The accelerated growth of solid tumors leads to episodes of both hypoxia and hypoglycemia (HH) affecting their intermediary metabolism, signal transduction, and transcriptional activity. A previous study showed that normoxia (20% O₂ ) plus 24 h hypoglycemia (2.5 mM glucose) increased glycolytic flux whereas oxidative phosphorylation (OxPhos) was unchanged versus normoglycemia in HeLa cells. However, the simultaneous effect of HH on energy metabolism has not been yet examined. Therefore, the effect of hypoxia (0.1-1% O₂ ) plus hypoglycemia on the energy metabolism of HeLa cells was analyzed by evaluating protein content and activity, along with fluxes of both glycolysis and OxPhos. Under hypoxia, in which cell growth ceased and OxPhos enzyme activities, ΔΨm and flux were depressed, hypoglycemia did not stimulate glycolytic flux despite increasing H-RAS, p-AMPK, GLUT1, GLUT3, and HKI levels, and further decreasing mitochondrial enzyme content. The impaired mitochondrial function in HH cells correlated with mitophagy activation. The depressed OxPhos and unchanged glycolysis pattern was also observed in quiescent cells from mature multicellular tumor spheroids, suggesting that these inner cell layers are similarly subjected to HH. The principal ATP supplier was glycolysis for HH 2D monolayer and 3D quiescent spheroid cells. Accordingly, the glycolytic inhibitors iodoacetate and gossypol were more effective than mitochondrial inhibitors in decreasing HH-cancer cell viability. Under HH, stem cell-, angiogenic-, and EMT-biomarkers, as well as glycoprotein-P content and invasiveness, were also enhanced. These observations indicate that HH cancer cells develop an attenuated Warburg and pronounced EMT- and invasive-phenotype. J. Cell. Physiol. 232: 1346-1359, 2017. © 2016 Wiley Periodicals, Inc.

C-reactive protein promotes acute kidney injury via Smad3-dependent inhibition of CDK2/cyclin E

Acute kidney injury (AKI) is exacerbated in C-reactive protein transgenic mice but alleviated in Smad3 knockout mice. Here we used C-reactive protein transgenic/Smad3 wild-type and C-reactive protein transgenic/Smad3 knockout mice to investigate the signaling mechanisms by which C-reactive protein promotes AKI. Serum creatinine was elevated, and the extent of tubular epithelial cell necrosis following ischemia/reperfusion-induced AKI was greater in C-reactive protein transgenics but was blunted when Smad3 was deleted. Exacerbation of AKI in C-reactive protein transgenics was associated with increased TGF-β/Smad3 signaling and expression of the cyclin kinase inhibitor p27, but decreased phosphorylated CDK2 and expression of cyclin E. Concomitantly, tubular epithelial cell proliferation was arrested at the G1 phase in C-reactive protein transgenics with fewer cells entering the S-phase cell cycle as evidenced by fewer bromodeoxyuridine-positive cells. In contrast, the protection from AKI in C-reactive protein transgenic/Smad3 knockout mice was associated with decreased expression of p27 and promotion of CDK2/cyclin E-dependent G1/S transition of tubular epithelial cells. In vitro studies using tubular epithelial cells showed that C-reactive protein activates Smad3 via both TGF-β-dependent and ERK/MAPK cross talk mechanisms, Smad3 bound directly to p27, and blockade of Smad3 or the Fc receptor CD32 prevented C-reactive protein-induced p27-dependent G1 cell cycle arrest. In vivo, treatment of C-reactive protein transgenics with a Smad3 inhibitor largely improved AKI outcomes. Thus, C-reactive protein may promote AKI by impairing tubular epithelial cell regeneration via the CD32-Smad3-p27-driven inhibition of the CDK2/cyclin E complex. Targeting Smad3 may offer a new treatment approach for AKI.

The non-genomic loss of function of tumor suppressors: an essential role in the pathogenesis of chronic myeloid leukemia chronic phase

BACKGROUND

Chronic Myeloid Leukemia was always referred as a unique cancer due to the apparent independence from tumor suppressors' deletions/mutations in the early stages of the disease. However, it is now well documented that even genetically wild-type tumor suppressors can be involved in tumorigenesis, when functionally inactivated. In particular, tumor suppressors' functions can be impaired by subtle variations of protein levels, changes in cellular compartmentalization and post-transcriptional/post-translational modifications, such as phosphorylation, acetylation, ubiquitination and sumoylation. Notably, tumor suppressors inactivation offers challenging therapeutic opportunities. The reactivation of an inactive and genetically wild-type tumor suppressor could indeed promote selective apoptosis of cancer cells without affecting normal cells.

MAIN BODY

Chronic Myeloid Leukemia (CML) could be considered as the paradigm for non-genomic loss of function of tumor suppressors due to the ability of BCR-ABL to directly promote functionally inactivation of several tumor suppressors.

SHORT CONCLUSION

In this review we will describe new insights on the role of FoxO, PP2A, p27, BLK, PTEN and other tumor suppressors in CML pathogenesis. Finally, we will describe strategies to promote tumor suppressors reactivation in CML.

Activation of AMPK inhibits PDGF-induced pulmonary arterial smooth muscle cells proliferation and its potential mechanisms

The aims of the present study were to examine signaling mechanisms for PDGF-induced pulmonary arterial smooth muscle cells (PASMC) proliferation and to determine the effect of AMPK activation on PDGF-induced PASMC proliferation and its underlying mechanisms. PDGF activated PI3K/Akt/mTOR signaling pathway, and this in turn up-regulated Skp2 and consequently reduced p27 leading to PASMC proliferation. Prior incubation of PASMC with metformin induced a dramatic AMPK activation and significantly blocked PDGF-induced cell proliferation. PASMC lacking AMPKα2 were resistant to the inhibitory effect of metformin on PDGF-induced cell proliferation. Metformin did not affect Akt activation but blocked mTOR phosphorylation in response to PDGF; these were accompanied by the reversion of Skp2 up-regulation and p27 reduction. Our study suggests that the activation of AMPK negatively regulates mTOR activity to suppress PASMC proliferation and therefore has a potential value in the prevention and treatment of pulmonary hypertension by negatively modulating pulmonary vascular remodeling.

New Insights Into the Mechanism of COP9 Signalosome-Cullin-RING Ubiquitin-Ligase Pathway Deregulation in Urological Cancers

Urological cancers are a very common type of cancer worldwide and have alarming high incidence and mortality rates, especially in kidney cancers, illustrate the urgent need for new therapeutic targets. Recent publications point to a deregulated COP9 signalosome (CSN)-cullin-RING ubiquitin-ligase (CRL) pathway which is here considered and investigated as potential target in urological cancers with strong focus on renal cell carcinomas (RCC). The CSN forms supercomplexes with CRLs in order to preserve protein homeostasis and was found deregulated in several cancer types. Examination of selected CSN-CRL pathway components in RCC patient samples and four RCC cell lines revealed an interesting deregulated p27(Kip1)-Skp2-CAND1 axis and two p27(Kip1) point mutations in 786-O cells; p27(Kip1)V109G and p27(Kip1)I119T. The p27(Kip1) mutants were detected in patients with RCC and appear to be responsible for an accelerated growth rate in 786-O cells. The occurrence of p27(Kip1)V109G and p27(Kip1)I119T in RCC makes the CSN-CRL pathway an attractive therapeutic target.

Adenosine Attenuates Human Coronary Artery Smooth Muscle Cell Proliferation by Inhibiting Multiple Signaling Pathways That Converge on Cyclin D

The goal of this study was to determine whether and how adenosine affects the proliferation of human coronary artery smooth muscle cells (HCASMCs). In HCASMCs, 2-chloroadenosine (stable adenosine analogue), but not N(6)-cyclopentyladenosine, CGS21680, or N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide, inhibited HCASMC proliferation (A2B receptor profile). 2-Chloroadenosine increased cAMP, reduced phosphorylation (activation) of ERK and Akt (protein kinases known to increase cyclin D expression and activity, respectively), and reduced levels of cyclin D1 (cyclin that promotes cell-cycle progression in G1). Moreover, 2-chloroadenosine inhibited expression of S-phase kinase-associated protein-2 (Skp2; promotes proteolysis of p27(Kip1)) and upregulated levels of p27(Kip1) (cell-cycle regulator that impairs cyclin D function). 2-Chloroadenosine also inhibited signaling downstream of cyclin D, including hyperphosphorylation of retinoblastoma protein and expression of cyclin A (S phase cyclin). Knockdown of A2B receptors prevented the effects of 2-chloroadenosine on ERK1/2, Akt, Skp2, p27(Kip1), cyclin D1, cyclin A, and proliferation. Likewise, inhibition of adenylyl cyclase and protein kinase A abrogated 2-chloroadenosine's inhibitory effects on Skp2 and stimulatory effects on p27(Kip1) and rescued HCASMCs from 2-chloroadenosine-mediated inhibition. Knockdown of p27(Kip1) also reversed the inhibitory effects of 2-chloroadenosine on HCASMC proliferation. In vivo, peri-arterial (rat carotid artery) 2-chloroadenosine (20 μmol/L for 7 days) downregulated vascular expression of Skp2, upregulated vascular expression of p27(Kip1), and reduced neointima hyperplasia by 71% (P<0.05; neointimal thickness: control, 37 424±18 371 pixels; treated, 10 352±2824 pixels). In conclusion, the adenosine/A2B receptor/cAMP/protein kinase A axis inhibits HCASMC proliferation by blocking multiple signaling pathways (ERK1/2, Akt, and Skp2) that converge at cyclin D, a key G1 cyclin that controls cell-cycle progression.

Gingerol Inhibits Serum-Induced Vascular Smooth Muscle Cell Proliferation and Injury-Induced Neointimal Hyperplasia by Suppressing p38 MAPK Activation

Purpose:

Gingerol inhibits growth of cancerous cells; however, its role in vascular smooth muscle cell (VSMC) proliferation is not known. The present study investigated the effect of gingerol on VSMC proliferation in cell culture and during neointima formation after balloon injury.

Method and Results:

Rat VSMCs or carotid arteries were harvested at 15 minutes, 30 minutes, 1, 6, 12, and 24 hours of fetal bovine serum (FBS; 10%) stimulation or balloon injury, respectively. Gingerol prevented FBS (10%)-induced proliferation of VSMCs in a dose-dependent manner (50 μmol/L-400 μmol/L). The FBS-induced proliferating cell nuclear antigen (PCNA) upregulation and p27Kip1 downregulation were also attenuated in gingerol (200 μmol/L) pretreated cells. Fetal bovine serum-induced p38 mitogen-activated protein kinase (MAPK) activation, PCNA upregulation, and p27Kip1 downregulation were abrogated in gingerol (200 μmol/L) and p38 MAPK inhibitor (SB203580, 10 μmol/L) pretreated cells. Balloon injury induced time-dependent p38 MAPK activation in the carotid artery. Pretreatment with gingerol (200 μmol/L) significantly attenuated injury-induced p38 MAPK activation, PCNA upregulation, and p27Kip1 downregulation. After 14 days of balloon injury, intimal thickening, neointimal proliferation, and endothelial dysfunction were significantly prevented in gingerol pretreated arteries. In isolated organ bath studies, gingerol (30 nmol/L-300 μmol/L) inhibited phenylephrine-induced contractions and induced dose-dependent relaxation of rat thoracic aortic rings in a partially endothelium-dependent manner.

Conclusion:

Gingerol prevented FBS-induced VSMC proliferation and balloon injury-induced neointima formation by regulating p38 MAPK. Vasodilator effect of gingerol observed in the thoracic aorta was partially endothelium dependent. Gingerol is thus proposed as an attractive agent for modulating VSMC proliferation, vascular reactivity, and progression of vascular proliferative diseases.