Transcription factor HBP1 is a direct anti-cancer target of transcription factor FOXO1 in invasive oral cancer

A Comprehensive Review of Natural Products as Therapeutic or Chemopreventive Agents against Head and Neck Squamous Cell Carcinoma Cells Using Preclinical Models

Head and neck squamous cell carcinoma (HNSCC) is a type of cancer that arises from the epithelium lining of the oral cavity, hypopharynx, oropharynx, and larynx. Despite the advancement of current treatments, including surgery, chemotherapy, and radiotherapy, the overall survival rate of patients afflicted with HNSCC remains poor. The reasons for these poor outcomes are due to late diagnoses and patient-acquired resistance to treatment. Natural products have been extensively explored as a safer and more acceptable alternative therapy to the current treatments, with numerous studies displaying their potential against HNSCC. This review highlights preclinical studies in the past 5 years involving natural products against HNSCC and explores the signaling pathways altered by these products. This review also addresses challenges and future directions of natural products as chemotherapeutic and chemoprevention agents against HNSCC.

FOXO1: a pivotal pioneer factor in oral squamous cell carcinoma

The transcription factor FOXO1 regulates cell cycle progression, apoptosis and oxidative stress. Interestingly, numerous studies have implicated their positive role in tumor suppression, angiogenesis and metastasis in oral squamous cell carcinoma (OSCC). Distinct post-transcriptional and post-translational modifications actuate the physiological role of FOXO1 in OSCC. Here, we evaluate the role of FOXO1 proteins in OSCC, their fundamental structure and the major players involved in FOXO1 regulation and how they are Pharmacologically modulated in OSCC. Finally, their role in regulating epithelial-mesenchymal transition (EMT), autophagy, stress tolerance and stemness, which would significantly aid in novel potential oversight for future research and thus developing strategies to prevent or reverse OSCC.

Molecular Screening for Nigericin Treatment in Pancreatic Cancer by High-Throughput RNA Sequencing

Objectives: Nigericin, an antibiotic derived from Streptomyces hygroscopicus, has been proved to exhibit promising anti-cancer effects on a variety of cancers. Our previous study investigated the potential anti-cancer properties in pancreatic cancer (PC), and demonstrated that nigericin could inhibit the cell viabilities in concentration- and time-dependent manners via differentially expressed circular RNAs (circRNAs). However, the knowledge of nigericin associated with long non-coding RNA (lncRNA) and mRNA in pancreatic cancer (PC) has not been studied. This study is to elucidate the underlying mechanism from the perspective of lncRNA and mRNA.

Methods: The continuously varying molecules (lncRNAs and mRNAs) were comprehensively screened by high-throughput RNA sequencing.

Results: Our data showed that 76 lncRNAs and 172 mRNAs were common differentially expressed in the nigericin anti-cancer process. Subsequently, the bioinformatics analyses, including Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, coding and non-coding co-expression network, cis- and trans-regulation predictions and protein-protein interaction (PPI) network, were applied to annotate the potential regulatory mechanisms among these coding and non-coding RNAs during the nigericin anti-cancer process.

Conclusions: These findings provided new insight into the molecular mechanism of nigericin toward cancer cells, and suggested a possible clinical application in PC.

Regulatory role of transcription factor HBP1 in anticancer efficacy of EGFR inhibitor erlotinib in HNSCC

BACKGROUND

Epidermal growth factor receptor (EGFR) is often hyperactivated in head and neck squamous cell carcinoma (HNSCC); however, its downstream mediators are not fully identified. Here, we investigate the role of transcription factor HBP1 in the anticancer efficacy of EGFR inhibitor erlotinib in HNSCC.

METHODS

The effect of erlotinib and HBP1 on cell proliferation and invasion was examined by flow cytometric analysis and a Matrigel invasion assay, respectively. Oral tumor specimens were used to evaluate the association between the expression level of EGFR and HBP1, and metastatic potential.

RESULTS

Erlotinib caused cell growth arrest in the G1 phase and sluggish invasion with a concomitant increase in HBP1 and p27 expression. The erlotinib effect was attenuated upon HBP1 knockdown. Analysis of oral tumor specimens revealed that the low HBP1/high EGFR status can predict metastatic potential.

CONCLUSIONS

Our data support HBP1 as a crucial mediator of EGFR-targeting inhibitors in HNSCC.

KCTD12 promotes G1/S transition of breast cancer cell through activating the AKT/FOXO1 signaling

Background

Sustaining proliferation is the most fundamental step for breast cancer tumor genesis. Accelerated proliferation is usually linked to the uncontrolled cell cycle. However, the internal and external factors linked to the activation of breast cancer cell cycle are still to be investigated.

Methods

quantitative PCR (qPCR) and Western blotting assay were used to detect the expression of potassium channel tetramerization domain containing 12 (KCTD12) in breast cancer. MTT and colony formation assays were performed to evaluate the effect of KCTD12 on cell proliferation of breast cancer. Anchorage‐independent growth assay was used to examine the in vitro tumorigenesis of breast cancer cells. Flow cytometry assay, qPCR, and Western blotting were used to investigate the detailed mechanisms of KCTD12 on breast cancer progression.

Results

Herein, the result showed that the level of KCTD12 is significantly decreased in breast cancer tissues and cells, and lower level of KCTD12 predicts poorer survival for patients with breast cancer. Further cell function tests illustrated that downregulation of KCTD12 significantly promotes cell proliferation and in vitro tumor genesis. Besides, molecular biologic experiments showed that downregulation of KCTD12 can enhance the G1/S transition through activating the AKT/FOXO1 signaling.

Conclusion

Our study inferred that downregulation of KCTD12 can be a novel factor for poor prognosis in breast cancer.

Transient FOXO1 inhibition in pancreatic endoderm promotes the generation of NGN3+ endocrine precursors from human iPSCs

In the multi-step differentiation protocol used to generate pancreatic endocrine cells from human pluripotent stem cells, the induction of NGN3+ endocrine precursors from the PDX1+/NKX6.1+ pancreatic endoderm is crucial for efficient endocrine cell production. Here, we demonstrate that transient, not prolonged FOXO1 inhibition results in enhanced NGN3+ endocrine precursors and hormone-producing cell production. FOXO1 inhibition does not directly induce NGN3 expression but stimulates PDX1+/NKX6.1+ cell proliferation. NOTCH activity, whose suppression is important for Ngn3 expression, is not suppressed but Wnt signaling is stimulated by FOXO1 inhibition. Reversely, Wnt inhibition suppresses the effects of FOXO1 inhibitor. These findings indicate that FOXO1 and Wnt are involved in regulating the proliferation of PDX1+/NKX6.1+ pancreatic endoderm that gives rise to NGN3+ endocrine precursors.

The HMG box transcription factor HBP1: a cell cycle inhibitor at the crossroads of cancer signaling pathways

HMG box protein 1 (HBP1) is a transcription factor and a potent cell cycle inhibitor in normal and cancer cells. HBP1 activates or represses the expression of different cell cycle genes (such as CDKN2A, CDKN1A, and CCND1) through direct DNA binding, cofactor recruitment, chromatin remodeling, or neutralization of other transcription factors. Among these are LEF1, TCF4, and MYC in the WNT/beta-catenin pathway. HBP1 also contributes to oncogenic RAS-induced senescence and terminal cell differentiation. Collectively, these activities suggest a tumor suppressor function. However, HBP1 is not listed among frequently mutated cancer driver genes. Nevertheless, HBP1 expression is lower in several tumor types relative to matched normal tissues. Several micro-RNAs, such as miR-155, miR-17-92, and miR-29a, dampen HBP1 expression in cancer cells of various origins. The phosphatidylinositol-3 kinase (PI3K)/AKT pathway also inhibits HBP1 transcription by preventing FOXO binding to the HBP1 promoter. In addition, AKT directly phosphorylates HBP1, thereby inhibiting its transcriptional activity. Taken together, these findings place HBP1 at the center of a network of micro-RNAs and oncoproteins that control cell proliferation. In this review, we discuss our current understanding of HBP1 function in human physiology and diseases.

Glioma exosomes mediate the expansion and function of myeloid-derived suppressor cells through microRNA-29a/Hbp1 and microRNA-92a/Prkar1a pathways

Myeloid-derived suppressor cells (MDSCs) play a pivotal role in mediating the formation of an immunosuppressive environment and assisting tumors in evading the host immune response. However, the mechanism through which tumors manipulate the differentiation and function of MDSCs remains unclear. Here, we report that hypoxia-induced glioma cells can stimulate the differentiation of functional MDSCs by transferring exosomal miR-29a and miR-92a to MDSCs. Our results showed that glioma-derived exosomes (GEXs) can enhance the differentiation of functional MDSCs both in vitro and in vivo, and hypoxia-induced GEXs (H-GEXs) demonstrated a stronger MDSCs induction ability than did normoxia-induced GEXs (N-GEXs). A subsequent miRNA sequencing analysis of N-GEXs and H-GEXs revealed that hypoxia-induced exosomal miR-29a and miR-92a expression induced the propagation of MDSCs. miR-29a and miR-92a activated the proliferation and function of MDSCs by targeting high-mobility group box transcription factor 1 (Hbp1) and protein kinase cAMP-dependent type I regulatory subunit alpha (Prkar1a), respectively. Altogether, the results of our study provide new insights into the role of glioma exosomal miRNAs in mediating the formation of immunosuppressive microenvironments in tumors and elucidate the underlying exosomal miR-29a/miR-92a-based regulatory mechanism responsible for the modulation of functional MDSC induction.

Matrix metalloproteinase-13 is a target gene of high-mobility group box-containing protein 1 in modulating oral cancer cell invasion

Transcription factor high-mobility group box-containing protein 1 (HBP1) may function as a tumor suppressor in various types of cancer. In a previous study, we demonstrated that HBP1 suppressed cell invasion in oral cancer. To further understand the underlying mechanism, the current study is aimed at investigating how HBP1 exerts its antimetastatic potential in oral cancer. In a cell model, ectopic expression of HBP1 potently suppressed epithelial-mesenchymal transition, cellular migration, and invasion; conversely, HBP1 knockdown promoted these malignant phenotypes. The matrix metalloproteinase (MMP) family is highly implicated in tumor metastasis. Therefore, we examined the effect of HBP1 on the activation of the MMP members, MMP-2, -9, and -13 that are highly associated with the aggressiveness of oral cancer. Ectopic expression of HBP1 resulted in a mild reduction in the expression and activity of MMP-2 and -9, yet it had a potent inhibitory effect on MMP-13. In contrast, HBP1 knockdown strongly enhanced the activation of MMP-13. Further, we demonstrated that MMP-13 is a target of HBP1 transcription repression as evidenced by the identification of an HBP1 binding site in the cis proximal region of the MMP-13 promoter. More important, MMP-13 knockdown significantly alleviated HBP1 small interfering RNA-mediated promotion in cell invasion. Analysis of oral tumor specimens revealed that the low HBP1 (<0.3-fold)/high MMP-13 (>3-fold) status was associated with metastatic potential. All told, our study provides evidence supporting the idea that the HBP1-MMP-13 axis is a key regulator of the aggressiveness in oral cancer.

MiR-21 improves invasion and migration of drug-resistant lung adenocarcinoma cancer cell and transformation of EMT through targeting HBP1

This study was aimed at the investigation of the effects of miR-21 on drug resistance, invasion, migration, and epithelial-mesenchymal transition (EMT) of lung adenocarcinoma cells and the related molecular mechanisms. Cell viability of A549 cell line was measured by MTT assay. Wound healing assay and transwell assay were, respectively, employed to examine cell migration and invasion abilities. The cells were transfected with miR-21 mimic or inhibitor using Lipofectamine 3000. The target relationship between miR-21 and HBP1 was confirmed by luciferase reporter gene assay. Western blot and qRT-PCR were used to examine the expression of HBP1 and EMT-related molecules. Compared with A549 cells, drug resistance of A549/PTX cells and A549/DDP cells were obviously stronger. A549/PTX cells and A549/DDP cells had stronger ability of migration and invasion compared with parental A549 cells. Meanwhile, EMT of A549/PTX and A549/DDP was significantly higher than that of A549 cells. MiR-21 promoted migration, invasion, and EMT of human lung adenocarcinoma cancer cells. Our experiment also verified the target relationship between miR-21 and HBP1. MiR-21 may affect migration and invasion ability of drug-resistant lung adenocarcinoma cells by targeting HBP1, therefore modulating EMT.

HBP1 phosphorylation by AKT regulates its transcriptional activity and glioblastoma cell proliferation

The HMG-box protein 1 (HBP1) is a transcriptional regulator and a potential tumor suppressor that controls cell proliferation, differentiation and oncogene-mediated senescence. In a previous study, we showed that AKT activation through the PI3K/AKT/FOXO pathway represses HBP1 expression at the transcriptional level in human fibroblasts as well as in cancer cell lines. In the present study, we investigated whether AKT could also regulate HBP1 directly. First, AKT1 phosphorylated recombinant human HBP1 in vitro on three conserved sites, Ser380, Thr484 and Ser509. In living cells, we confirmed the phosphorylation of HBP1 on residues 380 and 509 using phospho-specific antibodies. HBP1 phosphorylation was induced by growth factors, such as EGF or IGF-1, which activated AKT. Conversely, it was blocked by treatment of cells with an AKT inhibitor (MK-2206) or by AKT knockdown. Next, we observed that HBP1 transcriptional activity was strongly modified by mutating its phosphorylation sites. The regulation of target genes such as DNMT1, P47phox, p16^INK4A and cyclin D1 was also affected. HBP1 had previously been shown to limit glioma cell growth. Accordingly, HBP1 silencing by small-hairpin RNA increased human glioblastoma cell proliferation. Conversely, HBP1 overexpression decreased cell growth and foci formation. This effect was amplified by mutations that prevented phosphorylation by AKT, and blunted by mutations that mimicked phosphorylation. In conclusion, our results suggest that HBP1 phosphorylation by AKT blocks its functions as transcriptional regulator and tumor suppressor.