Tripeptidyl peptidase II in human oral squamous cell carcinoma

Mesenchymal stromal/stem cells promote intestinal epithelium regeneration after chemotherapy-induced damage

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for leukemia and a range of non-malignant disorders. The success of the therapy is hampered by occurrence of acute graft-versus-host disease (aGvHD); an inflammatory response damaging recipient organs, with gut, liver, and skin being the most susceptible. Intestinal GvHD injury is often a life-threatening complication in patients unresponsive to steroid treatment. Allogeneic mesenchymal stromal/stem cell (MSC) infusions are a promising potential treatment for steroid-resistant aGvHD. Data from our institution and others demonstrate rescue of approximately 40-50% of aGvHD patients with MSCs in Phase I, II studies and minor side effects. Although promising, better understanding of MSC mode of action and patient response to MSC-based therapy is essential to improve this lifesaving treatment.

METHODS

Single cell human small intestine organoids were embedded in Matrigel, grown for 5 days and treated with busulfan for 48 h. Organoids damaged by treatment with busulfan or control organoids were co-cultured with 5000, 10,000, and 50,000 MSCs for 24 h, 48 h or 7 days and the analyses such as surface area determination, proliferation and apoptosis assessment, RNA sequencing and proteomics were performed.

RESULTS

Here, we developed a 3D co-culture model of human small intestinal organoids and MSCs, which allows to study the regenerative effects of MSCs on intestinal epithelium in a more physiologically relevant setting than existing in vitro systems. Using this model we mimicked chemotherapy-mediated damage of the intestinal epithelium. The treatment with busulfan, the chemotherapeutic commonly used as conditioning regiment before the HSCT, affected pathways regulating epithelial to mesenchymal transition, proliferation, and apoptosis in small intestinal organoids, as shown by transcriptomic and proteomic analysis. The co-culture of busulfan-treated intestinal organoids with MSCs reversed the effects of busulfan on the transcriptome and proteome of intestinal epithelium, which we also confirmed by functional evaluation of proliferation and apoptosis.

CONCLUSIONS

Collectively, we demonstrate that our in vitro co-culture system is a new valuable tool to facilitate the investigation of the molecular mechanisms behind the therapeutic effects of MSCs on damaged intestinal epithelium. This could benefit further optimization of the use of MSCs in HSCT patients.

Linking TPPII to the protein interaction and signalling networks

Tripeptidyl peptidase II (TPPII) is primarily considered a house-keeping exopeptidase, which contributes to the functions of the ubiquitin-proteasome system by the maintenance of the cellular amino acid homeostasis. Although functionally well-characterised in vitro and using the mammalian cell models, less is known about the molecular mechanisms of its involvement in the signalling and metabolic pathways, which mediate its cellular functions. The present protein-protein interaction network analysis identified these mechanisms involved in the adaptive and innate immunity, the metabolism of the glucose, cancer cell growth, apoptosis, cell cycle and DNA damage responses. The interaction network constructed based on the publicly available protein-protein interaction data was extended by the application GeneMania, which was further used for the pathway enrichment, the protein function prediction and the protein node prioritisation analysis. The analysis suggested that the molecular mechanisms linked to the adaptive and innate immunity (ID, Kit receptor, BCR, IL-2 and G-CSF signalling; the regulation of NFκB), the aerobic glycolysis (ID and IL-2 signalling), tumorigenesis (TGF-β and p53 signalling; the top priority nodes MAPKs, mTOR regulation), diabetes (Kit receptor signalling; the top priority node GSK3β) and neurodegeneration (the control of mTOR and Aβ peptide degradation) are controlling the resulting TPPII interaction network. The uncharacterized interactions with two lung cancer suppressors (DOK3, DENND2D), a protein involved in the increased risk of the lung cancer in smokers (CYP1A1) and a protein implicated in asthmatic reactions (CHIA) suggest potential roles of TPPII in the lung cancer pathology. The interactions with methyltransferase CARNMT1, which modifies di- and tripeptides and the xenobiotic processing enzyme CYP1A1, are additional candidates for the breakthrough in new functions discovery of TPPII.

SYT12 plays a critical role in oral cancer and may be a novel therapeutic target

Synaptotagmin12 (SYT12) has been well characterized as the regulator of transmitter release in the nervous system, however the relevance and molecular mechanisms of SYT12 in oral squamous cell carcinoma (OSCC) are not understood. In the current study, we investigated the expression of SYT12 and its molecular biological functions in OSCC by quantitative reverse transcriptase polymerase chain reaction, immunoblot analysis, and immunohistochemistry. SYT12 were up-regulated significantly in OSCC-derived cell lines and primary OSCC tissue compared with the normal counterparts (P<0.05) and the SYT12 expression levels were correlated significantly with clinical indicators, such as the primary tumoral size, lymph node metastasis, and TNM stage (P<0.05). SYT12 knockdown OSCC cells showed depressed cellular proliferation, migration, and invasion with cell cycle arrest at G1 phase. Surprisingly, we found increased calcium/calmodulin-dependent protein kinase 2 (CAMK2) inhibitor 1 (CAMK2N1) and decreased CAMK2-phosphorylation in the knockdown cells. Furthermore, treatment with L-3, 4-dihydroxyphenylalanine (L-dopa), a drug approved for Parkinson's disease, led to down-regulation of SYT12 and similar phenotypes to SYT12 knockdown cells. Taken together, we concluded that SYT12 plays a significant role in OSCC progression via CAMK2N1 and CAMK2, and that L-dopa would be a new drug for OSCC treatment through the SYT12 expression.

Centromere Protein N Participates in Cellular Proliferation of Human Oral Cancer by Cell-Cycle Enhancement

Centromere protein N (CENP-N), an important member of the centromere protein family, is essential for kinetochore assembly and chromosome segregation; however, the relevance of CENP-N in cancers remains unknown. The aim of this study was to investigate CENP-N expression and its functional mechanisms in oral squamous cell carcinoma (OSCC). CENP-N expression was up-regulated significantly in vitro and in vivo in OSCCs. Overexpressed CENP-N was closely (p < 0.05) correlated with tumor growth using quantitative reverse transcriptase-polymerase chain reaction, immunoblot analysis, and immunohistochemistry. CENP-N knockdown (shCENP-N) cells showed depressed cellular proliferation by cell-cycle arrest at the G1 phase with up-regulation of p21^Cip1 and p27^Kip1 and down-regulation of cyclin D1, CDK2, and CDK4. Interestingly, we newly discovered that calcitriol (1, 25-dihydroxyvitamin D3) controlled the CENP-N expression level, leading to inhibition of tumor growth similar to shCENP-N cells. These results suggested that CENP-N plays a critical role in determining proliferation of OSCCs and that calcitriol might be a novel therapeutic drug for OSCCs by regulating CENP-N.

UNC93B1 promotes tumoral growth by controlling the secretion level of granulocyte macrophage colony-stimulating factor in human oral cancer

Unc-93 homolog B1 (UNC93B1), a transmembrane protein, is correlated with immune diseases, such as influenza, herpes simplex encephalitis, and the pathogenesis of systemic lupus erythematosus; however, the role of UNC93B1 in cancers including human oral squamous cell carcinomas (OSCCs) remains unknown. In the current study, we investigated the UNC93B1expression level in OSCCs using quantitative reverse transcription-polymerase chain reaction, immunoblot analysis, and immunohistochemistry. Our data showed that UNC93B1 mRNA and protein expressions increased markedly (p < 0.05) in OSCCs compared with normal cells and tissues and that high expression of UNC93B1 in OSCCs was related closely to tumoral size. UNC93B1 knockdown (shUNC93B1) OSCC cells showed decreased cellular proliferation by cell-cycle arrest in the G1 phase with up-regulation of p21^Cip1 and down-regulation of CDK4, CDK6, cyclin D1, and cyclin E. We also found that granulocyte macrophage colony-stimulating factor (GM-CSF) was down-regulated significantly (p < 0.05) in shUNC93B1 OSCC cells. Moreover, inactivation of GM-CSF using neutralization antibody led to cell-cycle arrest at the G1 phase similar to the phenotype of the shUNC93B1 cells. The current findings indicated that UNC93B1 might play a crucial role in OSCC by controlling the secretion level of GM-CSF involved in tumoral growth and could be a potential therapeutic target for OSCCs.

Increased expression of tripartite motif (TRIM) like 2 promotes tumoral growth in human oral cancer

Tripartite motif family-like 2 (TRIML2), a member of the TRIM proteins family, is closely related to Alzheimer's disease, however, no studies of TRIML2 have been published in the cancer research literature. In the current study, we investigated the expression level of TRIML2 and its molecular mechanisms in human oral squamous cell carcinoma (OSCC); reverse transcriptase-quantitative polymerase chain reaction, immunoblot analysis, and immunohistochemistry showed that TRIML2 is up-regulated significantly in OSCCs in vitro and in vivo. TRIML2 knockdown OSCC cells showed decreased cellular proliferation by cell-cycle arrest at G1 phase that resulted from down-regulation of CDK4, CDK6, and cyclin D1 and up-regulation of p21^Cip1 and p27^Kip1. Surprisingly, resveratrol, a polyphenol, led to not only down-regulation of TRIML2 but also cell-cycle arrest at G1 phase similar to TRIML2 knockdown experiments. Taken together, we concluded that TRIML2 might play a significant role in tumoral growth and that resveratrol may be a new drug for treating OSCC by interfering with TRIML2 function.

Diacylglycerol lipase alpha promotes tumorigenesis in oral cancer by cell-cycle progression

Diacylglycerol lipase alpha (DAGLA), which catalyzes the hydrolysis of diacylglycerol to 2-arachidonoylglycerol and free fatty acid, is required for axonal growth during the brain development and for retrograde synaptic signaling at mature synapses. So far, no information was found regarding the possible role of DAGLA in human tumorigenesis. Thus, the current study sought to clarify the contribution of DAGLA in oral squamous cell carcinomas (OSCCs) and assess the clinical possibilities for OSCC treatment. Using real-time quantitative reverse transcription-polymerase chain reaction, immunoblotting, and immunohistochemistry, we found a significant up-regulation of DAGLA in OSCCs compared with normal cells and tissues both at mRNA and protein expression levels. Knockdown models in OSCC-derived cell lines for DAGLA (siDAGLA) and treatment with a lipase inhibitor (orlistat) showed several depressed cellular functions, including cellular proliferation and migratory activities through cell-cycle arrest at G1 phase. Furthermore, we found that DAGLA-positive OSCC samples were correlated highly with the primary tumoral size. We concluded that DAGLA may be a key determinant in tumoral progression and might be a therapeutic target for OSCCs.

Evaluation of tryptophan-aspartic acid repeat-containing protein 34 as a novel tumor-suppressor molecule in human oral cancer

Tryptophan-aspartic acid (WD) repeat-containing protein 34 (WDR34), one of the WDR protein superfamilies with five WD40 domains, inhibits a transforming growth factor-beta (TGF-β) activated kinase 1 (TAK1)-associated NF-κB activation pathway. Nevertheless, little is known about the roles of WDR34 in cancer. The current study sought to elucidate the clinical relevance of WDRsfb34 in oral squamous cell carcinoma (OSCC). We found WDR34 down-regulation in OSCCs compared with normal control tissues using real-time quantitative reverse transcription-polymerase chain reaction, immunoblotting, and immunohistochemistry. Models of overexpression of WDR34 (oeWDR34) showed depressed cellular growth through cell-cycle arrest at the G1 phase. To investigate the inhibitory function of WDR34, we challenged oeWDR34 cells with interleukin (IL)-1, a ligand for activation of the TAK1-NF-κB pathway and assessed the expression of a target gene of the pathway. oeWDR34 strongly inhibited IL-6 expression, which is closely related to tumoral growth, compared with control cells, suggesting that WDR34 would be a critical molecule for control of tumoral progression. In addition to the in vitro experiments, WDR34 negativity was correlated with tumoral growth of OSCCs. Our findings suggested that WDR34 inhibits OSCC progression and might be a potential tumor-suppressor molecule in OSCCs.

Activin B Regulates Adhesion, Invasiveness, and Migratory Activities in Oral Cancer: a Potential Biomarker for Metastasis

Activin B, a homodimer of inhibin beta b (INHBB), is a multifunctional cytokine belonging to the transforming growth factor-β (TGF-β) family. However, the molecular functions and clinical relevance of activin B have not been determined in oral cancer. We investigated the critical roles of activin B in oral squamous cell carcinoma (OSCC). We performed quantitative reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry to study INHBB expression in OSCC-derived cell lines and OSCC clinical samples. The INHBB expression levels were significantly (P < 0.05) overexpressed in OSCCs compared to normal counterparts in vitro and in vivo. Activin B-positivity in OSCC cases was significantly (P < 0.05) correlated with regional lymph node metastasis. The INHBB knockdown (shINHBB) cells promoted cellular adhesion and suppression of cellular invasiveness and migration. After treatment of shINHBB cells with activin B, those activities were restored similar to the shMock cells. In the processes of invasiveness and metastasis, the cells cause epithelial-mesenchymal transition (EMT). TGF-β and its family members are promoters of the EMT process. To investigate whether activin B is related to EMT, we examined the expressions of EMT-related genes and found that INHBB was related closely to EMT. Our results suggested for the first time that activin B indicates tumoral metastasis in OSCCs and might be a useful biomarker for OSCC metastasis.

UBE2S associated with OSCC proliferation by promotion of P21 degradation via the ubiquitin-proteasome system

Ubiquitin-conjugating enzyme E2S (UBE2S), a family of E2 protein in the ubiquitin-proteasome system, is highly expressed in several types of cancers; however, its roles in oral squamous cell carcinoma (OSCC) have not yet been well elucidated. The purpose of this study was to clarify the functional activities of UBE2S in OSCCs. We analyzed the expression levels of UBE2S in nine OSCC cell lines and primary OSCC tissues by quantitative reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry (IHC). The correlations between UBE2S expression and clinical classifications of OSCCs were analyzed using the IHC scoring system. We also used UBE2S knockdown OSCC cells for functional assays (proliferation assay, flow cytometry, and Western blotting). UBE2S was overexpressed in OSCCs in vitro and in vivo and was correlated significantly (P < 0.05) with the primary tumoral size. The cellular growth was decreased and the cell-cycle was arrested in the G2/M phase in the UBE2S knockdown (shUBE2S) cells. The expression level of P21, a target of the ubiquitin-proteasome system, was increased in the shUBE2S cells because of lower anaphase activity that promotes complex subunit 3 (APC3), an E3 ubiquitin ligase, compared with shMock cells. These findings might promote the understanding of the relationship between UBE2S overexpression and oral cancer proliferation, indicating that UBE2S would be a potential biomarker of and therapeutic target in OSCCs.

Evidence for Critical Role of Lymphocyte Cytosolic Protein 1 in Oral Cancer

Lymphocyte cytosolic protein 1 (LCP1), a member of actin-binding protein of the plastin family, has been identified in several malignant tumors of non-hematopoietic sites, such as the colon, prostate, and breast. However, little is known about the roles of LCP1 in oral squamous cell carcinomas (OSCCs). This present study sought to clarify the clinical relevance of LCP1 in OSCCs and investigate possible clinical applications for treating OSCCs by regulating LCP1 expression. We found up-regulation of LCP1in OSCCs compared with normal counterparts using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunoblotting, and immunohistochemistry (P < 0.05). We used shRNA models for LCP1 (shLCP1) and enoxacin (ENX), a fluoroquinolone antibiotic drug, as a regulator of LCP1 expression. In addition to the LCP1 knockdown experiments in which shLCP1 cells showed several depressed functions, including cellular proliferation, invasiveness, and migratory activities, ENX-treated cells also had attenuated functions. Consistent with our hypothesis from our in vitro data, LCP1-positive OSCC samples were correlated closely with the primary tumoral size and regional lymph node metastasis. These results suggested that LCP1 is a useful biomarker for determining progression of OSCCs and that ENX might be a new therapeutic agent for treating OSCCs by controlling LCP1 expression.

Role of tripeptidyl peptidase II in MHC class I antigen presentation: Biological characteristics, cellular crosstalk and signaling

Tripeptidyl peptidase II (TPPII) is a multifunctional cytoplasmic serine protease. The main function of TPPII is to cleave proteasome-generated peptides into tripeptides, which can then be further degraded into free amino acids. Recent evidence suggests that TPPII plays an important role in epitope generation, but the mechanisms of TPPII in MHC class I antigen presentation remain unclear. Recent research has shed new light on the mechanisms and functions of TPPII in MHC class I antigen presentation. We therefore provide an updated review of the biological characteristics of TPPII and explore its role in MHC class I antigen presentation.

ARNT2 Regulates Tumoral Growth in Oral Squamous Cell Carcinoma

Aryl hydrocarbon receptor nuclear translocator (ARNT) 2 is a transcriptional factor related to adaptive responses against cellular stress from a xenobiotic substance. Recent evidence indicates ARNT is involved in carcinogenesis and cancer progression; however, little is known about the relevance of ARNT2 in the behavior of oral squamous cell carcinoma (OSCC). In the current study, we evaluated the ARNT2 mRNA and protein expression levels in OSCC in vitro and in vivo and the clinical relationship between ARNT2 expression levels in primary OSCCs and their clinicopathologic status by quantitative reverse transcriptase-polymerase chain reaction, immunoblotting, and immunohistochemistry. Using ARNT2 overexpression models, we performed functional analyses to investigate the critical roles of ARNT2 in OSCC. ARNT2 mRNA and protein were down-regulated significantly (P < 0.05 for both comparisons) in nine OSCC-derived cells and primary OSCC (n=100 patients) compared with normal counterparts. In addition to the data from exogenous experiments that ARNT2-overexpressed cells showed decreased cellular proliferation, ARNT2-positive OSCC cases were correlated significantly (P < 0.05) with tumoral size. Since von Hippel-Lindau tumor suppressor, E3 ubiquitin protein ligase, a negative regulator of hypoxia-inducible factor (HIF1)-α, is a downstream molecule of ARNT2, we speculated that HIF1-α and its downstream molecules would have key functions in cellular growth. Consistent with our hypothesis, overexpressed ARNT2 cells showed down-regulation of HIF1-α, which causes hypofunctioning of glucose transporter 1, leading to decreased cellular growth. Our results proposed for the first time that the ARNT2 level is an indicator of cellular proliferation in OSCCs. Therefore, ARNT2 may be a potential therapeutic target against progression of OSCCs.

Kinesin family member 14 in human oral cancer: A potential biomarker for tumoral growth

Kinesin family member 14 (KIF14), a microtubule-based motor protein, plays an important role in chromosomal segregation, congression, and alignment. Considerable evidence indicates that KIF14 is involved in cytokinesis, although little is known about its role in oral squamous cell carcinomas (OSCCs). In the current study, we functionally and clinically investigated KIF14 expression in patients with OSCC. Quantitative reverse transcriptase–polymerase chain reaction and immunoblotting analyses were used to assess the KIF14 regulatory mechanism in OSCC. Immunohistochemistry (IHC) was performed to analyze the correlation between KIF14 expression and clinical behavior in 104 patients with OSCC. A KIF14 knockdown model of OSCC cells (shKIF14 cells) was used for functional experiments. KIF14 expression was up-regulated significantly (P<0.05) in OSCCs compared with normal counterparts in vitro and in vivo. In addition, shKIF14 cells inhibited cellular proliferation compared with control cells by cell-cycle arrest at the G2/M phase through up-regulation of G2 arrest-related proteins (p-Cdc2 and cyclin B1). As expected, IHC data from primary OSCCs showed that KIF14-positive patients exhibited significantly (P<0.05) more larger tumors compared with KIF14-negative patients. The current results suggest for the first time that KIF14 is an indicator of tumoral size in OSCCs and that KIF14 might be a potential therapeutic target for development of new treatments for OSCCs.

Tripeptidyl Peptidase II Mediates Levels of Nuclear Phosphorylated ERK1 and ERK2

Tripeptidyl peptidase II (TPP2) is a serine peptidase involved in various biological processes, including antigen processing, cell growth, DNA repair, and neuropeptide mediated signaling. The underlying mechanisms of how a peptidase can influence this multitude of processes still remain unknown. We identified rapid proteomic changes in neuroblastoma cells following selective TPP2 inhibition using the known reversible inhibitor butabindide, as well as a new, more potent, and irreversible peptide phosphonate inhibitor. Our data show that TPP2 inhibition indirectly but rapidly decreases the levels of active, di-phosphorylated extracellular signal-regulated kinase 1 (ERK1) and ERK2 in the nucleus, thereby down-regulating signal transduction downstream of growth factors and mitogenic stimuli. We conclude that TPP2 mediates many important cellular functions by controlling ERK1 and ERK2 phosphorylation. For instance, we show that TPP2 inhibition of neurons in the hippocampus leads to an excessive strengthening of synapses, indicating that TPP2 activity is crucial for normal brain function.

WWP2 is overexpressed in human oral cancer, determining tumor size and poor prognosis in patients: downregulation of WWP2 inhibits the AKT signaling and tumor growth in mice

The WW domain containing E3 ubiquitin protein ligase 2 (WWP2) encodes a member of the Nedd4 family of E3 ligases, which catalyzes the final step of the ubiquitination cascade. WWP2 is involved in tumoral growth with degradation of the tumor suppressor phosphatase and tensin homologue deleted on chromosome TEN (PTEN). However, little is known about the mechanisms and roles of WWP2 in human malignancies including oral squamous cell carcinomas (OSCCs). We found frequent WWP2 overexpression in all OSCC-derived cell lines examined that was associated with cellular growth by accelerating the cell cycle in the G1 phase via degradation of PTEN and activation of the PI3K/AKT signaling pathway. Our in vivo data of WWP2 silencing showed dramatic inhibition of tumoral growth with increased expression of PTEN. Our 104 primary OSCCs had significantly higher expression of WWP2 than their normal counterparts. Moreover, among the clinical variables analyzed, enhanced WWP2 expression was correlated with primary tumoral size and poor prognosis. These data suggested that WWP2 overexpression contributes to neoplastic promotion via the PTEN/PI3K/AKT pathway in OSCCs. WWP2 is likely to be a biomarker of tumoral progression and prognosis and a potential therapeutic target for development of anticancer drugs in OSCCs.

Kinesin family member 4A: a potential predictor for progression of human oral cancer

BACKGROUND

Kinesin family member 4A (KIF4A), a microtubule-based motor protein, was implicated in regulation of chromosomal structure and kinetochore microtubule dynamics. Considering the functions of KIF4A, we assumed that KIF4A is involved in progression of oral squamous cell carcinomas (OSCCs) via activation of the spindle assembly checkpoint (SAC). However, little is known about the relevance of KIF4A in the behavior of OSCC. We investigated the KIF4A expression status and its functional mechanisms in OSCC.

METHODS

The KIF4A expression levels in seven OSCC-derived cells were analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Using a KIF4A knockdown model, we assessed the expression of (SAC)-related molecules (BUB1, MAD2, CDC20, and cyclin B1), cell-cycle, and cellular proliferation. In addition to in vitro data, the clinical correlation between the KIF4A expression levels in primary OSCCs (n = 106 patients) and the clinicopathologic status by immunohistochemistry (IHC) also were evaluated.

RESULTS

KIF4A mRNA and protein were up-regulated significantly (P < 0.05) in seven OSCC-derived cells compared with human normal oral keratinocytes. In the KIF4A knockdown cells, SAC activation was observed via increased BUB1 expression on the kinetochores, appropriate kinetochore localization of MAD2, down-regulation of CDC20, up-regulation of cyclin B1, and cell-cycle arrested at G2/M phase. The results showed that cellular proliferation of KIF4A knockdown cells decreased significantly (P < 0.05) compared with control cells. IHC showed that KIF4A expression in primary OSCCs was significantly (P < 0.05) greater than in the normal oral counterparts and that KIF4A-positive OSCCs were correlated closely (P < 0.05) with tumoral size.

CONCLUSIONS

Our results proposed for the first time that KIF4A controls cellular proliferation via SAC activation. Therefore, KIF4A might be a key regulator for tumoral progression in OSCCs.