Role of JNK signaling in oral cancer: A mini review

JNKs (c-Jun N-terminal kinases) belong to mitogen-activated protein kinases’ family and become activated by several growth factors, stress, radiation, and other extracellular signals. In turn, JNK activation results in phosphorylation of downstream molecules involved in many normal cellular processes. Nevertheless, recent data have linked JNK signaling with several pathological conditions, including neurodegenerative diseases, inflammation, and cancer. The role of JNK in cancer remains controversial. Initially, JNK was thought to play a rather oncosuppressive role by mediating apoptosis in response to stress stimuli, inflammatory, or oncogenic signals. However, a number of studies have implicated JNK in malignant transformation and tumor growth. The contradictory functions of JNK in cancer may be due to the diversity of JNK upstream and downstream signaling and are under intensive investigation. This review summarizes current literature focusing on the significance of JNK pathway in cancer development and progression, particularly addressing its role in oral cancer. Understanding the complexity of JNK signaling has the potential to elucidate important molecular aspects of oral cancer, possibly leading to development of novel and individualized therapeutic strategies. © The Author(s) 2017

p38 Expression and Modulation of STAT3 Signaling in Oral Cancer

p38 protein belongs to Mitogen-activated protein kinases family that link extracellular stimuli with intracellular responses participating in numerous of fundamental cell processes. Persistent activation of STAT3 has been associated with cell proliferation, differentiation and apoptosis in oral squamous cell carcinoma (OSCC). This study examines the effects of p38 modulation on STAT3 signaling and cellular activities in OSCC cells and investigates possible correlation of p38 expression with tumor degree of differentiation. Phospho-p38 immunostaining was performed in 60 OSCC including well, moderately and poorly differentiated tumors. Semiquantitative analysis was used, by calculating intensity, percentage and combined scores. Protein expression levels of STAT3 (total, tyrosine and serine phosphorylated), p38 and cyclin D1 were assessed in two OSCC cell lines. p38 inhibition was achieved by pharmacological agent(SB2023580). Cell proliferation and viability rates were also evaluated. Phospho-p38 immunoexpression was intense in almost all tumor specimens, nevertheless did not correlate with tumor differentiation. Inhibition of p38 with SB203580 did not appear to affect tyrosine or serine phosphorylated STAT3 as well as cyclin D1 levels in both cell lines. Moreover, p38 inhibition resulted in mild dose-dependent decreases in cell growth and viability in both cell lines. p38 is highly expressed in OSCC but does not seem to mediate the oncogenic STAT3 pathway. However, changes found in proliferation and viability may suggest that p38 functions as potent regulator of HNSCC. Understanding the complexity of p38 signaling and cross-talk between other major molecules, may guide the development of novel pharmacologic therapies for cancer treatment and prevention. © 2018, Arányi Lajos Foundation

Langerhans cell histiocytosis of the gingival mucosa with three recurrences over a 27 year period

Langerhans cell histiocytosis (LCH) is a group of rare and enigmatic disorders of the reticuloendothelial system characterised by abnormal, possibly neoplastic, proliferation of Langerhans cells. Oral lesions, in particular osteolytic lesions of the jaws, may be the primary or the sole manifestation of the disease. A 44 year old woman with a history of eosinophilic granuloma on the lower left canine region excised 25 years ago presented with an asymptomatic, ulcerated gingival lesion, extending lingual and distal to the right mandibular second premolar tooth, which was noticed approximately 6 months ago. The underlying bone was not involved. Histopathologic and immunohistochemical examination showed an LCH, consistent with eosinophilic granuloma. Radiotherapy was given, and 10 months later she developed three small painful ulcers located on the palatal gingivae around the right canine, between the second premolar and first molar, and around the right third molar, also diagnosed as eosinophilic granuloma. Eosinophilic granuloma may present in the gingival mucosa, in the absence of bone involvement, and may run a protracted course with remissions, reactivation and progression from single system to multi-system involvement. Therefore, long-term periodical follow-up and restaging is mandatory. The presence of a high proportion of plasma cells expressing lambda-light chains may cause a diagnostic dilemma with plasma cell malignancy would be interesting to be evaluated in additional cases. © 2015 The British Association of Oral Surgeons and John Wiley & Sons Ltd

The tumorigenic role of DSPP and its potential regulation of the unfolded protein response and ER stress in oral cancer cells

Dentin sialophosphoprotein (DSPP) is upregulated in various human cancers, including head and neck squamous cell carcinoma. Cancer cells are commonly found under constant endoplasmic reticulum (ER) stress and exhibit increased levels of misfolded proteins, due to gene mutations and a stressful microenvironment. The present study examined the effects of DSPP silencing on the regulation of ER stress and the unfolded protein response (UPR) in oral cancer cells. A recently established stable DSPP short hairpin (sh)RNA-silenced OSC2 oral cancer cell line was used. The mRNA expression levels of ER stress-associated proteins, including 78 kDa glucose-regulated protein (GRP78), sarcoplasmic/endoplasmic reticulum calcium ATPase 2b (SERCA2b), inositol 1,4,5-trisphosphate receptor (IP3r), protein kinase R-like endoplasmic reticulum kinase (PERK), serine/threonine-protein kinase/endoribonuclease IRE1 (IRE1), activating transcription factor 6 (ATF6) and matrix metalloproteinase 20 (MMP20), were assessed by reverse transcription-quantitative polymerase chain reaction. The expression levels of apoptosis-related [B-cell lymphoma 2 (Bcl2), Bcl2-associated X protein (Bax) and cytochrome c] and cell proliferation-related [proliferating cell nuclear antigen (PCNA)] proteins were analyzed by western blotting. Cell viability, apoptosis and migration were monitored by MTT assay, Annexin V-fluorescein isothiocyanate flow cytometry and wound-healing assay, respectively. In transiently trans-fected puromycin-free OSC2 cells, DSPP silencing markedly downregulated the mRNA expression levels of major ER stress regulators, including GRP78, SERCA2b, PERK, IRE1 and ATF6, as well as MMP20. DSPP silencing also resulted in decreased cell viability and migration, and enhanced apoptosis. Furthermore, PCNA and Bcl2 levels were decreased, whereas Bax and cytochrome c protein levels were increased in DSPP-silenced OSC2 cells. Sustained puromycin treatment partially counteracted the effects of DSPP silencing on the mRNA expression levels of ER stress-related proteins and MMP20, and on the migratory capacity of OSC2 cells. However, following puromycin treatment of DSPP-silenced cells, cell viability was further reduced and apoptosis was enhanced. In conclusion, these data provide evidence to suggest that DSPP may be involved in ER stress mechanisms in oral squamous cell carcinoma, since its downregulation in OSC2 cells led to significant alterations in the levels of major ER stress-associated proteins, and subsequent collapse of the UPR system. © 2018 Spandidos Publications. All rights reserved

Interferon γ suppresses dentin sialophosphoprotein in oral squamous cell carcinoma cells resulting in antitumor effects, via modulation of the endoplasmic reticulum response

The expression of proinflammatory cytokines in various malignant neoplasms is widely considered to represent the host immune response to tumor development. The role of interferon (IFN)γ in head and neck squamous cell carcinoma, and its association with endoplasmic reticulum (ER) stress pathways, remains a subject of ongoing investigation. Dentin sialophosphoprotein (DSPP), which is a member of the small integrin.binding N.linked glycoproteins family, has been implicated in malignant transformation and invasion of oral squamous cell carcinoma (OSCC). Recent studies have established matrix metalloproteinase (MMP)20 as the cognate MMP partner of DSPP. The present study examined the effects of IFNγ treatment on DSPP and MMP20 expression, ER stress, the unfolded protein response (UPR), and calcium (Ca) homeostasis regulatory mechanisms in OSCC cells. The OSC2 OSCC cell line was treated with IFNγ at specific time.points. At each time.point, the mRNA expression levels of DSPP and MMP20, and those of ER.stress., UPR. and Ca homeostasis.associated proteins [78.kDa glucose.regulated protein (GRP78), sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2b), inositol 1,4,5-trisphosphate receptor (IP3r), protein kinase R.like ER kinase (PERK) and inositol.requiring enzyme 1 (IRE1)], were assessed by reverse transcription.quantitative polymerase chain reaction. The protein expression levels of B.cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), proliferating cell nuclear antigen (PCNA) and cytochrome c were analyzed by western blotting. Cell viability, apoptosis and migration were evaluated by MTT, Annexin V.fluorescein isothiocyanate flow cytometry and wound.healing assays, respectively. IFNγ treatment significantly downregulated the mRNA expression levels of the major ER stress regulator GRP78 and, to a lesser extent, the UPR.associated molecule IRE1; however, IFNγ had no significant effect on PERK. With regards to ER Ca homeostasis molecules, treatment with IFNγ downregulated the mRNA expression levels of SERCA2b and upregulated those of IP3r. Furthermore, DSPP and MMP20 mRNA expression levels were significantly reduced following IFNγ treatment. Notably, treatment with IFNγ hampered OSC2 migration, reduced cell viability and PCNA protein expression, enhanced apoptosis, downregulated Bcl-2, and upregulated Bax and cytochrome c. Overall, IFNγ inhibited OSCC cell viability and migration, and increased apoptosis, possibly by regulating ER stress and UPR mechanisms. In addition, IFNγ.induced DSPP and MMP20 downregulation may correspond with alteration in ER Ca homeostasis. © Spandidos Publications 2018. All rights reserved

JNK1/2 expression and modulation of STAT3 signaling in oral cancer

Mitogen-activated protein kinases (MAPKs) are a family of protein kinases that link extracellular stimuli with intracellular responses and participate in numerous cellular processes such as growth, proliferation, differentiation, inflammation and apoptosis. Persistent activation of signal transducer and activator of transcription 3 (STAT3), which is accompanied by increases in STAT3 tyrosine phosphorylation, is associated with cell proliferation, differentiation and apoptosis in oral squamous cell carcinoma (OSCC). The role and significance of the activation of MAPKs, particularly of c-Jun N-terminal kinase (JNK), on STAT3 signaling in OSCC have not been thoroughly investigated. The present study examines the effects of JNK1/2 modulation on STAT3 signaling and cellular activities in OSCC cells. The expression levels of STAT3 [total, tyrosine phosphorylated (p-Tyr) and serine phosphorylated (p-Ser)], JNK, c-Jun and cyclin D1 were assessed in the OSCC cell lines SCC25 and SCC9. Inhibition of JNK1/2 was achieved by pharmacological agents (SP600125) and by small interfering RNA (siRNA) silencing, while JNK1/2 was induced by active MAPK kinase 7. Cell proliferation and viability rates were also evaluated. Inhibition of JNK1/2 with either SP600125 treatment or specific siRNA silencing resulted in decreased levels of p-Ser STAT3 and increased levels of p-Tyr STAT3 and cyclin D1 in both cell lines. Furthermore, JNK1/2 inhibition resulted in a dose-dependent increase in cell growth and viability in both cell lines. Opposite results were observed with JNK1/2 induction in both cell lines. The present results are supportive of a potential tumor suppressive role of JNK1/2 signaling in OSCC, which may be mediated through negative crosstalk with the oncogenic STAT3 signaling pathway. The possible therapeutic implications of JNK1/2 inhibition for patients with OSCC require to be investigated. © 2016, Spandidos Publications. All rights reserved

A preliminary immunohistochemical study of signal transducer and activator of transcription (STAT) proteins in primary oral malignant melanoma

Objective: Primary oral malignant melanoma (POMM) is a rare type of malignancy with a very poor prognosis, the molecular pathogenesis of which remains elusive. The aim of this study was to assess the expression status of signal transducer and activator of transcription (STAT) proteins in POMM. Study Design: Six POMMs were included in the study. Total protein levels of STAT1, STAT3, and STAT5a, as well as the tyrosine phosphorylated (activated) form of STAT3 (pSTAT3), were assessed immunohistochemically. Results: Immunohistochemical evaluation of total STAT3 revealed diffuse and strong cytoplasmic and nuclear expression in the majority of tumor cells of all cases, whereas activated pSTAT3 had mostly mild nuclear expression in 5%-40% of malignant melanocytes in all cases. Evaluation of STAT1 and STAT5a identified mainly mild cytoplasmic expression in the absence of nuclear localization. Conclusion: The identification of aberrant STAT3 expression and activation in oral malignant melanocytes supports a possible role of this molecule in POMM. In contrast, STAT5a has only limited cytoplasmic expression, mitigating against its involvement in POMM. Also, STAT1's low levels may have implications for POMM sensitivity to interferon-based therapeutic strategies, considering the role of this molecule in cutaneous melanoma immunotherapy. © 201

ERK1/2, JNK and STAT3 activation and correlation with tumor differentiation in oral SCC

Signal transducer and activator of transcription 3 (STAT3) and mitogen activated protein kinases (MAPKs), including ERK and JNK, have been implicated in oral squamous cell carcinoma (OSCC) development and progression. Our purpose was to evaluate the levels of activated STAT3, ERK1/2 and JNK by immunohistochemistry in OSCC and to investigate possible correlations of these molecules with each other as well as with the degree of tumor differentiation. Immunohistochemical assessment of the phosphorylated levels of STAT3(tyrosine/ serine), ERK1/2 and JNK was performed in 60 OSCC, including well, moderately and poorly differentiated tumors. Semiquantitative scoring system was used, by calculating intensity of immunostaining, percentage of positive cells and combined scores. Statistics included Fisher’s test, Student’s T-Test and Kruskal-Wallis analysis, Spearman’s correlation coefficient and multivariate logistic regression analyses. Immunohistochemical levels of both pSTAT3(tyr) and pERK1/2 showed statistically significant differences between well and poorly differentiated tumors with the latter receiving higher mean percentage, intensity and total scores. On the other hand, pJNK showed statistically significantly higher intensity levels in moderately compared to poorly differentiated tumors. pSTAT3(ser) immunoexpression did not appear to correlate with tumor differentiation. Between different molecules, more pronounced, pERK1/2 levels exhibited statistically significant positive correlation with pSTAT3(ser), pSTAT3(tyr) and pJNK expression. ERK1/2 and STAT3 activation (as assessed by tyrosine but not serine phosphorylation) could contribute to a less differentiated phenotype in OSCC, while JNK activation may have an opposite, although possibly less pronounced, effect. Positive correlations between MAPK and STAT3 levels may indicate a direct crosstalk and/or regulation by common upstream pathways. © 2017, Histology and Histopathology. All rights reserved

ERK1/2, JNK and STAT3 activation and correlation with tumor differentiation in oral SCC

Signal transducer and activator of transcription 3 (STAT3) and mitogen activated protein kinases (MAPKs), including ERK and JNK, have been implicated in oral squamous cell carcinoma (OSCC) development and progression. Our purpose was to evaluate the levels of activated STAT3, ERK1/2 and JNK by immunohistochemistry in OSCC and to investigate possible correlations of these molecules with each other as well as with the degree of tumor differentiation. Immunohistochemical assessment of the phosphorylated levels of STAT3(tyrosine/ serine), ERK1/2 and JNK was performed in 60 OSCC, including well, moderately and poorly differentiated tumors. Semiquantitative scoring system was used, by calculating intensity of immunostaining, percentage of positive cells and combined scores. Statistics included Fisher’s test, Student’s T-Test and Kruskal-Wallis analysis, Spearman’s correlation coefficient and multivariate logistic regression analyses. Immunohistochemical levels of both pSTAT3(tyr) and pERK1/2 showed statistically significant differences between well and poorly differentiated tumors with the latter receiving higher mean percentage, intensity and total scores. On the other hand, pJNK showed statistically significantly higher intensity levels in moderately compared to poorly differentiated tumors. pSTAT3(ser) immunoexpression did not appear to correlate with tumor differentiation. Between different molecules, more pronounced, pERK1/2 levels exhibited statistically significant positive correlation with pSTAT3(ser), pSTAT3(tyr) and pJNK expression. ERK1/2 and STAT3 activation (as assessed by tyrosine but not serine phosphorylation) could contribute to a less differentiated phenotype in OSCC, while JNK activation may have an opposite, although possibly less pronounced, effect. Positive correlations between MAPK and STAT3 levels may indicate a direct crosstalk and/or regulation by common upstream pathways

Alterations in the expression of DNA damage response-related molecules in potentially preneoplastic oral epithelial lesions

Objectives: The aim of this study was to evaluate the expression levels of DNA damage response (DDR) markers in potentially preneoplastic oral epithelial lesions (PPOELs). Study Design: Immunohistochemical expression of DDR markers (γΗ2 ΑΧ pChk2, 53 BP1, p53, and phosphorylated at Ser 15 p53) was assessed in 41 oral leukoplakias, ranging from hyperplasia (H) to dysplasia (D) and in comparison with oral squamous cell carcinoma (OSCC) and normal mucosa (NM). Statistical and receiver operating characteristic curve analysis were performed. Results: γH2 AX immunoexpression demonstrated a gradual increase and upper layer extension from NM to H to higher D degrees to OSCC. pChk2 expression was minimal in NM, relatively low in PPOELs, with an increasing tendency from H to D, and higher in OSCC. 53 BP1 demonstrated higher levels in OSCC than in NM, whereas its expression in PPOELs was heterogeneous, gradually increasing according to D. p53 demonstrated progressively higher levels and upper layer extension from H to D to OSCC. Phosphorylated p53 was absent in NM and relatively low in PPOELs and OSCC. Conclusions: DDR markers’ expression is variable in PPOELs, showing a tendency to increase along with dysplasia. Activated DDR mechanisms may play an important protective role at early stages of oral carcinogenesis, but probably suffer progressive deregulation, eventually failing to suppress malignant transformation. © 201