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Objectives: The improved survival of patients with oral cavity cancer (OCC) has generated interest in factors affecting survivorship, particularly among second primary cancer (SPC) patients. This study aimed to assess the incidence, patterns, and risk factors for SPC after OCC treatment in the Korean population., Materials and Methods: Data from 15,261 patients with OCC (ICD-O: C01-C06) identified between 1993 and 2014 were extracted from the Korean Central Cancer Registry. The standardized incidence ratio (SIR) for SPC after index OCC was calculated, and Poisson regression analysis was performed to evaluate the risk factors for SPC among survivors., Results: The overall SIR for SPC among OCC survivors was 1.47 (95% confidence interval [CI] 1.39-1.56). SIR differed by sex (male: 1.51 vs. female: 1.37), age at diagnosis (<45 years: 2.47 vs. 45-64 years: 1.68 vs. ≥ 65 years: 1.10), index OCC subsite (floor of mouth: 1.95 vs. gum: 1.30), follow-up duration (6-23 months: 1.64 vs. 24-59 months: 1.51 vs. 60-119 months: 1.48 vs. ≥ 120 months: 1.24), histological OCC type (salivary gland malignancy: 1.77 vs. squamous cell carcinoma: 1.44 vs. others: 1.47), and radiation history (any: 1.94 vs. no radiation: 1.37). The risk factors for SPC development among OCC survivors included younger age at diagnosis and history of radiation therapy., Conclusion: OCC survivors have significantly increased risks of SPCs, exhibiting distinctive site distributions and chronological patterns. These patients would benefit from an SPC surveillance protocol., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Numerous studies implicate miR-146a as pleiotropic regulator of carcinogenesis; however, its roles in carcinogenesis are not fully understood. A clue from expression analyses of miR-146a-5p in all 13 oral squamous cell carcinoma (OSCC) cell lines examined and in OSCC tissues, whole blood and whole saliva of OSCC patients in vivo revealed that miR‑146a-5p expression was highly upregulated. Particularly, we widened the view of its upregulation in saliva, implicating that high miR-146a-5p expression is not only correlated closely to the development of human oral cancer, but also to a possible candidate as a diagnostic marker of OSCC. Indeed, further examination showed that exogenous miR-146a-5p expression showed pleiotropic effects on cell proliferation and apoptosis which were partially based on the contextual responses of activation of JNK, downstream of TRAF6 that was targeted by miR-146a-5p in normal human keratinocytes and OSCC cell lines. TRAF6 suppression by a TRAF6-specific siRNA resulted in contradictory consequences on cellular processes in normal and OSCC cells. Notably, TRAF6 downregulation by both miR-146a-5p and TRAF6-specific siRNA deactivated JNK in SCC-9, but not in normal human keratinocytes. In support of the proliferation-promoting effect of miR-146a-5p, silencing of endogenous miR-146a-5p significantly reduced proliferation of SCC-9. Together, these results suggest that miR-146a-5p affects proliferation and apoptosis in a cellular context-dependent manner and selectively disarms the TRAF6-mediated branch of the TGF-β signaling in OSCC cell lines by sparing Smad4 involvement.

Objectives: Conditional relative survival (CRS) describes the survival chance of patients who have already survived for a certain period of time after diagnosis and treatment of cancer. Thus, CRS can complement the conventional 5-year relative survival, which does not consider the time patients have survived after their diagnosis. This study aimed to assess the 5-year CRS among Korean patients with oral cancer and the related risk factors., Materials and Methods: We identified 15,329 oral cavity cancer cases with a diagnosis between 1993 and 2013 in the Korea Central Cancer Registry. The CRS rates were calculated according to sex, age, subsite, histology, and stage at diagnosis., Results: The 5-year relative survival was 57.2%, and further analysis revealed that the 5-year CRS increased during the first 2years and reached a plateau at 86.5% after 5years of survival. Women had better 5-year CRS than men after 5years of survival (90.0% vs. 83.3%), and ≤45-year-old patients had better 5-year CRS than older patient groups (93.3% vs. 86.4% or 86.7%). Subsite-specific differences in 5-year CRS were observed (tongue: 91% vs. mouth floor: 73.9%). Squamous cell carcinoma had a CRS of 87.3%, compared to 85.5% for other histological types. Localized disease had a CRS of 95.7%, compared to 87.3% for regional metastasis., Conclusion: Patients with oral cavity cancer exhibited increasing CRS rates, which varied according to sex, age, subsite, histology, and stage at diagnosis. Thus, CRS analysis provides a more detailed perspective regarding survival during the years after the initial diagnosis or treatment., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Pheophorbide a (Pa) is a chlorine-based photosensitizer derived from an ethnopharmacological herb, and our group recently synthesized Pa by the removal of a magnesium ion and a phytyl group from chlorophyll-a. In this study, the effect of photodynamic therapy (PDT) with synthesized Pa was examined in a human oral squamous cell carcinoma (OSCC) cells., Methods: Cells were treated with PDT with Pa, and reactive oxygen species (ROS) and mitochondrial membrane potential [ΔΨ (m)] were examined. Apoptosis was measured using annexin V staining and immunoblot. Autophagy was characterized by the increase in LC3B-II and the formation of autophagosome and acidic vesicular organelles (AVOs)., Results: Pa-PDT inhibited the proliferation of OSCC cells in a dose-dependent manner. Pa-PDT increased the number of apoptotic cells by inactivating ERK pathway. Pa-PDT also induced autophagy in OSCC cells evidenced by the increased levels of LC3 type II expression and the accumulation of AVOs. The inhibition of autophagy enhanced Pa-PDT-mediated cytotoxicity through an increase in necrosis., Conclusions: These results suggest that synthesized Pa-PDT exerts anti-tumor effects by inducing apoptosis and autophagy and provide novel evidence that Pa-PDT induces autophagy, and autophagy inhibition enhances Pa-PDT-mediated necrosis in OSCC cells., (© 2012 John Wiley & Sons A/S.)

Background: Toll-like receptor (TLR) agonists have anticancer effect by inducing apoptosis or activating immune cells. In this study, we investigated whether imiquimod, TLR7 agonist, inhibits the proliferation of oral cancer cells., Methods: Toll-like receptor 7 expression and IL-6/8 production by imiquimod were examined using RT-PCR and Enzyme-linked immunosorbent assay, respectively. Cell viability was examined by MTT assay. To examine apoptotic cell death, Annexin V/PI staining for flow cytometry and Western blot analysis were performed. Necrotic cell death was determined by leakage of lactate dehydrogenase (LDH), HMGB1, and PI staining in imiquimod-treated oral squamous cell carcinoma (OSCC) cells., Results: Toll-like receptor 7 mRNA was expressed in OSCC cells. Imiquimod induced IL-6 and IL-8 production in OSCC cells, suggesting the functional expression of TLR7. Imiquimod inhibited cells proliferation in a dose-dependent manner. The ratio of annexin V-positive cells and cleaved caspase-3/7 was increased by imiquimod treatment in OSCC cells, suggesting that imiquimod-induced cell death in OSCC cells may be owing to apoptosis. In addition, LDH secretion and PI staining were detected in OSCC cells treated with imiquimod, showing that imiquimod also induced necrotic cell death in the OSCC cells., Conclusions: Imiquimod inhibited effectively the growth of OSCC cells by inducing apoptosis and necrosis., (© 2012 John Wiley & Sons A/S.)

Although >60% of oral cancer cases are not related to human papillomavirus (HPV) infection, most studies of oral carcinogenesis in human cells in vitro are carried out with human oral keratinocytes immortalized by HPV DNA. To explore whether human oral keratinocytes can spontaneously transform without HPV infection, we attempted to establish spontaneously immortalized and tumorigenic-transformed human oral keratinocytes by serial subculture to the post-mitotic stage. Here we report two spontaneously transformed human oral keratinocyte lines from adult human gingival samples. These lines were obviously immortal (>140 passages) and transformed phenotypes in vitro. One of the lines, Spi-HOK1, remained non-tumorigenic in nude mice, whereas the other line, Spt-HOK80, showed tumorigenicity. These lines showed epithelial origi-nality, but did not contain high-risk types of HPV DNAs. On karyotyping, Spi-HOK1 was aneuploid with a unique stable marker chromosome. Both cell lines revealed a mutation in the p53 gene, loss of p21WAF1/Cip1 and overexpression of p-Rb-Ser807/811. These cell lines were resistant to cisplatin-induced apoptosis by suppressing induction of apoptotic proteins. These results clearly demonstrate that spontaneous immortalization and spontaneous tumorigenic transformation of primary human oral keratinocytes can occur in vitro without HPV infection and are associated with chromosomal alterations, p53 mutation and impaired apoptosis. To our knowledge, this is the first report demonstrating that the Spi-HOK1 and Spt-HOK80 lines are novel cell lines that are spontaneously transformed from primary human oral keratinocytes.

Background: Although N(1)-guanyl-1,7,-diamineoheptane (GC7), an inhibitor of deoxyhypusine synthase, has been shown to inhibit cell growth, the mechanism of its action is not completely understood. In this study, we investigated the mechanisms of the effects of GC7 on cell growth, differentiation and apoptosis in relation to adenosine monophosphate-activated protein kinase (AMPK) activation, as AMPK is known to be a possible target for cancer treatment., Methods: The effects of GC7 on the growth of immortalized human oral keratinocytes (IHOK) and primary oral cancer cells (HN4), was investigated using MTT assay, Western blotting, cell cycle analysis, DNA fragmentation and expression of apoptotic pathway proteins., Results: N(1)-guanyl-1,7,-diamineoheptane inhibited cell proliferation in a time- and dose-dependent manner in IHOK and HN4 cells. GC7 treatment decreased the expression of differentiation markers, such as involucrin, CK13 and CK19. The major mechanism of growth inhibition by GC7 treatment was induction of apoptosis, which is supported by sub-G(1) phase arrest, annexin V-FITC staining and DNA fragmentation analysis. GC7 treatment increased the cytosolic level of cytochrome c and resulted in caspase-3 activation. GC7 treatment also resulted in a strong activation of AMPK. Furthermore, specific AMPK activator blocked the GC7-induced growth inhibition effect, as well as apoptosis., Conclusion: These results demonstrate that GC7 blocks immortalized and malignant keratinocyte cell proliferation and differentiation by inducing apoptosis through the mitochondrial and AMPK pathways. On the basis of these observations, we propose that a strategy combining GC7 and AMPK inhibition could be developed into a novel chemotherapeutic modality in oral cancer.

Background: Although hydrogen peroxide may play an important role in the development of cancer, it can be an efficient inducer of apoptosis in cancer cells; the exact mechanism by which this action occurs is not completely understood in oral cancer cells., Method: In this study, the mechanisms by which H(2)O(2) inhibited growth and induced apoptosis were differentially investigated using HPV-immortalized human oral keratinocytes (IHOK) and oral cancer cells (HN4)., Results: H(2)O(2) treatment sensitively and dose-dependently induced growth inhibition and typical apoptosis in IHOK and HN4 cells, as demonstrated by a decreased level of cell viability, an increased population of cells in the sub-G(0)/G(1) phase, ladder formation of the genomic DNA, chromatin condensation and accumulation of Annexin V(+)/PI(+) cells. Furthermore, the expression of Bax, p53 and p21(WAF1/CIP1) increased, whereas the expression of Bcl-2 decreased in immortalized and malignant keratinocytes that were treated with H(2)O(2). In addition, cytochrome-c from the mitochondria was observed in H(2)O(2)-treated IHOK and oral cancer cells, and this was accompanied by the activation of caspase-3 and -9. Additionally, H(2)O(2) treatment induced upregulation of CHOP, GRP78 and several representative endoplasmic reticulum (ER) stress-responsive proteins, including heme oxygenase-1., Conclusion: Overall, these results suggest that H(2)O(2) triggers apoptosis via the mitochondrial and ER stress pathway in IHOK and HN4 cells, and that increasing the cellular levels of H(2)O(2) sufficiently may lead to selective killing of oral cancer cells and therefore be therapeutically useful.

Macrophage inflammatory protein-3alpha (MIP-3alpha or CCL20) is an intriguing molecule in cancer immunotherapy, but MIP-3alpha expression and signalling are not well understood in oral cancer cells. We investigated CCL20 expression and signal transduction by treating immortalized human oral keratinocyte (IHOK) and oral cancer (HN4) cells with deferoxamine (DFO) and examined the mRNA expression of CCL20 using RT-PCR and ELISA. IHOK and HN4 cells treated with DFO showed increased mRNA and protein expression of CCL20, and the upregulation of DFO-induced CCL20 expression was higher in IHOK cells than in HN4 cells. Selective inhibitors of p38 and ERK1/2 abolished DFO-induced CCL20 expression in both IHOK and HN12 cells, and p38 and ERK1/2 inhibitors prevented DFO-induced degradation of I-kappaB and NF-kappaB activation. Activation of c-fos and c-jun also occurred following DFO treatment in IHOK and HN4 cells. Collectively, these results suggest that DFO-induced MIP-3alpha, which is involved in the MAP kinase, c-fos, c-jun, and NF-kappaB pathways, may be an important mediator of the antitumour immune response in oral keratinocytes and warrants consideration as a target molecule for oral cancer treatment.