Ophiopogonin D (OPD) is a steroidal glycoside derived from Ophiopogon japonicus , a traditional Chinese medicine with diverse biological activities, including antithrombosis, anti-inflammation, and antitussive effects. To investigate the cellular effects and mechanisms of OPD on oral squamous cell carcinoma, cell viability was explored, and the effects of OPD on cell cycle regulators, apoptotic marker proteins, and key proteins involved in metastasis and signaling pathways were examined by MTT assay and Western blotting in YD38 cells. OPD strongly inhibited cell proliferation and induced caspase-dependent apoptosis of YD38 cells by suppressing the cell cycle and activating caspase-3 and poly ADP ribose polymerase. Additionally, OPD suppressed the expression of vital proteins regulating metastasis and proliferation within the integrin/matrix metalloproteinases/FAK and AKT/PI3K/mTor pathways. Thus, OPD can be a potential treatment candidate for gingival cancer.

Orthokeratinized odontogenic cysts are developmental cysts that occur in the jaw that account for approximately 7%–17% of all cysts in the jaws. Studies have shown that malignant transformation of odontogenic cysts most often occurs in inflammatory cysts, such as periapical cysts, but malignant transformation of orthokeratinized odontogenic cysts has also been reported. In this report, we present an uncommon case of squamous cell carcinoma arising from an orthokeratinized odontogenic cyst.

Despite advancements in therapeutic approaches, radiotherapy and cisplatin-based chemotherapy remain primary noninvasive treatments for patients with oral squamous cell carcinoma (OSCC). Moreover, the 5-year survival rate for patients with OSCC has remained almost unchanged for several decades, and many side effects of chemotherapy still exist. In this study, three-dimensional (3D) models of OSCC were established using fibroblasts, and the efficacy of various biological inhibitors was evaluated. A culture of epithelial cells with two types of fibroblasts (hTERT-hNOFs and cancer-associated fibroblasts) within a type I collagen matrix resulted in the formation of a continuous layer of tightly packed cells compared to models without fibroblasts. Furthermore, the effects of biological chemicals, including Y27632, latrunculin A, and verteporfin, on these models were investigated. The stratified formation of the epithelial layer and invasion in OSCC 3D-culture models were effectively inhibited by verteporfin, whereas invasion was weakly inhibited by Y27632 and latrunculin. Collectively, the developed OSCC 3D-culture models established with fibroblasts demonstrated the potential for drug screening, with verteporfin showing promising efficacy.

Oral bacterial infections substantially affect the development of various periodontal diseases and oral cancers. However, the molecular mechanisms underlying the association between Fusobacterium nucleatum (F. nucleatum ), a major periodontitis (PT)-associated pathogen, and these diseases require extensive research. Previously, our RNAsequencing analysis identified a few hundred differentially expressed genes in patients with PT and peri-implantitis (PI) than in healthy controls. Thus, in the present study using oral squamous cell carcinoma (OSCC) cells, we aimed to evaluate the effect of F. nucleatum infection on genes that are differentially regulated in patients with PT and PI. Human oral squamous cell carcinoma cell lines OSC-2O, HSC-4, and HN22 were used. These cells were infected with F. nucleatum at a multiplicity of infection of 100 for 3 hours at 37℃ in 5% CO2. Gene expression was then measured using reverse-transcription polymerase chain reaction. Among 18 genes tested, the expression of CSF3, an inflammation-related cytokine, was increased by F. nucleatum infection. Additionally, F. nucleatum infection increased the phosphorylation of AKT, p38 MAPK, and JNK in OSC-20 cells. Treatment with p38 MAPK (SB202190) and JNK (SP600125) inhibitors reduced the enhanced CSF3 expression induced by F. nucleatum infection. Overall, this study demonstrated that F. nucleatum promotes CSF3 expression in OSCC cells through p38 MAPK and JNK signaling pathways, suggesting that p38 MAPK and JNK inhibitors may help treat F. nucleatum-related periodontal diseases by suppressing CSF3 expression.

Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, and it has been steadily increasing in worldwide. Pituitary tumor transforming gene 1 (PTTG1) has been known as oncogene in a verity of cancers. Nevertheless, the expression and role of PTTG1 in OSCC progression remains largely unexplored. In this study, clinical datasets were analyzed to assess the genetic impact of PTTG1 on OSCC progression and to identify its functional roles in OSCC cell lines. We analyzed the expression of PTTG1 in head and neck squamous cell carcinoma (HNSC) and OSCC using databases form the Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). To investigate the effect of PTTG1 on proliferation and migration abilities in OSCC cell lines, following the knockdown of PTTG1 in HSC-2 and SCC-9 cell lines, we analyzed the proliferation and metastatic abilities of OSCC cells using EdU and Boyden chamber assays. Our database analysis revealed that PTTG1 was significantly overexpressed in tumor tissues compared to normal tissues. Moreover, its expression correlated with clinical parameters of OSCC. In vitro experiments demonstrated that depletion of PTTG1 suppressed the ability of cell proliferation and migration in both HSC-2 and SCC-9 cell lines. In conclusion, our study suggests that PTTG1 may act as an oncogene in OSCC. These findings provide new insights into the mechanisms and clinical implications of PTTG1 expression in OSCC patients.

Oral squamous cell carcinoma (OSCC), which accounts for approximately 90% of oral cancers, has a high rate of local recurrence and a poor prognosis despite improvements in treatment. Exosomes released from OSCC cells promote cell proliferation and metastasis. Although it is clear that the biogenesis of exosomes is mediated by the endosomal sorting complex required for transport (ESCRT) machinery, the gene expression pattern of ESCRT, depending on the cell type, remains elusive. The exosomal release from the human OSCC cell lines, HSC-3 and HSC-4, and their corresponding gefitinib-resistant sub-cell lines, HSC-3/GR and HSC-4/GR, was assessed by western blot and flow cytometry. The levels of ESCRT machinery proteins, including Hrs, Tsg101, and Alix, and whole-cell ubiquitination were evaluated by western blot. We observed that the basal level of exosomal release was higher in HSC-3/GR and HSC-4/GR cells than in HSC-3 and HSC-4 cells, respectively. Long-term gefitinib exposure of each cell line and its corresponding gefitinib-resistant sub-cell line differentially induced the expression of the ESCRT machinery. Furthermore, whole-cell ubiquitination and autophagic flux were shown to be increased in gefitinib-treated HSC-3 and HSC-4 cells. Our data indicate that the expression patterns of the ESCRT machinery genes are differentially regulated by the characteristics of cells, such as intracellular energy metabolism. Therefore, the expression patterns of the ESCRT machinery should be considered as a key factor to improve the treatment strategy for OSCC.

Oral squamous cell carcinoma (OSCC) is the most common type of head and neck cancer and is associated with high recurrence, poor treatment, and low survival rates. Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that regulates the response to hypoxia, a major factor in the tumor microenvironment that affects tumor development and progression in various cancer types. However, microRNA (miRNA) sequence analysis revealed that only a few miRNAs targeting HIF-1α had been discovered. In the present study, we investigated HIF-1α expression in OSCC and the effect of HIF-1α-targeting miRNAs on the progression and metastatic potential of OSCC. We analyzed public databases to explore which miRNAs target HIF-1α expression. In addition, the expression of proteins involved in the cell cycle, proliferation, and apoptosis in HSC-2 cells was analyzed after miRNA-126 mimic treatment. Furthermore, to investigate the effect of miRNA-126 on the proliferation and invasion ability of OSCC cells, 5-ethynyl-2′-deoxyuridine and Transwell assays were performed. The activities of MMP-2 and MMP-9 were evaluated via gelatin zymography. Our results showed that miRNA-126, which targets HIF-1α, enhances OSCC cell proliferation by regulating the cell cycle and reinforces the cell mobility of OSCC via HIF-1α expression. These findings suggest that miRNA-126 may be a novel marker for OSCC treatment and the development of new tools for patients with OSCC.

Despite evidence that bacteria-sensing Toll-like receptors (TLRs) are activated in salivary gland tissues of Sjogren syndrome (SS) patients, the role of oral bacteria in SS etiopathogenesis is unclear. We previously reported that two SS-associated oral bacteria, Prevotella melaninogenica (Pm) and Rothia mucilagenosa (Rm), oppositely regulate the expression of major histocompatibility complex class I (MHC I) in human salivary gland (HSG) cells. Here, we elucidated the mechanisms underlying the differential regulation of MHC I expression by these bacteria. The ability of Pm and Rm to activate TLR2, TLR4, and TLR9 was examined using TLR reporter cells. HSG cells were stimulated by the TLR ligands, Pm, and Rm. The levels of MHC I expression, bacterial invasion, and viability of HSG cells were examined by flow cytometry. The hypoxic status of HSG cells was examined using Hypoxia Green. HSG cells upregulated MHC I expression in response to TLR2, TLR4, and TLR9 activation. Both Pm and Rm activated TLR2 and TLR9 but not TLR4. Rm-induced downregulation of MHC I strongly correlated with bacterial invasion and cell death. Rm-induced cell death was not rescued by inhibitors of the diverse cell death pathways but was associated with hypoxia. In conclusion, Pm upregulated MHC I likely through TLR2 and TLR9 activation, while Rm-induced hypoxia-associated cell death and the downregulation of MHC I, despite its ability to activate TLR2 and TLR9. These findings may provide new insight into how oral dysbiosis can contribute to salivary gland tissue damage in SS.

Autophagy is an evolutionarily well-conserved cellular homeostasis program that responds to various cellular stresses and degrades unnecessary or harmful intracellular materials in lysosomes. Accumulating evidence has shown that autophagy dysfunction often results in various human pathophysiological conditions, including metabolic disorders, cancers, and neurodegenerative diseases. The discovery of an autophagy machinery protein network has revealed underlying molecular mechanisms of autophagy, and advances in the understanding of its regulatory mechanism have provided novel therapeutic targets for treating human diseases. Recently, reports have emerged on the involvement of autophagy in oral squamous cell carcinoma (OSCC). Although the role of autophagy in cancer therapy is controversial, the beneficial use of the induction of autophagic cell death in OSCC has drawn significant attention. In this review, the types of autophagy, mechanism of autophagosome biogenesis, and modulating molecules and therapeutic candidates affecting the induction of autophagic cell death in OSCC are briefly described.

Worldwide, oral cancer accounts for 2%–4% of all cancer cases. It is estimated that more of 90% of all oral neoplasms are oral squamous cell carcinoma (OSCC). The aims of this study were to evaluate follow-up outcomes in patients with OSCC invading the mandibular body bone who underwent primary radical resection and reconstructive surgery by fibular free flap or CAD-CAM T-mesh with pathological study on two cases. In this article, two cases of mandibular reconstruction in patients with OSCC invading the mandibular body bone are reported. A 68-year-old male patient visited the authors’ clinic with pain on the left mandibular region. After wide excision and segmental mandibulectomy on the mandibular OSCC, a enterocutaneous fibular free flap from right leg was used to cover the intraoral mucosal defect. The other 51-year-old female patient visited the authors’ clinic with pain on the right mandibular region. After wide excision and segmental mandibulectomy on the mandibular OSCC, reconstruction was done with a reconstruction plate and a fibula free flap from right leg. Unfortunately, fibular free flap was lost due to infection of the flap at post-operative 1month, secondary reconstruction using a custom-made type T-mesh and iliac PCBM was done to repair on the mandibular defect after four years postoperatively. The customized CAD-CAM T-mesh was made prior to the operation according to mirror image of remained jaw. Patients with OSCC invading the mandibular body bone are required an accurate segmental mandibulectomy immediate reconstructive surgery with various methods and followed by adjuvant radiation with or without chemotherapy in order to improve the quality of life through the restoration of the oral function and esthetics after surgery. Postoperative CCRT was determined according to the final pathologic findings such as lymph node metastasis and main lesion free margin safety, and this has an essential relationship in the prognosis of postoperative recurrence. We reviewed reliable treatment options on two patients of OSCC in mandible with pathologic findings.Worldwide, oral cancer accounts for 2%–4% of all cancer cases. It is estimated that more of 90% of all oral neoplasms are oral squamous cell carcinoma (OSCC). The aims of this study were to evaluate follow-up outcomes in patients with OSCC invading the mandibular body bone who underwent primary radical resection and reconstructive surgery by fibular free flap or CAD-CAM T-mesh with pathological study on two cases. In this article, two cases of mandibular reconstruction in patients with OSCC invading the mandibular body bone are reported. A 68-year-old male patient visited the authors’ clinic with pain on the left mandibular region. After wide excision and segmental mandibulectomy on the mandibular OSCC, a enterocutaneous fibular free flap from right leg was used to cover the intraoral mucosal defect. The other 51-year-old female patient visited the authors’ clinic with pain on the right mandibular region. After wide excision and segmental mandibulectomy on the mandibular OSCC, reconstruction was done with a reconstruction plate and a fibula free flap from right leg. Unfortunately, fibular free flap was lost due to infection of the flap at post-operative 1month, secondary reconstruction using a custom-made type T-mesh and iliac PCBM was done to repair on the mandibular defect after four years postoperatively. The customized CAD-CAM T-mesh was made prior to the operation according to mirror image of remained jaw. Patients with OSCC invading the mandibular body bone are required an accurate segmental mandibulectomy immediate reconstructive surgery with various methods and followed by adjuvant radiation with or without chemotherapy in order to improve the quality of life through the restoration of the oral function and esthetics after surgery. Postoperative CCRT was determined according to the final pathologic findings such as lymph node metastasis and main lesion free margin safety, and this has an essential relationship in the prognosis of postoperative recurrence. We reviewed reliable treatment options on two patients of OSCC in mandible with pathologic findings.

Resveratrol has been reported to exert anticancer activity via modulation of multiple pathways and genes. In this study, we examined the effect of resveratrol on YD-10B human oral squamous cell carcinoma cells and its molecular mechanisms of action. We found that resveratrol inhibited the proliferation of YD-10B cells in a dose- and timedependent manner. The suppressive effect of resveratrol was accompanied by a reduction in Bmi-1 gene expression. We observed that silencing the Bmi-1 gene by small interfering RNA effectively downregulated the levels of GLUT1 mRNA and protein, which were also repressed by resveratrol. Bmi-1 silencing increased the number of YD-10B cells in S-phase arrest by approximately 2.3-fold compared with the control. In conclusion, the results of the present study demonstrate, for the first time, that resveratrol suppresses Bmi-1-mediated GLUT1 expression in human oral squamous cell carcinoma cells and suggest that the specific molecular targeting of Bmi-1 and/or GLUT1 expression can be combined with a chemotherapeutic strategy to improve the response of oral cancer cells to resveratrol.

Perineural invasion (PNI) is the underestimated metastatic pathway and has been widely recognized as a negative prognostic factor in many human cancers. L1CAM is one of members of the immunoglobulin-like cell adhesion molecule (CAM) family, which play a role in neural development. Moreover, a new role of L1CAM outside the nervous system has been revealed. Overexpression of L1CAM was involved in the tumor progression and LN metastasis in various malignancies. In the present study, presence of PNI and L1CAM expression were examined to define their prognostic values in OSCC. In addition, association of L1CAM expression with presence of PNI was assessed to define the value as a candidate molecule supporting the diagnosis of PNI. We found that presence of PNI significantly correlated with LN metastasis and advanced clinical stage. L1CAM expression also significantly correlated with differentiation, lymph node metastasis, advanced clinical stage, as well as presence of PNI. Our results suggest that L1CAM seems to play a role in tumor progression, possibly through the PNI-related mechanism and could be a molecular marker for supporting the presence of PNI and predicting clinical outcome in OSCC.

Oral squamous cell carcinoma (OSCC) is the most common oral malignancy and an increasing global public health problem. OSCC frequently invades the jaw bone. OSCC-induced bone invasion has a significant impact on tumor stage, treatment selection, patient outcome, and quality of life. A number of studies have shown that osteoclastmediated bone resorption is a major step in the progression of bone invasion by OSCC; however, the molecular mechanisms involved in OSCC bone invasion are not yet clear. In this review, we present the clinical types of OSCC bone invasion and summarize the role of key molecules, including proteases, cytokines, and growth factors, in the sequential process of bone invasion. A better understanding of bone invasion will facilitate the discovery of molecular targets for early detection and treatment of OSCC bone invasion.

It is well known that lymph node metastasis is a major prognostic factor in patients with oral squamous cell carcinoma (OSCC). 30-40% of patients with OSCC have already undergone regional metastasis at diagnosis. The survival rate of patients with metastasis is reduced by more than 50%. Therefore, prevention and early detection of metastasis are very important to increase the survival rate of patients. Many investigators have studied the molecular mechanism of metastasis and tried to develop the molecules to inhibit any step of metastatic cascade. Among those molecules, an interest in the metastasis suppressor gene has been increasing. Expression of metastasis suppressor KiSS-1 has shown to be significantly related to poor clinical outcome and worse survival rate of patient in various malignancies of different organs. In addition, our previous study in OSCC also revealed that downregulation of KiSS-1 expression correlated with the presence of cervical lymph node metastasis, one part of tumor progression. Therefore, further investigation was needed to identify the molecular function of KiSS-1 using OSCC cell line and to evaluate the possibility of KiSS-1 as a new therapeutic target.

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin's lymphoma, and usually showed painless neck swelling, fever, sweat, and weight loss. Although about 5% of all lymphomas appeared in the oral area, the primary maxillofacial lymphomas were rare and sometimes clinically tended to be misdiagnosed such as chronic periodontitis, osteomyelitits, etc. This study demonstrated three cases of primary DLBCL mimicking localized osteomyelitis at mandible or maxilla. A series of histological and immunohistochemical examination using different biomarkers of lymphoreticular cells were performed to characterize the neoplastic cells of DLBCL. The first case occurred in a 45 years old male exhibiting mandibular osteomyelitis and neck swelling. The second case simply showed a gingival swelling at left upper premolar area in a 55 years old male. And the third case is from an 84 years old female who felt numbness at left lower lip and had severe periodontitis involving regional alveolar bone resorption. All of three cases had experienced no systemic manifestation of lymphoreticular malignancy before the diagnosis of oral lymphoma. Immunostainings of CD3, CD20, TNFα, BCL-2, Ki-67, PCNA, and c-Myc were strongly positive in these tumor cells, while those of p53 and CD31 were slightly positive, and CD56 immunoreaction was negative. These three cases were diagnosed as DLBCL and referred to the hemato-oncology unit for treatment. Therefore, every chronic granulomatous periodontal lesion hardly cured by simple medical treatment should be carefully explored through pathological examination, and it was presumed that DLBCL is closely related to the chronic inflammatory periodontal lesions recruiting mucosa-associated lymphoid cells in older patients. It was also suggested that DLBCL be differentially diagnosed from T-cell lymphoma, Burkitt’s lymphoma, and Hodgkin’s disease, etc. with immunohistochemical determination of tumor cell subtypes as soon as possible in order to be treated with appropriate therapy.

Recently chronic inflammation is focused on the association with cancer progression and acquisition of aggressive biologic behaviors, such as invasion, metastasis, and resistance to chemotherapeutic reagents. Due to the close vicinity within oral cavity, oral cancer may be intimately associated with chronic periodontitis. The present study was done to observe the effect of chronic periodontitis on oral cancer cells by utilizing P. gingivalis infection, a major pathogen in chronic periodontitis. We analyzed and compared the mRNA expression levels of epithelial-mesenchymal transition (EMT) markers in non-infected and P. gingivalis-infected oral cancer cells. Eighty-six genes, which are well known as EMT markers, were analyzed using commercially available EMT microarray plates, performed in triplicate. Among the 86 genes, the expression of 26 was increased (≥ 2 fold) by P. gingivalis, whereas that of 7 genes was decreased (≥ 2 fold). Our study suggests that P. gingivalis infection evokes significant changes in EMT-related genes. Further observations on molecular mechanisms underlying these changes may help to clarify the role of chronic periodontitis on cancer progression and to develop more efficient preventive and therapeutic modalities for oral cancer. (182 words)

Autophagy is recently receiving the spotlight as the development strategy for promising anticancer drugs. In particular, the majority of anticancer drugs originating from natural products are known to induce autophagy. Saururus chinensis has been used for treating various inflammatory diseases. Recent research has revealed that the extract of Saururus chinensis possess cytotoxicity for various types of human cancer cells. However, the exact action mechanism of Saururus chinensis extract for oral squamous cell carcinoma (OSCC) has not been studied yet. Therefore, the authors of this research aim to study the effect of methanol extract of S. chinensis (MESC) on OSCC cells. To observe the cell proliferation inhibitory effect of MESC on HSC3 cells, the authors conducted the trypan blue exclusion assay. Also, the action mechanism of MESC was studied by conducting the cell cycle analysis, acidic vesicular organelle (AVO) staining and flow cytometry analysis, monodansylcadaverine (MDC) staining, propidium iodide staining, and Western blotting on MESC-treated HSC3 cells. When HSC3 cells were treated in MESC, the cell proliferation was suppressed in time-dependent and dose-dependent manners. Also, the number of sub-G1 arrested cells increased in a dose-dependent manner. MDC punctate and AVO puncta significantly increased respectively. Western blot analysis demonstrated the expression of autophagy-related proteins increased, but apoptotic proteins were not observed. Also, the pAkt protein was reduced, while the p-p38 protein and pERK protein increased. According to our results, MESC induced autophagy and accompanied changes in the cell cycle in HSC3 cells. Also, the alteration in Akt, ERK, and p38 pathways were confirmed. This result suggested the possibility of MESC as the new promising adjuvant for treating OSCC patients.

Oral squamous cell carcinoma (OSCC) is the most common type of oral malignancy. Numerous therapies have been proposed for its cure. Research is continually being conducted to develop new forms of treatment as current therapies are associated with numerous side-effects. Luteolin, a common dietary flavonoid, has been demonstrated to possess strong anti-cancer activity against various human cancer cell lines. Nevertheless, research into luteolin-based anticancer activity against oral cancer remains scarce. Thus, the objective of this study was to assess the effect of luteolin as an anti-cancer agent. After treatment with luteolin, Ca9-22 and CAL-27 oral cancer cells showed condensed nuclei and enhanced apoptotic rate with evidence of mitochondria-mediated apoptosis. Epithelial-mesenchymal transition (EMT) is closely related to tumor migration and invasion. Luteolin suppressed cancer cell invasion and migration in the current study. Elevated expression of E-cadherin, an adherens junction protein, was evident in both cell lines after luteolin treatment. Luteolin also significantly inhibited transcription factors (i.e., N-cadherin, Slug, Snail, Twist, and ZEB-1) that regulated expression of tumor suppressors such as E-cadherin based on Western blot analysis and quantitative PCR. Thus, luteolin could induce mitochondrial apoptosis and inhibit cancer cell invasion and migration by suppressing EMT-induced transcription factors.

The role of CXCR7, a seven-transmembrane G-protein coupled chemokine receptor, which binds with high affinity to chemokine CXCL11 and CXCL12 in oral cancer cells and the effect of transient CXCR7-downregulation on proliferation and migration of oral squamous cell carcinoma (OSCC) cells have not been reported. The aim of the present study was to evaluate the effects of CXCR7 on an OSCC cell line. In this study, we down-regulated CXCR7 in the KOSCC25B OSCC cell line by siRNA. In vitro cell proliferation and migration assays were used to investigate the effect of CXCR7- downregulation on cell proliferation and migration in si.KOSCC25B cells. The CXCR7 down-regulated OSCC cells grew significantly slower than the negative control siRNA transfected KOSCC25B cells (p<0.05). Additionally, migration of si.KOSCC25B cells decreased significantly compared with non-transfected KOSCC25B cells (p<0.007). These results suggest that down-regulation of CXCR7 induces anti-proliferative and anti-migratory effects in OSCC, and that CXCR7 may be a useful target molecule for the treatment of OSCC.

Radiotherapy (RT) is a mainstay in the treatment of head and neck squamous cell carcinoma (HNSCC). For locally advanced HCSCC, concurrent chemoradiotherapy (CCRT) benefits HCSCC patients in terms of better survival and loco-regional control. In this study, we evaluated changes in oral microbiota in patients, who received CCRT for head and neck cancer. Oral rinsed samples were weekly collected before and during CCRT and at 4 weeks following treatment from HNSCC patients, who had received 70 Gy of radiation delivered to the primary sites for over 7 weeks and concurrent chemotherapy. Oral microbiota changes in three patients were analyzed by next-generation sequencing using 16S rRNA 454 pyrosequencing. On an average, 15,000 partial 16S rRNA gene sequences were obtained from each sample. All sequences fell into 11 different bacterial phyla. During early CCRT, the microbial diversity gradually decreased. In a patient, who did not receive any antibiotics during the CCRT, Firmicutes and Proteobacteria were the most abundant phylum. During the early CCRT, proteobacteria gradually decreased while Firmicutes increased. During the late CCRT, firmicutes gradually decreased while Bacteroides and Fusobacteria increased. In all the patients, yellow complex showed a gradual decrease, while orange and red complex showed a gradual increase during the CCRT. At 4 weeks after CCRT, the recovery of oral microbiota diversity was limited. During CCRT, there was a gradual increase in major periodontopathogens in association with the deterioration of the oral hygiene. Henceforth, it is proposed that understanding oral microbiota shift should provide better information for the development of effective oral care programs for patients receiving CCRT for HNSCC.