Yuichiro Imai

High LET radiation enhances apoptosis in mutated p53 cancer cells through Caspase-9 activation.

Although mutations in the p53 gene can lead to resistance to radiotherapy, chemotherapy and thermotherapy, high linear energy transfer (LET) radiation induces apoptosis regardless of p53 gene status in cancer cells. The aim of this study was to clarify the mechanisms involved in high LET radiation‐induced apoptosis. Human gingival cancer cells (Ca9‐22 cells) containing a mutated p53 (mp53) gene were irradiated with X‐rays, C‐ion (13–100 KeV/µm), or Fe‐ion beams (200 KeV/µm). Cellular sensitivities were determined using colony forming assays. Apoptosis was detected and quantified with Hoechst 33342 staining. The activity of Caspase‐3 was analyzed with Western blotting and flow cytometry. Cells irradiated with high LET radiation showed a high sensitivity with a high frequency of apoptosis induction. The relative biological effectiveness (RBE) values for the surviving fraction and apoptosis induction increased in a LET‐dependent manner. Both RBE curves reached a peak at 100 KeV/µm, and then decreased at values over 100 KeV/µm. When cells were irradiated with high LET radiation, Caspase‐3 was cleaved and activated, leading to poly (ADP‐ribose) polymerase (PARP) cleavage. In addition, Caspase‐9 inhibitor suppressed Caspase‐3 activation and apoptosis induction resulting from high LET radiation to a greater extent than Caspase‐8 inhibitor. These results suggest that high LET radiation enhances apoptosis by activation of Caspase‐3 through Caspase‐9, even in the presence of mp53. (Cancer Sci 2008; 99: 1455–1460)

Association between soluble MICA levels and disease stage IV oral squamous cell carcinoma in Japanese patients

The soluble form of major histocompatibility complex class I-related chain A (MICA) is released from the surface of tumor cells of epithelial origin. Although MICA expressed on the cell surface stimulates the immunoreceptor natural killer (NK) group 2, member D (NKG2D), the secreted form downregulates NKG2D activity, thus allowing the tumor to escape immunosurveillance by NKG2D-expressing cells. In this study, we examined the association between serum levels of soluble MICA and the severity of disease in patients with oral squamous cell carcinoma (OSCC). We used enzyme-linked immunoabsorbent assay to measure serum levels of soluble MICA in OSCC patients and normal control individuals. Among patients categorized according to most disease parameters tested (tumor size, location, grade of differentiation, regional lymph node status, disease stage), soluble MICA levels in sera did not statistically differ from those in normal control individuals. Patients with stage IV disease and/or regional lymph node metastasis did, however, exhibit significantly higher serum levels of soluble MICA than control individuals (95% confidence interval (CI), 0.65-2.45, p = 0.021, and 95% CI, 0.62-4.42, p = 0.031, respectively). Overall survival rates were significantly higher for OSCC patients with low soluble MICA levels (<50 pg/ml) than for those with high soluble MICA levels (>50 pg/ml) (95% CI, 0.43-2.75, p = 0.03). Serum levels of soluble MICA may be useful in the diagnosis of advanced stage OSCC and as an indicator of regional lymph node metastasis.

Relationship between soluble MICA and the MICA A5.1 homozygous genotype in patients with oral squamous cell carcinoma.

NK and cytotoxic T cells play an important role in the elimination of virus-infected and tumor cells through NKG2D activating receptors, which can promote the lysis of target cells by binding to the major histocompatibility complex class I-related chain A (MICA) proteins. Polymorphisms in MICA may influence its binding to the NKG2D. The soluble form of MICA is released from the surface of tumor cells of epithelial origin. Whereas MICA expressed on the cell surface stimulates the immunoreceptor natural killer group 2, member D (NKG2D), the secreted form down-regulates NKG2D activity, thus allowing the tumor to escape immunosurveillance by NKG2D-expressing cells. In this study, we examined the association between MICA gene microsatellite polymorphisms and serum levels of soluble MICA in patients with oral squamous cell carcinoma (OSCC). We found that patients with OSCC were more likely to have the A5.1 allele when compared to healthy subjects and also more likely to be homozygous for this allele (p=0.041). Patients with the homozygous A5.1 genotype had higher levels of soluble MICA (p=0.031) and a lower survival rate (p=0.026).

Preoperative concurrent chemoradiotherapy for stages II–IV oral squamous cell carcinoma: a retrospective analysis and the future possibility of this treatment strategy

This study evaluated survival in 154 patients with stages II-IV oral squamous cell carcinoma (OSCC) treated with preoperative concurrent chemoradiotherapy and assessed the future use of this treatment strategy. 14 patients exhibited advanced stage II, 73 exhibited stage III and 67 exhibited stage IV. All patients received 40Gy irradiation and concurrent cisplatin-based chemotherapy in two courses. Radical surgery was undertaken after 2-6 weeks. The clinical tumour response, histopathologic regression grade, residual tumour grade (RGrade) in the primary tumour and the level of residual pN+ were associated with prognosis. 90% of patients with complete response and 73% of patients with good partial response in the primary tumour were RGrade 0 (no residual tumour cells) or RGrade 1 (viable tumour cells remained within central superficial portion). In patients with complete response in the neck, residual pN+ was only seen in levels IB (8%) and IIA (8%); the higher the level of residual pN+, the lower the survival rate (p<0.0001). This treatment strategy was excellent for stages II-IV OSCC. It may be possible to perform minimally invasive surgery in which the extent of resection in primary tumour and neck is reduced in patients who achieve good response following preoperative chemoradiotherapy.

Mandibular reconstruction with vascularised fibular osteocutaneous flaps using prefabricated stereolithographic mandibular model

modifications to avoid transverse scars. The resulting method is very simple because it requires no manipulation of flaps. Tight stitches are essential for prevention of scar widening, however, if that should occur then later correction is facilitated by the straight line of closure. Further follow-up is necessary, however the initial scar contracture is minimal in comparison with other conventional methods after more than one year follow-up.

Depression of p53-independent Akt survival signals in human oral cancer cells bearing mutated p53 gene after exposure to high-LET radiation

Although mutations and deletions in the p53 tumor suppressor gene lead to resistance to low linear energy transfer (LET) radiation, high-LET radiation efficiently induces cell lethality and apoptosis regardless of the p53 gene status in cancer cells. Recently, it has been suggested that the induction of p53-independent apoptosis takes place through the activation of Caspase-9 which results in the cleavage of Caspase-3 and poly (ADP-ribose) polymerase (PARP). This study was designed to examine if high-LET radiation depresses serine/threonine protein kinase B (PKB, also known as Akt) and Akt-related proteins. Human gingival cancer cells (Ca9-22 cells) harboring a mutated p53 (mp53) gene were irradiated with 2 Gy of X-rays or Fe-ion beams. The cellular contents of Akt-related proteins participating in cell survival signaling were analyzed with Western Blotting 1, 2, 3 and 6h after irradiation. Cell cycle distributions after irradiation were assayed with flow cytometric analysis. Akt-related protein levels decreased when cells were irradiated with high-LET radiation. High-LET radiation increased G(2)/M phase arrests and suppressed the progression of the cell cycle much more efficiently when compared to low-LET radiation. These results suggest that high-LET radiation enhances apoptosis through the activation of Caspase-3 and Caspase-9, and suppresses cell growth by suppressing Akt-related signaling, even in mp53 bearing cancer cells.

Volumetric Fibular Transfer Planning With Shape-Based Indicators in Mandibular Reconstruction

In preoperative planning for mandibular reconstructive surgery, it is necessary to determine the osteotomy lines for fibular shaping and the proper placement of fibular segments in the mandible. Although virtual surgical planning has been utilized in preoperative decision making, current software designs require manual operation and a trial-and-error process to refine the reconstruction plan. We have developed volumetric fibular transfer simulation software that can quickly design a preoperative plan based on direct volume manipulation and quantitative comparison with the patients original mandible. We propose three quantitative shape indicators-volume ratio, contour error, and maximum projection-for symmetrical lesions of the mandible, and have implemented a parallel computation algorithm for the semiautomatic placement of fibular segments. Using this virtual planning software, we conducted a retrospective study of the computed tomography data from nine patients. We found that combining direct volume manipulation with real-time local search of placement improved the applicability of the planning system to optimize mandibular reconstruction.

Protein microarray analysis of apoptosis-related protein expression following heat shock in human tongue squamous cell carcinomas containing different p53 phenotypes

Purpose: Hyperthermia is useful in the treatment of human head and neck cancers, because it is relatively easy to regulate temperatures when compared to tumors located in deep organs. In this study, attention was focused on p53 as a possible predictive indicator for the efficacy of hyperthermic cancer therapy. Methods: Two kinds of cell lines were used. These were derived from a human squamous cell carcinoma (SAS) and had identical genetic backgrounds except for their p53 gene status. It was previously reported that the heat sensitivity and frequency of apoptosis in wild-type p53 cells (SAS/neo) were clearly elevated when compared with mutated p53 cells (SAS/mp53). In order to study the expression of apoptosis related proteins after heat treatment, protein microarray analysis was used. Results: The expression of apoptosis inhibitory proteins such as Bcl-2, Bcl-xL, NF-κB, COX2, STAT3, IL-6, and IKKα/1 was seen to increase after heat treatment in SAS/mp53 cells, but not in SAS/neo cells. Conclusion: The result of these observations indicates that apoptosis inhibitory proteins (such as Bcl-2, Bcl-xL, IL-6, etc.) were highly induced in SAS/mp53 cells after heat treatment when compared to control SAS/neo cells.

Risks of postextraction bleeding after receiving direct oral anticoagulants or warfarin: a retrospective cohort study

Objective The effect of direct oral anticoagulants (DOACs) on the risk of bleeding after tooth extraction remains unclear. This study aimed to evaluate the incidence of postextraction bleeding among patients who received DOAC and vitamin K antagonists (VKAs), such as warfarin. Design This study was a retrospective cohort analysis. Incidence rates and propensity score-matched regression models were used to compare the risks of bleeding after tooth extractions involving DOACs and VKAs. Setting The study took place in a single university hospital in Japan. Participants Between April 2013 and April 2015, 543 patients underwent a total of 1196 simple tooth extractions. Primary outcome measure The primary outcome measure was the occurrence of postextraction bleeding, which was defined as bleeding that could not be stopped by biting down on gauze and required medical treatment between 30 min and 7 days after the extraction. Results A total of 1196 tooth extractions (634 procedures) in 541 patients fulfilled the study criteria, with 72 extractions (41 procedures) involving DOACs, 100 extractions (50 procedures) involving VKAs and 1024 extractions (543 procedures) involving no anticoagulants. The incidences of postextraction bleeding per tooth for the DOAC, VKA and no anticoagulant extractions were 10.4%, 12.0% and 0.9%, respectively. The incidences of postextraction bleeding per procedure for DOACs, VKAs and no anticoagulants were 9.7%, 10.0% and 1.1%, respectively. In comparison to the VKA extractions, the DOAC extractions did not significantly increase the risk of postextraction bleeding (OR 0.69, 95% CIs 0.24 to 1.97; p=0.49). Conclusions The risk of postextraction bleeding was similar for DOAC and VKA extractions.

Fate of developing tooth buds located in relation to mandibular fractures in three infancy cases

The fate of developing tooth buds located in relation to mandibular fractures was investigated in three infancy cases. Three infants, 2 girls and a boy, aged from 1 year and 5-months old to 2 years and 6-months old, were treated for dislocated mandibular fracture in the symphyseal region by manual reduction and fixation with a thermoforming splint and circumferential wiring under general anesthesia. Fracture healing was uneventful in all cases. A few years later, no obvious deformity of the jaw or malocclusion was observed; however, malformation of the crown was found in one of the permanent teeth on the fracture line in the first case. In the second case, no abnormality was observed in one of the permanent teeth on the fracture line, but the effect on the other tooth could not be evaluated due to abnormality of the tooth probably not related to the injury. In the third case, root formation was arrested in one of the permanent teeth on the fracture line and the tooth was lost early after eruption. The development of tooth buds on the fracture line is not predictable and therefore, should be monitored by regular follow up.