Eiji Yumoto

Presenilin-dependent γ-secretase activity mediates the intramembranous cleavage of CD44

CD44 is the major adhesion molecule for the extracellular matrix components and is implicated in a wide variety of physiological and pathological processes including the regulation of tumor cell growth and metastasis. Our previous studies have shown that CD44 undergoes sequential proteolytic cleavages in the extracellular and transmembrane domains and the cleavage product derived from CD44 intramembranous cleavage acts as a signal transduction molecule. However, the underlying mechanism of the intramembranous cleavage of CD44 remains to be elucidated. In the present study, we report for the first time that CD44 is a substrate of the presenilin (PS)-dependent γ-secretase. We demonstrate that the intramembranous cleavage of CD44 induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment or mechanical scraping is blocked by γ-secretase inhibitors in U251MG cells and that this cleavage is also inhibited in PS-deficient mouse embryonic fibroblasts. Furthermore, we showed that PS1 is redistributed to ruffling areas of the plasma membrane similarly to CD44 after TPA treatment, supporting our biochemical observation that PS1 is involved in the intramembranous cleavage of CD44. Our present findings suggest important implications for understanding CD44-dependent signal transduction and a potential role of PS/γ-secretase activity in the functional regulation of adhesion molecules.

Genetic diagnosis of micrometastasis based on SCC antigen mRNA in cervical lymph nodes of head and neck cancer

This study is designed to assess gene expression of squamous cell carcinoma antigen (SCCA) mRNA to detect micrometastases in cervical lymph nodes (LNs) of head and neck cancer. We examined the expression of SCCA mRNA in 12 primary tumors and 212 cervical LNs (101 LNs taken from 8 patients with tongue cancer, 71 from 7 patients with gingival cancer, 19 from 2 patients with laryngeal cancer, 9 from 2 patients with pharyngeal cancer, 7 from 1 patient with cancer of the buccal mucosa, and 5 from 1 patient with cancer of floor of the mouth). Detectability of metastatic LNs by nested and single reverse transcriptase-polymerase chain reaction (RT-PCR) was compared with semiserial sections (hematoxylin-eosin staining and keratin immunostaining). All primary tumors expressed SCCA mRNA. Of 198 histologically metastasis-negative nodes, SCCA mRNA was detected in 37 (18.7%) by nested PCR. Eleven micrometastatic foci in 9 LNs (4.6%) were discovered by semiserial sectioning. This suggests that SCCA mRNA is a promising tumor marker for detecting the micrometastases in cervical LNs of head and neck cancer.

Clinical significance of p53 functional loss in squamous cell carcinoma of the oropharynx

We examined the frequency of p53 mutations in 38 oropharyngeal squamous cell carcinomas (SCC), using both a yeast functional assay and a conventional immunohistochemical staining method (IHC) to detect p53 mutations.We also explored the clinical importance of p53 mutations in oropharyngeal SCC. An accumulation of p53 protein was detected in 17 of the 38 (45%) tumors by IHC, whereas the yeast‐based assay detected 6 additional p53 mutations, for a total of 23 tumors (61%) with p53 mutations. The cDNA sequencing analysis revealed that the 6 mutations undetected by IHC consisted of 3 frameshift, 1 nonsense and 2 missense mutations. Thus, the yeast functional assay was more sensitive than conventional IHC for detecting p53 mutations. Subsequently, the relationship between p53 mutations and the clinico‐pathological parameters in oropharyngeal SCC was evaluated using the results of the functional assay. Mutation of p53 was not associated with the patient age, sex, tumor stage or degree of tumor cell differentiation. Interestingly, heavy drinking had a significant positive correlation with the p53 mutation, but heavy smoking did not, suggesting that prolonged exposure to alcohol is more related to p53 mutation in oropharyngeal SCC than to tobacco consumption. Radiation sensitivity was examined by comparing tumor size on magnetic resonance images before and after completion of therapy with 45 Gy radiation, in the 18 cases of T2 oropharyngeal SCC that were initially treated by radiotherapy. The results showed that tumors with wild‐type p53 decreased in size significantly compared to those with mutant p53. In 33 patients treated with curative intent, the overall survival after the completion of therapy was better in patients with a wild‐type p53 tumor than in patients with a mutant p53 tumor. We conclude that p53 mutation is associated with radiation resistance and a decreased probability of survival in oropharyngeal SCC. Int. J. Cancer (Pred. Oncol.) 89:187–193, 2000.

Immediate Recurrent Laryngeal Nerve Reconstruction and Vocal Outcome

Objective: The objective of this prospective study was to assess the long‐term effects of immediate reconstruction of the recurrent laryngeal nerve (RLN) during thyroid cancer extirpation on postoperative phonatory function.

Causes of recurrent laryngeal nerve paralysis

OBJECTIVE Persistent hoarseness due to recurrent laryngeal nerve paralysis (RLNP) reduces the quality of life unless it is adequately treated. This study examined the indications for phonosurgical intervention in patients with RLNP. MATERIALS AND METHODS The medical records of the Ehime University Hospital, Ehime, Japan, from October 1976 until December 1997 were reviewed retrospectively to identify patients with RLNP. The data collected included age, gender, paralyzed side, and cause of paralysis. RESULTS Four hundred and sixty-six patients with RLNP were identified: 262 males and 204 females. Unilateral RLNP was present in 422 patients, while 44 presented with bilateral RLNP. The incidence was relatively high in the 7th and 8th decades, and was twice as high in male patients as in female patients. The 466 patients were divided into 2 groups: Group 1 included 225 patients seen before January 1987, and Group 2 included 241 patients seen after this date. The number of patients with postoperative RLNP was significantly higher in Group 2 (124 of 239 patients) than in Group 1 (65 of 227 patients) (P<0.05). Surgery for cardiovascular disease, esophageal cancer, and skull base and thyroid gland tumors contributed to this increased incidence of postoperative RLNP. CONCLUSIONS Patients with persistent unilateral RLNP require appropriate treatment for hoarseness, regardless of its cause. Since the incidence of RLNP related to surgery was significantly increased in Group 2, phonosurgery has become more important for improving the quality of life of these patients.

Effect of sinus surgery on visual disturbance caused by spheno-ethmoid mucoceles

Fifteen patients suffering from visual disturbance of varying degrees caused by a mucocele of the posterior ethmoid and/or sphenoid sinuses underwent marsupialization of a mucocele into the nasal cavity. Five of the eight patients with severe visual loss worse than 20/200 showed recovery of measurable vision. Two of these five were operated on within 24 hours after the onset of visual loss and showed marked recovery to 20/25 and 20/15. The other seven patients who had relatively mild visual disturbance experienced improvement of visual acuity or remission of subjective complaints such as blurred vision postoperatively. During operation partial bony defect was found in the optic canal in 12 patients and in the skull base in 12 patients. A good understanding of this disease by ophthalmologists and otolaryngologists is essential for early diagnosis and prompt surgical treatment to avoid permanent visual dysfunction and operative sequelae.

Sino‐Orbital aspergillosis associated with total ophthalmoplegia

Invasive aspcrgillosis of the paranasal sinuses involving the orbit is termed sino‐orbital aspergillosis. Prognosis of sino‐orbital aspergillosis, complicated by impaired visual acuity and neurological signs, is disastrous and usually fatal. We herein report two patients with sino‐orbital aspergillosis associated with total ophthalmoplegia. One patient was successfully treated with surgical eradication including orbital exenteration. In contrast, the other died of cerebral infarction, probably due to fungal thrombosis of the middle cerebral artery, despite repeated local debridement followed by orbital exenteration and administration of antifungal agents. Experience with these cases strongly indicates the necessity of prompt surgical eradication, including orbital exenteration if necessary, in the treatment of sino‐orbital aspergillosis.

Three‐Dimensional Endoscopic Mode for Observation of Laryngeal Structures by Helical Computed Tomography

We produced high‐quality three‐dimensional (3D) endoscopic images of the larynx using helical scanning computed tomography. Subjects included two normal volunteers and 10 patients: five with laryngeal cancer, four with unilateral recurrent laryngeal nerve (RLN) palsy, and one with atrophied vocal folds. Two vertically split hemilaryngeal images were displayed together with the oral and tracheal views. Although motion artifacts were seen in four patients, laryngeal structures including the vocal fold, ventricular fold, and ventricle were clearly identified in all subjects. In the patients with cancer, axial images showing the extent of the tumor in each patient provided more information than 3D endoscopic images. In the patients with RLN palsy and atrophied vocal fold, combination of 3D endoscopic and cross‐sectional images offered more diagnostic information than axial images alone.

Transmandibular Transpterygoid Approach to the Nasopharynx, Parapharyngeal Space, and Skull Base

The nasopharynx, upper part of the parapharyngeal space, and skull base are relatively inaccessible to the surgeon without major postoperative complications. Operative fields reached by conventional approaches through the palate and maxillary sinus are too limited and narrow to remove extensive tumors. The authors applied a transmandibular transpterygoid approach for the removal of five residual nasopharyngeal carcinomas (NPCs) after full doses of irradiation, one pleomorphic adenoma of the nasopharynx, and one large parapharyngeal schwannoma extending into the jugular foramen. This approach offers a wide operative field so that large blood vessels and cranial nerves can be managed easily. All tumors were successfully resected. Two patients with benign neoplasms had uneventful recoveries after treatment. Of five patients with NPC, two are alive with no evidence of disease for 68 months and 50 months, respectively, while two died of metastases to the liver and bones. The other patient is alive with metastases in the lungs. No tumor recurred in the local primary site, however. Since the number of NPC cases is small, the usefulness of surgical removal of the postirradiation residual NPC is not clear. Our experience proved that the transmandibular transpterygoid approach is a practical method in the treatment of neoplastic lesions in the nasopharynx, parapharyngeal space, and skull base.

Mouse Otocyst Transuterine Gene Transfer Restores Hearing in Mice With Connexin 30 Deletion-associated Hearing Loss

Although numerous causative genes for hereditary hearing loss have been identified, there are no fundamental treatments for this condition. Herein, we describe a novel potential treatment for genetic hearing loss. Because mutations or deletions in the connexin (Cx) genes are common causes of profound congenital hearing loss in both humans and mice, we investigated whether gene supplementation therapy using the wild-type Cx gene could cure hearing loss. We first generated inner ear-specific connexin 30 (Cx30)-deficient mice via the transuterine transfer of Cx30-targeted short hairpin RNA (shRNA-Cx30) into otocysts. The inner ear-specific Cx30-deficient mice mimicked homozygous Cx30-deficient mice both histologically and physiologically. Subsequently, we cotransfected the shRNA-Cx30 and the wild-type Cx30 gene. The cotransfected mice exhibited Cx30 expression in the cochleae and displayed normal auditory functions. Next, we performed the transuterine transfer of the wild-type Cx30 gene into the otocysts of homozygous Cx30-deficient mice, thereby rescuing the lack of Cx30 expression in the cochleae and restoring auditory functioning. These results demonstrate that supplementation therapy with wild-type genes can restore postnatal auditory functioning. Moreover, this is the first report to show that Cx-related genetic hearing loss is treatable by in vivo gene therapy.