Yoon La Choi

The enhanced reactivity of endogenous biotin-like molecules by antigen retrieval procedures and signal amplification with tyramine

In diagnostic pathology and immunocytochemical research, immunohistochemical techniques using the streptavidin–biotin–peroxidase system have played an extremely valuable role. This system, based on the high affinity of streptavidin for biotin, may, however, provoke false positive results because of endogenous streptavidin-binding sites in human tissues. With the advent of the antigen retrieval procedure and signal amplification method, this problem can be serious enough to cause mistakes in interpreting immunohistochemical staining results. Therefore, we examined the distribution of endogenous biotin-like molecules in various human tissues and the influence of various antigen retrieval procedures with or without signal amplification using biotinylated tyramine to reveal these biotin-like activities. We observed that endogenous biotin-like molecules were present in a wide range of tissues, and their activity was markedly enhanced by employing antigen retrieval procedures or signal amplification. Furthermore, the extent to which the activity of endogenous biotin-like activities was enhanced depended on the kinds of antigen retrieval procedures and signal amplification employed. Pressure cooking and tyramine amplification with microwave heating showed the highest activities. These results show that the antigen retrieval procedures and signal amplification with tyramine can enhance the activity of endogenous biotin or biotin-like molecules as well as antigenicity, which can be a pitfall in the interpretation of immunohistochemical data.

Spinal intramedullary lipoma: report of three cases

Study design: Case report.Objective: To report three cases of spinal intramedullary lipoma seen in the last 10 years and present the clinical characteristics and surgical outcome of these cases.Method: Two patients were boys aged 12 years and 7 months, respectively. The other was a female patient aged 6 months. Chief complaints were hemiparesis, back swelling and thoracic scoliosis. All patients were diagnosed with magnetic resonance images. The lesion was located in the cervico-thoracic spine (foramen magnum to T1) in one case, thoracic spine (T9−T12) with the back swelling at L2-4 level in the second, and in the third, one mass extended from C6 to T11 and the other mass was located in the L1-2 level, separately.Result: All masses were removed subtotally and dysraphism was absent. Postoperatively, neurological status of the first and the second patient were unchanged, but in the third case weakness was transiently aggravated.Conclusion: Intramedullary lipoma is a rare spinal lesion and multiple intramedullary lipoma is extremely rare. Treatment principle is surgical decompression before symptom progression. Laminoplastic laminotomy is an appropriate approach for decompression of an intramedullary lipoma.

High level of CDK4 amplification is a poor prognostic factor in well-differentiated and dedifferentiated liposarcoma.

The amplification of MDM2 and CDK4 is the main molecular feature of well-differentiated liposarcomas (WDLS) and dedifferentiated liposarcomas (DDLS). Although the diagnostic usefulness of this molecular characteristic in liposarcomas has been investigated, its prognostic utility of quantitative gene level has not been explored. The aim of this study was to assess the prognostic significance of level of CDK4 amplification in MDM2-amplified WDLS/DDLS. MDM2 amplification in liposarcomas was confirmed by fluorescence in situ hybridization. The copy number of MDM2 and CDK4 was further determined by quantitative PCR (qPCR) and multiplex ligation-dependent probe amplification. Among 56 MDM2-amplified liposarcomas, 30 cases were assigned as WDLS, and 26 as DDLS. When liposarcomas were classified by qPCR-determined CDK4 amplification levels, the high-CDK4 group showed significantly poorer progression free survival (P=0.001) and disease specific survival (P=0.033) than the low-CDK4 group. However, MDM2 amplification level did not show prognostic significance. In WDLS/DDLS, the level of CDK4 amplification was useful for prognosis prediction and precise stratification of patients for targeted therapy.

Targeted cytotoxic effect of anti-JL1 immunotoxin against a human leukemic cell line and its clinical implications

We have previously reported the identification of a unique thymocyte-specific surface molecule, JL1, which was detected using the monoclonal antibody (mAb), anti-JL1. Interestingly, JL1 was shown to be expressed in most leukemias, irrespective of their immunophenotype, and subpopulations of normal bone marrow (BM) mononuclear cells (MNCs). Here we investigated the potential usefulness of the anti-JL1 mAb as a therapeutic tool for leukemia. We demonstrated that the proliferation of cultured human leukemia cells was dramatically inhibited in vitro by anti-JL1 mAb conjugated with the polypeptide toxin, gelonin, but not by gelonin alone. We then systematically investigated the reactivity of the anti-JL1 mAb against normal human tissues to evaluate possible side effects along with various hematopoietic and nonhematopoietic tumor cell lines. All of 33 types of normal tissues except thymus and subpopulation of BM MNCs were clearly devoid of JL1 expression. Among tumor cell lines, all the nonhematopoietic cell lines tested were negative for JL1 expression, while some hematopoietic cell lines contained JL1 antigen. Collectively, the results showed the cytotoxic effects of anti-JL1-based immunotoxin against JL1-positive leukemic cells, sparing most normal tissues other than thymocytes and some BM MNCs. Therefore, we strongly suggest that gelonin-conjugated anti-JL1 mAb immunotoxin could be developed as a potential immunotherapeutic agent in the treatment of various types of JL1-positive acute leukemias.

A case of recurrent subependymoma with subependymal seeding: case report.

Subependymoma is a rare, slow growing, rarely recurrent tumor. We report a case of recurrent subependymoma with subependymal seeding. An intraventricular tumor in the left temporal horn was detected in a 48-year-old female who presented with a 4-year history of dizziness and memory disturbance. Following near total surgical resection, a tumor diagnosis of subependymoma was confirmed by scattered clusters of isomorphic nuclei embedded in a dense fibrillary matrix of glial cell processes. Twenty-six months after surgery, follow-up (F/U) magnetic resonance (MR) imaging revealed tumor recurrence in the previous site which necessitated linear accelerator radiosurgery (LINAC). A further 21 months later, F/U MR imaging showed recurrent, multiple, enhanced, nodular lesions in the enlarged left lateral ventricle for which the patient underwent reoperation. Radiological and operative findings revealed local relapse with subependymal seeding. The pathological finding was similar to that of the previous tumor and compatible with subependymoma. The patient underwent radiation therapy for the residual tumor. This case history suggests that symptomatic residual tumors require close observation even though the clinical course of subependymoma is usually benign.