Insulin-like growth factor-I and over-expression of Bcl-xL prevent glucose-mediated apoptosis in Schwann cells

Schwann cells (SCs), the myelinating cells of the peripheral nervous system, are lost or damaged in patients suffering from diabetic neuropathy. In the current study, 2 model systems are used to study the mechanism of SC damage in diabetic neuropathy: the streptozotocin (STZ)-treated diabetic rat and cultures of purified SCs in vitro. Electron microscopy of dorsal root ganglia from STZ-treated rats reveals classic ultrastructural features of apoptosis in SCs, including chromatin clumping and prominent vacuolation. Bisbenzamide staining of SCs cultured in hyperglycemic defined media shows nuclear blebbing of apoptotic cells. Insulin-like growth factor-I (IGF-I) is protective. LY294002, a phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, blocks the effect of IGF-I. High glucose induces caspase cleavage in apoptotic SCs--an effect that is blocked by bok-asp-fmk (BAF), a caspase inhibitor. Although Bcl-xL expression remains unchanged in experimental conditions, over-expression of Bcl-xL protects SCs from apoptosis. In summary, hyperglycemia induces caspase activation and morphologic changes in SCs consistent with apoptotic death, both in vivo and in vitro. Over-expression of Bcl-xL, or IGF-I, signaling via PI 3-kinase, protects SCs from glucose-mediated apoptosis in vitro. IGF-I may be useful in preventing hyperglycemia-induced damage to SCs in patients suffering from diabetic neuropathy.

Insulin-like growth factor-I and Bcl-X(L) inhibit c-jun N-terminal kinase activation and rescue Schwann cells from apoptosis

We previously reported that Schwann cells undergo apoptosis after serum withdrawal. Insulin-like growth factor-I, via phosphatidylinositol-3 kinase, inhibits caspase activation and rescues Schwann cells from serum withdrawal-induced apoptosis. In this study, we examined the role of c-jun N-terminal protein kinase (JNK) in Schwann cell apoptosis induced by serum withdrawal. Activation of both JNK1 and JNK2 was detected 1 h after serum withdrawal with the maximal level detected at 2 h. A dominant negative JNK mutant, JNK (APF), blocked JNK activation induced by serum withdrawal and Schwann cell apoptosis, suggesting JNK activation participates in Schwann cell apoptosis. Serum withdrawal-induced JNK activity was caspase dependent and inhibited by a caspase 3 inhibitor, Ac-DEVD-CHO. Because insulin-like growth factor-I and Bcl-X(L) are both Schwann cell survival factors, we tested their effects on JNK activation during apoptosis. Insulin-like growth factor-I treatment decreased both JNK1 and JNK2 activity induced by serum withdrawal. LY294002, a phosphatidylinositol-3 kinase inhibitor, blocked insulin-like growth factor-I inhibition on JNK activation, suggesting that phosphatidylinositol-3 kinase mediates the effects of insulin-like growth factor-I. Overexpression of Bcl-X(L) also resulted in less Schwann cell death and inhibition of JNK activation after serum withdrawal. Collectively, these results suggest JNK activation is involved in Schwann cell apoptosis induced by serum withdrawal. Insulin-like growth factor-I and Bcl family proteins rescue Schwann cells, at least in part, by inhibition of JNK activity.

Expression of nm23-H1 in transitional cell carcinoma of the upper urinary tract

Transitional cell carcinoma of the upper urinary tract is an uncommon neoplasm. Relatively little information is available regarding the clinical relevance of molecular markers. This study was performed to examine the importance of nm23-H1 gene expression (NM23-H1) in this type of tumors. Immunohistochemical expression of NM23-H1 was analyzed in 90 cases of upper urinary tract cancer, and was compared for its prognostic significance with conventional biological indicators. High expression of NM23-H1 was found in 7 cases (8%), intermediate expression in 32 cases (36%), and low expression in 51 cases (57%). Reduced NM23-H1 (defined as intermediate or low level of expression) was associated with a higher histological grading (p=0.002), invasive tumor growth (p=0. 002), or an increased proliferating cell nuclear antigen labeling index (p=0.004). NM23-H1 tended to inversely relate to later recurrence or long-term survival (p=0.06), but, only tumor staging was found to be significant in predicting clinical outcome (p=0.002). nm23-H1 appears to function as a tumor suppressor for upper urinary tract cancer, however, evaluation of NM23-H1 provides limited prognostic information.

Analysis of synthetic chemical drugs in adulterated Chinese medicines by capillary electrophoresis/electrospray ionization mass spectrometry

Sixteen synthetic chemical drugs, often found in adulterated Chinese medicines, were studied by capillary electrophoresis/UV absorbance (CE/UV) and capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS). Only nine peaks were detected with CZE/UV, but on-line CZE/MS provided clear identification for most compounds. For a real sample of a Chinese medicinal preparation, a few adulterants were identified by their migration times and protonated molecular ions. For coeluting compounds, more reliable identification was achieved by MS/MS in selected reaction monitoring mode. Micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) provided better separation than capillary zone electrophoresis (CZE), and, under optimal conditions, fourteen peaks were detected using UV detection. In ESI, the interference of SDS was less severe in positive ion mode than in negative ion mode. Up to 20 mM SDS could be used in direct coupling of MEKC with ESI-MS if the mass spectrometer was operated in positive ion mode. Because of better resolution in MEKC, adulterants can be identified without the use of MS/MS.

IGF-I promotes Schwann cell motility and survival via activation of Akt

We previously reported insulin-like growth factor-I (IGF-I) promotes Schwann cell (SC) motility and rescues SC from apoptosis induced by serum deprivation. This effect is mediated by phosphatidylinositol-3 (PI-3) kinase. In the current study, we examined the role of Akt, a downstream kinase of PI-3K, in SC motility and IGF-I mediated protection from apoptosis. IGF-I induces Akt phosphorylation at Ser473, an event which may be blocked by pretreatment with a PI-3K inhibitor, LY294002. In dominant negative K179M Akt (K179M) transfected SC, however, Akt is not activated in response to IGF-I. In addition, IGF-I is unable to promote SC motility and survival in K179M SC. These results suggest a critical role for Akt in IGF-I mediated motility and survival in SC.

GTPases and phosphatidylinositol 3-kinase are critical for insulin-like growth factor-I-mediated Schwann cell motility

Previously, we reported insulin-like growth factor-I (IGF-I) promotes motility and focal adhesion kinase (FAK) activation in neuronal cells. In the current study, we examined the role of IGF-I in Schwann cell (SC) motility. IGF-I increases SC process extension and motility. In parallel, IGF-I activates IGF-I receptor, insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3 (PI-3)-kinase, and FAK. LY294002, a PI-3 kinase inhibitor, blocks IGF-I-induced motility and FAK phosphorylation. The Rho family of GTPases is important in the regulation of the cytoskeleton. Overexpression of constitutively active Leu-61 Cdc42 and Val-12 Rac1 enhances SC motility which is unaffected by LY294002. In parallel, stable transfection of SC with dominant negative Asn-17 Rac1 blocks IGF-I-mediated SC motility and FAK phosphorylation, implying Rac is an upstream regulator of FAK. Collectively our results suggest that IGF-I regulates SC motility by reorganization of the actin cytoskeleton via the downstream activation of a PI-3 kinase, small GTPase, and FAK pathway.

Insulin-like growth factor-I promotes myelination of peripheral sensory axons

Insulin-like growth factor-I (IGF-I) in vivo or in the presence of other permissive factors can promote myelination in the central nervous system. In the current study, we examine the role of IGF-I in the myelination of peripheral nerves. In rat cocultures of dorsal root ganglia (DRG) and Schwann cells (SC) grown in serum- and insulin-free defined medium, IGF-I induces a dose dependent upregulation in myelin proteins such as P0, corresponding to maximal SC ensheathment. Furthermore, IGF-I is essential in promoting a dose-dependent, long-term myelination of DRG sensory axons. In the absence of IGF-I, axons and SC survive, but fail to myelinate. In the presence of 10 nM IGF-I, 59% of axons are myelinated at 21 days, whereas in the absence of IGF-I myelination fails to occur. Maximum SC ensheathment occurs 48 hours after addition of IGF-I. If IGF-I is withdrawn at 48 hours, axon segregation by SC persists, however, most axons and SC do not exhibit a one-to-one relationship and little myelination is observed. IGF-I is important in myelination and is critical not only for initial SC ensheathment of the axon and upregulation of myelin proteins, but also for sustained myelination. Furthermore, IGF-I associated axonal size is not the sole determinant for myelination.

The clinical value of p21WAF1/CIP1 expression in superficial bladder cancer

The clinical value of p21WAF1/CIP1 in superficial bladder cancer remains controversial. To address the question, we examined the expression patterns of p21 and p53 gene products and compared for their significance in a total of 89 cases of superficial (pTa/pT1) bladder cancer. Over-expression of p21 was detected in 32 of 89 (36%) tumors. But, the expression status did not correlate with biological indicators or clinical outcome (p > 0.1, respectively). Factors predicting clinical outcome were multiplicity for tumor recurrence (p = 0.0002) or patient survival (p = 0.03), and the histological grading for disease progression (p = 0.02) or patient survival (p = 0.05). Taking into account the p53 status, a trend approaching better prognosis for p53+p21+ tumors was observed compared with that of p53+p21- bladder cancer (p = 0.08). Our data indicate that evaluation of p21 status does not provide better prognostic information compared with conventional biological indicators of superficial bladder cancer. Maintenance of p21 appears to abrogate the deleterious effects of p53 alterations in the tumorigenesis of human bladder.

Transitional cell carcinoma in dialysis patients

OBJECTIVE

The aim of our study was to determine whether there is an increased incidence of urothelial cancer, especially transitional cell carcinoma (TCC), in uremic patients on dialysis.

METHODS

Retrospective chart analyses were completed for 1,910 uremic patients undergoing maintenance dialysis between January 1987 and December 1997. The incidence of urinary tract cancer was assessed. Only the patients with cancers diagnosed after start of dialysis were enrolled in the study.

RESULTS

Of the 1,910 patients, 70 had concomitant urinary tract cancers. Nineteen patients (0.99%), including 17 patients with TCC and 2 patients with renal cell carcinoma, were diagnosed after the initiation of dialysis. The average duration from dialysis to TCC diagnosis was 38.3 (range 2-144) months. Painless gross hematuria was the cardinal symptom in 16 of the 17 patients with TCC. In the 17 patients with TCC, no distant metastases were found at the time of diagnosis. Fourteen patients (82.3%) were stage 0 or A, and 1 patient was stage B1.

CONCLUSIONS

The 0.89% incidence of TCC in our dialysis patients was high as compared with that of the general population. The risks of developing urinary TCC in dialysis patients were examined, and we suggest that immunosuppressive stage, dialysis procedure, and chronic bladder irritation (decreased urinary wash effect) may play a part in the development of urinary TCC in dialysis patients. Early detection of hematuria due to regular visits and decreased exposure of urinary tract epithelium to carcinogens from urine may explain why early-stage TCC was seen in most of our patients.

Insulin-like growth factor-I prevents caspase-mediated apoptosis in Schwann cells

Both neurons and glia succumb to programmed cell death (PCD) when deprived of growth factors at critical periods in development or following injury. Insulin-like growth factor-I (IGF-I) prevents apoptosis in neurons in vitro. To investigate whether IGF-I can protect Schwann cells (SC) from apoptosis, SC were harvested from postnatal day 3 rats and maintained in serum-containing media until confluency. When cells were switched to serum-free defined media (DM) for 12-72 h, they underwent PCD. Addition of insulin or IGF-I prevented apoptosis. Bisbenzamide staining revealed nuclear condensation and formation of apoptotic bodies in SC grown in DM alone, but SC grown in DM plus IGF-I had normal nuclear morphology. The phosphatidylinositol 3-kinase (PI 3-K) inhibitor LY294002 blocked IGF-I-mediated protection. Caspase-3 activity was rapidly activated upon serum withdrawal in SC, and the caspase inhibitor BAF blocked apoptosis. These results suggest that IGF-I rescues SC from apoptosis via PI 3-K signaling which is upstream from caspase activation.

Regulation of insulin-like growth factor-binding protein-5 expression during Schwann cell differentiation

We have reported that immortalized Schwann cells (SC) express the insulin-like growth factor I receptor and IGF-binding protein-5 (IGFBP-5). IGF-I promotes SC survival and protects IGFBP-5 in SC-conditioned medium from proteolysis. In the current study we examined the roles of IGF-I and IGFBP-5 in primary SC. IGF-I enhances primary SC differentiation and gene and protein expression of IGFBP-5 and the myelinating protein, P0. SC that stably overexpress human IGFBP-5 also have higher levels of P0 gene expression. The phosphatidylinositol-3 kinase inhibitor (LY294002), but not the mitogen-activated protein kinase kinase inhibitor (PD98059), blocks IGF-I enhancement of IGFBP-5 gene and protein expression. Collectively, these results suggest that IGF-I promotes SC differentiation, and this may occur in part by enhancing IGFBP-5 expression via phosphatidylinositol-3 kinase activation. These data support a link between enhanced IGFBP-5 expression and cellular differentiation.

IGF-I promotes peripheral nervous system myelination

Insulin-like growth factor-I (IGF-I) promotes the proliferation and differentiation of Schwann cells (SC). We use SC/dorsal root ganglion neuron (DRG) cocultures to examine the effects of IGF-I on the interaction between axons and SC. As SC extend processes toward the axon in the presence of IGF-I, these processes attach to and ensheath axons. Continued IGF-I exposure leads to enhanced P0 expression and long-term myelination. No myelination occurs in the absence of IGF-I. These data imply that IGF-I is critical not only for SC attachment and ensheathment of axons but also for long-term myelination.

Expression of vascular endothelial growth factor in primary superficial bladder cancer

BACKGROUND

Angiogenesis is of vital importance during the development and progression of solid tumors. This study was performed to test the clinical significance of vascular endothelial growth factor (VEGF) expression in primary superficial bladder cancer.

MATERIALS AND METHOD

A cohort of 185 cases of pTa/pT1 transitional cell bladder cancer and six cases of normal urothelium were studied by immunohistochemistry. Expression of VEGF was correlated with biological indicators of bladder cancer and examined for their prognostic value.

RESULTS

Variable amounts of VEGF were detected in 35 cases (18.9%), with 17.9% and 20.3% in pTa and pT1 tumors respectively. There was a positive association of VEGF expression with histological grading (p = 0.03). Otherwise, no apparent correlation was observed with remaining biopathological indicators (p > 0.1, respectively). Risk factors in predicting tumor recurrence were multiple tumors at diagnosis and lamina propria invasion (p < 0.05, respectively). Patients with multiple tumors also had a lower survival rate than those with a solitary tumor (p = 0.0008). However, expression of VEGF was not correlated with risk of tumor recurrence or patient survival (p > 0.1).

CONCLUSIONS

Expression of VEGF is one of the characteristics of tumor dedifferentiation and may play a role in the development of a subset of superficial bladder cancer. Evaluation of VEGF expression dose not provide independent prognostic information for patients with superficial bladder cancer.

Caveolin-1 expression in Schwann cells

Caveolae are non-clathrin-coated invaginations of the plasma membrane, which are present in most cell types. An integral component of caveolae is the caveolin family of related proteins, which not only forms the structural framework of caveolae, but also likely subserves its functional roles, including regulation of signal transduction and cellular transport, in particular, cholesterol trafficking. Although caveolae have been identified ultrastructurally in the peripheral nervous system (PNS), caveolin expression has not previously been studied. To date, three caveolin genes have been reported. Here, we show for the first time that caveolin-1 is expressed by Schwann cells (SC) as well as several SC-derived cell lines. Caveolin-1 is enriched in the buoyant, detergent-insoluble membranes of rat sciatic nerve (SN) and SC, a hallmark of the caveolar compartment. Caveolin-1 exists as both soluble and insoluble forms in rat SN and SC, and localizes to SC cytoplasm and abaxonal myelin. SC caveolin-1 decreases after axotomy, when SC revert to a premyelinating phenotype. We speculate that caveolin-1 may regulate signal transduction and/or cholesterol transport in myelinating SC.

Endogenous casein kinase I catalyzes the phosphorylation of the lens fiber cell connexin49

The lens fiber cell-specific gap junction protein connexin49 is a substrate for a membrane-associated Ser/Thr protein kinase that can be extracted from lens cell membranes by 0.6 M KCl. However, the identity of this protein kinase has not been defined. In this report, evidence is presented indicating that it is casein kinase I. Thus, connexin49 was shown to be a substrate for purified casein kinase I but not for casein kinase II; the endogenous connexin49 protein kinase activity extracted from lens membranes with KCl was inhibited by the casein kinase I-specific inhibitor, N-(2-aminoethyl)-5-chloroisoquinoline-8-sulfonamide (CKI-7); the connexin49 protein kinase activity in the lens membrane KCl extract, which could be partially purified by gel filtration and affinity purification with a casein-Sepharose 4B column, copurified with casein kinase activity; phosphopeptide analysis showed that casein kinase I and the connexin49 protein kinase activity in the lens membrane KCl extract probably share the same phosphorylation sites in connexin49. Reverse transcription-PCR using total ovine lens RNA and casein kinase I isoform-specific oligonucleotide primers resulted in the amplification of cDNAs encoding casein kinase I-alpha and -gamma, while an in-gel casein kinase assay indicated casein kinase activity in the lens membrane KCl extract was associated with a major 39.2-kDa species, which is consistent with the 36 to 40-kDa size of casein kinase I-alpha in other animal species. These results demonstrate that the protein kinase activity present in the lens membrane 0.6 M KCl extract that catalyzes the phosphorylation of connexin49 is casein kinase I, probably the alpha isoform.

Laparoscopic wedge resection of benign gastric tumor

BACKGROUND/AIMS

In the past 2 years, 9 patients diagnosed as benign gastric tumor pre-operatively underwent laparoscopic wedge resection of stomach at National Taiwan University Hospital. Among them, 6 were females and 3 were males.

METHODOLOGY

Histopathologically, 7 of 9 cases were of gastrointestinal stromal tumor (GIST). The clinical characteristics of this group were retrospectively reviewed and compared with another 12 cases of benign gastric tumor receiving open wedge resection in the same period.

RESULTS

There were no differences in sex, age, and pre-operative diagnosis in these two groups. It took a significantly longer operation time in the laparoscopic group than it did in the open group (205.71 vs. 97.5 min, p<0.05). However, the patients of the laparoscopic group started post-operative oral intake earlier (4.0 vs. 5.58 days, p<0.05), had shorter hospital stays (6.67 vs. 10.77 days, p<0.05), and lower analgesic usage rate (55% vs. 100%). There were no differences in operative complication rates.

CONCLUSIONS

Laparoscopic resection of benign-gastric tumor is recommended as a minimally invasive procedure.

Insulin receptor substrate 2 and Shc play different roles in insulin-like growth factor I signaling

The major substrates for the type I insulin-like growth factor (IGF-I) receptor are Shc and insulin receptor substrate (IRS) proteins. In the current study, we report that IGF-I induces a sustained tyrosine phosphorylation of Shc and its association with Grb2 in SH-SY5Y human neuroblastoma cells. The time course of Shc tyrosine phosphorylation parallels the time course of IGF-I-stimulated activation of extracellular signal-regulated kinase (ERK). Transfection of SH-SY5Y cells with a p52 Shc mutant decreases Shc tyrosine phosphorylation and Shc-Grb2 association. This results in the inhibition of IGF-I-mediated ERK tyrosine phosphorylation and neurite outgrowth. In contrast, IGF-I induces a transient tyrosine phosphorylation of IRS-2 and an association of IRS-2 with Grb2. The time course of IRS-2 tyrosine phosphorylation and IRS-2-Grb2 and IRS-2-p85 association closely resembles the time course of IGF-I-mediated membrane ruffling. Treating cells with the phosphatidylinositol 3'-kinase inhibitors wortmannin and LY294002 blocks IGF-I-induced membrane ruffling. The ERK kinase inhibitor PD98059, as well as transfection with the p52 Shc mutant, has no effect on IGF-I-mediated membrane ruffling. Immunolocalization studies show IRS-2 and Grb2, but not Shc, concentrated at the tip of the extending growth cone where membrane ruffling is most active. Collectively, these results suggest that the association of Shc with Grb2 is essential for IGF-I-mediated neurite outgrowth, whereas the IRS-2-Grb2-phosphatidylinositol 3'-kinase complex may regulate growth cone extension and membrane ruffling.

Late embryonic lethality and impaired V(D)J recombination in mice lacking DNA ligase IV

The DNA-end-joining reactions used for repair of double-strand breaks in DNA and for V(D)J recombination, the process by which immunoglobulin and T-cell antigen-receptor genes are assembled from multiple gene segments, use common factors. These factors include components of DNA-dependent protein kinase (DNA-PK), namely DNA-PKcs and the Ku heterodimer, Ku70-Ku80, and XRCC4. The precise function of XRCC4 is unknown, but it interacts with DNA ligase IV. Ligase IV is one of the three known mammalian DNA ligases; however, the in vivo functions of these ligases have not been determined unequivocally. Here we show that inactivation of the ligase IV gene in mice leads to late embryonic lethality. Lymphopoiesis in these mice is blocked and V(D)J joining does not occur. Ligase IV-deficient embryonic fibroblasts also show marked sensitivity to ionizing radiation, growth defects and premature senescence. All of these phenotypic characteristics, except embryonic lethality, resemble those associated with Ku70 and Ku80 deficiencies, indicating that they may result from an impaired end-joining process that involves both Ku subunits and ligase IV. However, Ku-deficient mice are viable, so ligase IV must also be required for processes and/or in cell types in which Ku is dispensable.

Bidirectional regulation of p38 kinase and c-Jun N-terminal protein kinase by insulin-like growth factor-I

We have previously shown that insulin-like growth factor I (IGF-I) activation of the IGF-I receptor rescues SH-SY5Y human neuroblastoma cells from high glucose-mediated programmed cell death (PCD). In the current study, we further explored the potential points in the cell death cascade where IGF-I receptor activation may afford neuroprotection. As an initial step, we examined the effects of the PCD stimulus, high glucose, on stress-activated protein kinases, specifically the two mitogen-activated protein kinases p38 kinase and c-Jun N-terminal kinase (JNK). High glucose treatment activated the tyrosine phosphorylation of both p38 kinase and JNK in a dose- and time-dependent fashion. We next examined the effects of IGF-I on JNK and p38 kinase under normoglycemic and hyperglycemic conditions. IGF-I activated p38 kinase alone and had additive effects on glucose-induced p38 kinase phosphorylation. In contrast, IGF-I inhibited glucose activation of JNK phosphorylation and JNK activity. IGF-I also inhibited the glucose-induced nuclear translocation of JNK, but did not effect glucose-induced translocation of p38 kinase. Finally, IGF-I inhibition of JNK phosphorylation was blocked by the mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor, PD98059. Collectively, these data imply cross-talk between the mitogen-activated protein kinase pathway and JNK and suggest that IGF-I activation of mitogen-activated protein kinases interferes with JNK activation and protects cells from PCD.

[The comparative study of the quality of life for outpatient care versus community rehabilitation program schizophrenic patients]

The purpose of this study was to investigate the effects of demographic variables, illness factors and symptom factors on the quality of life in schizophrenic patients. Data were collected by personal interview and self-report questionnaire druing the month from February to March in 1995. A total of 155 schizophrenic patients purposefully selected from a psychiatric teaching hospital in Kaohsiung participated in the study. The data were analyzed by descriptive and inferential statistics. The quality of life was assessed in terms the following five parameters: activity, family support, psychological well-being, physical well-being, and economic function. In addition, the work status, subjective deficits symptoms and type of treatment program were uses as predictors of the total quality of life. These parameters shared 38% of their variance in stepwise multiple regression analysis. The findings indicated that schizophrenic patients who had participated in a rehabilitation program could maintain a well quality of life than in outpatient care only.

Growth retardation and leaky SCID phenotype of Ku70-deficient mice

Ku70, Ku80, and DNA-PKcs are subunits of the DNA-dependent protein kinase (DNA-PK), an enzyme implicated in DNA double-stranded break repair and V(D)J recombination. Our Ku70-deficient mice were about 50% the size of control littermates, and their fibroblasts were ionizing radiation sensitive and displayed premature senescence associated with the accumulation of nondividing cells. Ku70-deficient mice lacked mature B cells or serum immunoglobulin but, unexpectedly, reproducibly developed small populations of thymic and peripheral alpha/beta T lineage cells and had a significant incidence of thymic lymphomas. In association with B and T cell developmental defects, Ku70-deficient cells were severely impaired for joining of V(D)J coding and recombination signal sequences. These unanticipated features of the Ku70-deficient phenotype with respect to lymphocyte development and V(D)J recombination may reflect differential functions of the three DNA-PK components.

Molecular genetic characterization of XRCC4 function

XRCC4 is a generally expressed protein of 334 amino acids that is involved in the repair of DNA double-strand breaks and in V(D)J recombination, but its function is unknown. In this study, we have used a mutational approach and the yeast two-hybrid method to perform an initial characterization of this protein. We show that the XRCC4 protein is located in the nucleus. We also demonstrate that several potential phosphorylation sites are not required for XRCC4 function in a transient V(D)J recombination assay. In addition, we show that XRCC4 forms a homodimer in vivo with the homodimerization domain being located within amino acids 115-204. Finally, we define a core domain of XRCC4 that functions in V(D)J recombination and comprises amino acids 18-204. Potential functions of XRCC4 are discussed.

Prognostic significance of proliferating cell nuclear antigen expression in transitional cell carcinoma of the upper urinary tract

BACKGROUND

Haphazard cell proliferation is a fundamental biologic defect in cancer. Thus, assessment of the growth fraction provides a valuable index of biological property for human neoplasm. Proliferating cell nuclear antigen (PCNA) expression has been used to estimate the growth fraction of human cancer, and its prognostic value. Information in transitional cell carcinoma (TCC) of the upper urinary tract, however, is very few.

MATERIALS AND METHODS

A total of 73 patients with TCC of the upper urinary tract was collected between July 1988 and December 1995 for this study. The labeling index of PCNA immunostaining was correlated with clinicopathologic factors and compared for its prognostic value with a median follow-up of 54 months.

RESULTS

The PCNA index was positively associated with histological grading, tumor stage and patient prognosis (P = 0.00, respectively). Multivariate analysis demonstrated that significant factors in relation to patient survival were tumor stage (P = 0.01), followed by PCNA index (P = 0.04) and gender of patients (P = 0.04). Multiple comparison revealed that PCNA index set at 0.30 had prognostic value in terms of patient survival (P = 0.00), and the risk of metachronous bladder recurrence (P = 0.02).

CONCLUSION

Our data suggested that assessment of PCNA index may be used as an adjuvant prognostic factor for patients with TCC of the upper urinary tract.