Understanding effects of molecular adsorption at a single-wall boron nitride nanotube interface from density functional theory calculations

In this paper, we explored computationally the feasibility of modulating the bandgap in a single-wall BN nanotube (BNNT) upon noncovalent adsorption of organic molecules, combined with the application of a transverse electric field. Effects of analytes' physisorption on the surface of BNNTs regarding structural and electronic properties were delineated. Relatively large binding energies were calculated, however, with minimal perturbation of the structural framework. Electronic structure calculations indicated that the bandgap of BNNTs can be modified by weak adsorption due to the presence of adsorbate states in the gap of the host system. Furthermore, we have shown that the application of a transverse electric field can tune the bandgap by shifting adsorbate states, consistent with calculated current-voltage characteristics.

Intercellular adhesion molecule-1 K469E polymorphism in Korean patients with spontaneous preterm delivery

OBJECTIVES

To investigate the association between intercellular adhesion molecule-1 (ICAM-1) gene K469E polymorphism and spontaneous preterm delivery in a Korean population.

METHODS

Genomic DNA was extracted from whole blood from 55 women experiencing preterm labor and 153 multiparous women (control group) with a history of at least 2 term deliveries. DNA samples were analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The spontaneous preterm delivery (SPD) group carried the 469E allele significantly more frequently than those in the control group (odds ratio [OR], 1.62; 95% CI, 1.04-2.53). The EE genotype was significantly associated with increased risk of SPD (OR, 2.84; 95% CI, 1.17-6.89; P = 0.02). Allelic frequencies in women with abnormal C-reactive protein levels (K = 0.48; E = 0.52) were significantly different from frequencies in the controls (K = 0.68; E = 0.32) (P = 0.006).

CONCLUSIONS

ICAM-1 gene K469E polymorphism may be a candidate region and useful predictor of susceptibility to SPD in the Korean population.

Laparoscopy-assisted distal gastrectomy with D2 lymph node dissection for gastric cancer: technical and oncologic aspects

BACKGROUND

Laparoscopy-assisted distal gastrectomy (LADG) with lymph node dissection for advanced gastric cancer is still controversial. To evaluate the technical and oncologic feasibility and advantage of LADG with D2 lymph node dissection, the authors compared the surgical outcomes of LADG with D2 dissection and those of conventional open distal gastrectomy (ODG) for patients with early gastric cancer (EGC).

METHODS

Between September 2004 and August 2005, the study enrolled 75 patients with a preoperative diagnosis of EGC. Of these 75 patients, 44 underwent LADG, and remaining 31 underwent ODG. All the patients received D2 lymph node dissection. Their clinicopathologic characteristics, postoperative outcomes, and retrieved lymph nodes were compared at each station.

RESULTS

Although the operative time was significantly longer for the LADG group than for the ODG group, the perioperative recovery was shorter and, consequently, the postoperative hospital stay was significantly shorter for the LADG group (7.7 vs 9.4 days, respectively; p = 0.003). No significant differences were found in the total number of retrieved lymph nodes (37.2 vs 42.4; p > 0.05) or node stations (p > 0.05) between the two groups.

CONCLUSIONS

LADG with D2 lymph node dissection is a safe and feasible procedure, and it is oncologically compatible with open gastrectomy. A large-scaled prospective randomized trial with advanced gastric cancer patients should be conducted to confirm the benefit of LADG.

Treatment results for gastric cancer surgery: 12 years' experience at a single institute in Korea

AIMS

To evaluate the changing trends of clinicopathologic features, surgical procedures and treatment outcomes of gastric cancer in a large-volume center.

METHODS

We divided the time period into two parts: the first is 1989-1996 (period I) and the second is 1997-2001 (period II). Then we analyzed prospectively collected data on 1816 patients treated at Kangnam St. Mary's Hospital, The Catholic University of Korea, from 1989 to 2001.

RESULTS

Upper one-third cancer was seen more prevalently in period II than period I (9.4% versus 6.6%) (p=0.000) and total gastrectomy was performed more frequently in period II than period I (25% versus 18%) (p=0.000). A diagnosis of early gastric cancer was made more prevalently in period II than period I (40% versus 27%) (p=0.000). D2 lymphadenectomy was done in 74% of the period I patients and 83% of their period II counterparts (p=0.000). Between the two periods, there was a significant difference in the incidence of operation-related major complications (9.9% in period I versus 3.9% in period II) (p=0.000) and the mortality (1.8% versus 0.6%) (p=0.023). The overall 5-year and 10-year survival rates were significantly higher in period II than period I (63% and 57% in period I versus 69% and 64% in period II) (p=0.009).

CONCLUSIONS

The overall survival of gastric cancer significantly increased because of the early detection and aggressive surgical approaches by experienced surgeons in a large-volume center. More effective multidisciplinary approaches are warranted to improve the prognosis of advanced gastric cancer.

Thromboembolic complications in patients with clear cell carcinoma of the ovary

OBJECTIVE

The purpose of this study was to define the incidence of deep venous thrombosis (DVT) and pulmonary embolism (PE) in patients with clear cell carcinoma (CCC) of the ovary and to investigate the prognostic factors in such patients.

METHODS

Between January 1987 and December 2003, 641 women with primary invasive epithelial ovarian cancer underwent treatment at the Royal Hospital for Women in Sydney, Australia. Sixty-six patients (10.3%) with CCC were identified from the data bank, and their data were compared with a matched-control group of 132 patients with non-clear cell epithelial ovarian carcinoma.

RESULTS

A thromboembolic event (DVT or PE) was noted in 27.3% of patients with CCC, compared to 6.8% of patients with other epithelial ovarian cancers. PE was detected in 13.6% and 3.8% of patients, respectively. In patients with CCC, DVT was frequently observed before operation or at the time of recurrence. In a multivariate analysis of patients matched for age and stage, the occurrence of a DVT or the presence of endometriosis was significant predictors of clear cell histology. Within the clear cell group, no particular risk factor for DVT could be identified. Metastases of 50 mm or greater in diameter, ascites of 1000 ml or more, advanced FIGO stage, and the occurrence of DVT were poor prognostic factors for CCC in univariate analysis, but in a multivariate Cox regression analysis, only FIGO stage and occurrence of DVT remained significant.

CONCLUSION

The incidence of venous thromboembolic events was found to be significantly higher in patients with CCC when compared to patients with other epithelial ovarian cancers.

Abdominal Aortic Aneurysm Repair in Kidney Transplant Recipients

Renal transplant recipients currently survive many years with a consequent increase in the risk of presentation with vascular diseases. So aortic reconstruction in transplant patients has been increasingly reported the most common procedures involving abdominal aorta aneurysms (AAAs). The most important problem during the operation is ischemic injury to the transplanted kidney during aortic clamping. Protection for the grafted kidney from ischemic or reperfusion injury may be achieved by permanent or temporary axillo-femoral, femoro-femoral, aorto-iliac bypass, cold perfusion, local cold preservation, or autotransplantation. Some authors have reported protection of the transplanted kidney function without any other procedures. We had experience with four AAA cases in kidney transplant patients, including two cases of direct reconstruction of the AAA without any other surgical protection, one autotransplantation, and one AAA excision with using temporary aortofemoral bypass with good results. Herein, we report two cases of successful AAA excision without a surgical procedure for graft protection.

Resonance Raman spectroscopy characterization of single-wall carbon nanotube separation by their metallicity and diameter

Several techniques were recently reported for the bulk separation of metallic (M) and semiconducting (S) single wall carbon nanotubes (SWNTs), using optical absorption and resonance Raman spectroscopy (RRS) as a proof of the separation. In the present work, we develop a method for the quantitative evaluation of the M to S separation ratio, and also for the SWNT diameter selectivity of the separation process, based on RRS. The relative changes in the integrated intensities of the radial-breathing mode (RBM) features, with respect to the starting material, yield the diameter probability distribution functions for M and S SWNTs in the separated fractions, accounting for the different resonance conditions of individual SWNTs, while the diameter distribution of the starting material is obtained following the fitting procedure developed by Kuzmany and coworkers. Features other than the RBM are generally less effective for characterization of the separation process for SWNTs.

Patterns of treatment failure following radiotherapy with combination chemotherapy for patients with high-risk stage IIB cervical carcinoma

BACKGROUND

To evaluate the patterns of treatment failure in patients with stage IIB cervical carcinoma with high-risk factors following radiotherapy given concurrently with combination chemotherapy.

METHODS

A retrospective analysis of 349 patients with stage IIB cervical carcinoma with high-risk factors (lesion size >/= 4 cm, lymph node metastasis, high-risk cell type) treated by radiotherapy and cisplatin-based chemotherapy was performed. Sites of treatment failure were categorized as pelvic, pelvic plus distant metastases, and distant metastases alone. Pelvic failure included local and pelvic nodal failures.

RESULTS

Of the 349 patients, treatment failure occurred in 79 patients (22.6%). Forty-six (13.2%) had persistent disease and 33 (9.5%) had recurrent disease. Among these 79 patients, overall pelvic failure was observed in 67%, of whom 72% had local failure; 19%, pelvic nodal failure; and 9%, local with pelvic nodal failure. Incidences of distant metastases alone and pelvic with distant metastases were 24% and 9%. In the 26 patients with distant metastases either alone or combined with pelvic failure, the most frequent metastatic region was the paraaortic lymph node (50%). The distant metastasis rate was 6.5% (19/289) in the pelvic tumor control group and 11.6% (7/60) in the pelvic failure group. Pelvic failure was the most frequent failure in the group with tumor size of 4 cm or more, whereas, for the positive-lymph-node group, distant metastasis was most frequent and metastases to paraaortic lymph nodes were common. The incidences of pelvic failure alone and distant metastases were similar in the high-risk cell-type group, and the distant metastasis regions were mostly paraaortic lymph nodes.

CONCLUSION

Although systemic chemotherapy was administered concurrently with radiotherapy, the incidence of pelvic failure was highest, followed by paraaortic lymph node metastases, in patients with stage IIB cervical carcinoma with high-risk factors, following radiotherapy with combination chemotherapy. To evaluate the patterns of treatment failure in patients with stage IIB cervical carcinoma with high-risk factors following radiotherapy given concurrently with combination chemotherapy.

Postoperative adjuvant therapy in early invasive cervical cancer patients with histopathologic high-risk factors

The purpose of this study is to evaluate the efficacy of postoperative adjuvant therapy in preventing treatment failure after primary treatment with surgery in early invasive cervical cancer patients associated with the following histopathologic high-risk factors: lymph node metastasis (either macroscopic or microscopic), parametrial extension, lymphovascular permeation and depth of invasion > or =10 mm. Postoperative adjuvant concurrent chemoradiotherapy (PCCRT), postoperative adjuvant chemotherapy (PCT), or postoperative adjuvant radiotherapy (PRT) alone was administered to the 80 early invasive cervical cancers with at least one of the high-risk factors. Each of 61 patients received three to six cycles of chemotherapy at intervals of approximately 3 weeks. Twenty three patients were treated with PCCRT, 38 patients were treated with PCT alone, and 19 patients received PRT. The 5-year survival rates of patients with macroscopic lymph node metastasis were 66.7% and 35.7% in PCCRT and PRT, respectively. With microscopic lymph node metastasis, the 5-year survival rates were 83.3%, 60.0%, and 70.1% in PCCRT, PCT, and PRT, respectively. With parametrial extension, the 5-year survival rate was 58.1% in PCCRT. The 5-year survival rates of patients with lymphovascular permeation were 100%, 90.9%, and 66.7% in PCCRT, PCT, and PRT, respectively. With depth of invasion > or =10 mm, the 5-year survival rates were 100% and 91.3%, in PCCRT and PCT, respectively. PCCRT appears to be superior to PRT or PCT alone in early invasive cervical cancer patients with histopathologic high-risk factors.

8-Cl-cAMP induces cell cycle-specific apoptosis in human cancer cells

8-Cl-cyclic adenosine monophosphate (8-Cl-cAMP) has been known to induce growth inhibition and differentiation in a variety of cancer cells by differential modulation of protein kinase A isozymes. To understand the anticancer activity of 8-Cl-cAMP further, we investigated the effect of 8-Cl-cAMP on apoptosis in human cancer cells. Most of the tested human cancer cells exhibited apoptosis upon treatment with 8-Cl-cAMP, albeit with different sensitivity. Among them, SH-SY5Y neuroblastoma cells and HL60 leukemic cells showed the most extensive apoptosis. The effect of 8-Cl-cAMP was not reproduced by other cAMP analogues or cAMP-elevating agents, showing that the effect of 8-Cl-cAMP was not caused by simple activation of protein kinase A (PKA). However, competition experiments showed that the binding of 8-Cl-cAMP to the cAMP receptor was essential for the induction of apoptosis. After the treatment of 8-Cl-cAMP, cells initially accumulated at the S and G2/M phases of the cell cycle and then apoptosis began to occur among the population of cells at the S/G2/M cell cycle phases, indicating that the 8-Cl-cAMP-induced apoptosis is closely related to cell cycle control. In support of this assumption, 8-Cl-cAMP-induced apoptosis was blocked by concomitant treatment with mimosine, which blocks the cell cycle at early S phase. Interestingly, 8-Cl-cAMP did not induce apoptosis in primary cultured normal cells and non-transformed cell lines, showing that 8-Cl-cAMP-induced apoptosis is specific to transformed cells. Taken together, our results show that the induction of apoptosis is one of the mechanisms through which 8-Cl-cAMP exerts anticancer activity.

Molecular cloning and characterization of groESL operon in Streptococcus pneumoniae

GroEL is a major target of the immune defense in infection and seems to be negatively regulated by HrcA in gram-positive organisms. However, HrcA's mechanism has not been elucidated. To elucidate the role of groEL in Streptococcus pneumoniae, the groESL operon was cloned in Escherichia coli. The promoter region of the pneumococcal groESL operon contained a sigmaA type promoter and an inverted repeat (CIRCE). A Northern blot analysis of the groESL operon demonstrated that the groESL operon is transcribed as a bicistronic mRNA, and reached maximum expression 7.5 to 10 min after heat shock. A primer extension analysis showed a potential transcription start point at 155 bp upstream of the translation start site, preceding the groES gene. The putative negative regulator of the groEL gene, hrcA, of S. pneumoniae was recovered by PCR-based chromosomal walking from grpE locus. A sequence analysis showed a sigmaA type promoter flanked by 2 CIRCE elements. His-tagged HrcA was overexpressed as a soluble form in E. coli and bound to the CIRCE regions in the promoter of both groESL and dnaK operons in vitro. Additionally, a helix-loop helix motif, a putative DNA binding domain, was found at the C-terminal of HrcA. These results will help to determine the nature of HrcA in the groESL repression.

Dicaffeoyl- or digalloyl pyrrolidine and furan derivatives as HIV integrase inhibitors

Human immunodeficiency virus (HIV) integrase (IN) catalyzes the integration of HIV DNA copy into the host cell DNA. Such integration is essential for the production of progeny viruses, and therefore therapeutic agents that can inhibit this process should be effective anti-HIV agents. We have previously reported the inhibitory activity of dicaffeoylglucosides against HIV IN. In the present study, we have synthesized and tested dicaffeoyl or digalloyl compounds joined through a five-membered heterocyclic ring as HIV IN inhibitors to explore the SARs of this family of compounds. The starting heterocyclic diols were prepared from L-tartaric acid, diethyl L-tartarate or D-(+)-ribonic gamma-lactone. We found that the HIV IN inhibitory activities of dicaffeoyl derivatives were comparable to that of L-chicoric acid (IC(50)=24.9 microM). On the other hand, digalloyl derivatives were more potent than L-chicoric acid with IC(50) values of 4.7--15.6 microM.

Caspase-mediated Cdk2 activation is a critical step to execute transforming growth factor-beta1-induced apoptosis in human gastric cancer cells

Although TGF-beta1, a growth inhibitor, is known to also induce apoptosis, the molecular mechanism of this apoptosis is largely undefined. Here, we identify the mechanism of TGF-beta1-induced apoptosis in SNU-16 human gastric cancer cells. Cell cycle and TUNEL analysis showed that, upon TGF-beta1 treatment, cells were initially arrested at the G1 phase and then driven into apoptosis. Of note, caspase-3 was activated in accordance with TGF-beta1-induced G1 arrest. Activated caspase-3 is targeted to cleave p21(cip1), p27(kip1), and Rb, which play important roles in TGF-beta-induced G1 arrest, into inactive fragments. Subsequently, Cdk2 was aberrantly activated due to the cleavage of p21 and p27. We found that the inhibition of Cdk2 activity efficiently blocks TGF-beta1-induced apoptosis, whereas it did not prevent caspase-3 activation or the subsequent cleavage of target proteins. In contrast, the suppression of caspase-3 activity inhibited the cleavage of target proteins, the activation of Cdk2, and the induction of apoptosis. Taken together, our results suggest that activation of caspase-3 by TGF-beta1 may initiate the conversion from G1 cell cycle arrest to apoptosis via the cleavage of p21, p27 and Rb, which in turn causes Cdk2 activation and, most significantly, Cdk2 activation as a downstream effector of caspase is a critical step for the execution of TGF-beta1-induced apoptosis.

Disseminated superficial actinic porokeratosis with both typical and prurigo nodularis-like lesions

We report a 50-year-old Korean patient who developed a disseminated superficial actinic porokeratosis (DSAP) with two types of lesions. One was a typical DSAP lesion clinically and histopathologically. The other was clinically similar to prurigo nodularis, but histologic examination showed the findings of porokeratosis such as cornoid lamellae and loss of the granular layer in addition to those of chronic lichenified dermatitis, so it could be described as prurigo nodularis-like porokeratosis. The nodular lesions seemed to develop on preexisting typical lesions of DSAP mainly during the summer by the aggravation of pruritic symptoms and scratching associated with sun exposure. Although we could not find any published reports describing lesions like those of our case, we think that such prurigo nodularis-like porokeratosis can develop in patients with DSAP in some situations involving pruritus and scratching.

Antiepiligrin cicatricial pemphigoid with autoantibodies to the beta subunit of laminin 5 and associated with severe laryngeal involvement necessitating tracheostomy

We report the case of a 67-year-old Korean woman with antiepiligrin cicatricial pemphigoid. The patient's serum immunoprecipitated polypeptides that comigrated with those identified in serum from a representative patient with antiepiligrin cicatricial pemphigoid, and was reactive with the laminin beta3-subunit on immunoblotting. She presented not only with cutaneous, oral and ocular, but also with laryngeal and esophageal involvement. Because the supraglottic stenosis was severe, she had to undergo tracheostomy to maintain airway patency.

6-Hydroxy-1,3-dioxin-4-ones as non-peptidic HIV protease inhibitors

HIV protease inhibitors containing 6-hydroxy-1,3-dioxin-4-one ring system as a new scaffold have been prepared. Among them, compound 4d showed potent HIV protease inhibitory activity (IC50 = 0.01 microM) and antiviral activity in cell culture (EC50 = 0.96 microM, SI = 65.69).

Synthesis and HIV-1 integrase inhibitory activities of caffeoylglucosides

Caffeoylglucosides, which have a glucose ring as a central linker, were synthesized from methyl D-glucosides, and their anti-HIV-1 activities were tested. Among them, four dicaffeoylglucosides (IC50 = 29.1+/-35.1 microM), 6a, 6b, 9b and 10b, showed HIV-1 integrase inhibitory activity as potent as L-chicoric acid.

Concurrent chemotherapy and radiotherapy in invasive cervical cancer patients with high risk factors

The aim of this study was to evaluate the survival of 395 previously untreated cervical cancer patients with at least one high risk factor following concurrent chemoradiation and to assess the toxicities. Two different chemotherapy regimens were used for concurrent chemoradiation. In the patients with squamous cell carcinoma, 100 mg/m2 of cisplatin was infused intravenously, followed immediately by five consecutive daily administrations of 5-fluorouracil, 1,000 mg/m2/day, each infused intravenously over 24 hr. As for the patients with adenocarcinoma, 70 mg/m2 of cisplatin, 250 mg/m2 of cytoxan and 45 mg/m2 of adriamycin were administered intravenously on days 1, 2, and 3, respectively. The 5-year survival rate was 54.4% with stage III and IV, 62.6% with lymph node metastasis on computed tomogram or MRI, 77.9% with stage I-II disease with lesion size > or =4 cm, and 50.3% with small cell carcinoma or adenocarcinoma. Side effects from concurrent chemoradiation such as nausea, vomiting, and alopecia were present in all 395 cases. Anemia, leukopenia, thrombocytopenia, hepatotoxicity, and nephrotoxicity were observed to varying degrees, but there was no toxic death. This study suggests that cisplatin-based concurrent chemoradiation in treating cervical cancer patients with high risk factors is effective and relatively well tolerated, with acceptable toxicity.

Dual anticancer activity of 8-Cl-cAMP: inhibition of cell proliferation and induction of apoptotic cell death

8-Cl-cAMP induces apoptotic cell death in human cancer cells. To look at this more closely, we examined the changes in the levels of Bcl-2 family proteins during 8-Cl-cAMP-induced apoptosis of SH-SY5Y human neuroblastoma cells. Following the treatment with 8-Cl-cAMP, Bcl-2 was transiently down-regulated and Bad was increased continuously up to day 5. In addition, overexpression of Bcl-2 efficiently blocked the 8-Cl-cAMP-induced apoptosis, suggesting Bcl-2 family proteins may be involved in the 8-Cl-cAMP-induced apoptosis. The contribution of the apoptotic cell death and the inhibition of cell proliferation in the 8-Cl-cAMP-induced growth inhibition was closely monitored in the Bcl-2-overexpressing cells. Though the apoptosis was reduced significantly, no significant difference was observed in the inhibition of cell proliferation up to day 2 of 8-Cl-cAMP treatment. These results suggest that 8-Cl-cAMP exerts anticancer activity by two distinct mechanisms, i.e. , through the inhibition of cell proliferation as well as the induction of apoptosis. Supporting this notion was the observations that (1) suppression of apoptosis by zVAD did not abrogate 8-Cl-cAMP-induced inhibition of cell proliferation, and (2) 8-Cl-cAMP did not show additive inhibition of cell proliferation in RIIbeta-overexpressing cells.

High incidence of multidrug-resistant Streptococcus pneumoniae in South Korea

Streptococcus pneumoniae was isolated from patients with bacteremia, meningitis, pneumonia, and otitis media and used to determine susceptibility to various antibiotics. Of 105 isolates, 51% to 83% were resistant to 6 antibiotics (i.e., the percentages of resistance to penicillin, ampicillin, cephalothin, chloramphenicol, tetracycline, and erythromycin were 78%, 67%, 51%, 56%, 83%, and 58%, respectively). Also, 66 of the 105 isolates were multidrug resistant. Seventy-eight percent of multidrug-resistant strains were highly resistant to tetracycline (minimum inhibitory concentration [MIC] > or = 50 micrograms/ml), and 39% of multidrug-resistant strains were also highly resistant to erythromycin (MIC > or = 128 micrograms/ml). However, only 4% of the 105 isolates were resistant to cefotaxime.

Participation of type II protein kinase A in the retinoic acid-induced growth inhibition of SH-SY5Y human neuroblastoma cells

To examine the role of protein kinase A (EC 2.7.1.37) isozymes in the retinoic acid-induced growth inhibition and neuronal differentiation, we investigated the changes of protein kinase A isozyme patterns in retinoic acid-treated SH-SY5Y human neuroblastoma cells. Retinoic acid induced growth inhibition and neuronal differentiation of SH-SY5Y cells in a dose- and time-dependent manner. Neuronal differentiation was evidenced by extensive neurite outgrowth, decrease of N-Myc oncoprotein, and increase of GAP-43 mRNA. Type II protein kinase A activity increased by 1.5-fold in differentiated SH-SY5Y cells by retinoic acid treatment. The increase of type II protein kinase A was due to the increase of RIIbeta and Calpha subunits. Since type II protein kinase A and RIIbeta have been known to play important role(s) in the growth inhibition and differentiation of cancer cells, we further investigated the role of the increased type II protein kinase A by overexpressing RIIbeta in SH-SY5Y cells. The growth of RIIbeta-overexpressing cells was slower than that of parental cells, being comparable to that of retinoic acid-treated cells. Retinoic acid treatment further increased the RIIbeta level and further inhibited the growth of RIIbeta-overexpressing cells, showing strong correlation between the level of RIIbeta and growth inhibition. However, RIIbeta-overexpressing cells did not show any sign of neuronal differentiation and responded to retinoic acid in the same way as parental cells. These data suggest that protein kinase A participates in the retinoic acid-induced growth inhibition through the up-regulation of RIIbeta/type II protein kinase A.

Characterization of epidermal growth factor receptor function in lysophosphatidic acid signaling in PC12 cells

Lysophosphatidic acid (LPA) is a lipid metabolite that induces the activation of mitogen-activated protein kinase (MAPK) through binding to the G protein-coupled receptor in a number of cell lines and cultures. Recent studies have revealed that LPA is able to rapidly induce the phosphorylation of MAPK through an epidermal growth factor (EGF) receptor-dependent pathway. We investigated the role of the EGF receptor in the signaling pathway initiated by LPA stimulation in nerve growth factor (NGF)-responsive PC12 cells well known to transiently retract their own neurites upon LPA stimulation. LPA-stimulated MAPK signaling was suppressed by the selective EGF receptor inhibitor and in the dominant negative mutant EGF receptor cell line. As in the EGF signaling pathway, the complex of EGF receptor with adapter proteins Shc and Sos was formed in response to LPA stimulation, suggesting there is an intracellular mechanism for transactivation. A neurite retraction assay was also performed to examine the role of the EGF receptor in PC12 cell differentiation, which related to the involvement of LPA-induced neurite retraction. These results suggest that the receptor tyrosine kinase can be activated in a ligand-independent manner through intracellular crosstalk between the signaling pathways.