Photofunctionalised Ti6Al4V implants enhance early phase osseointegration.

OBJECTIVES: Ultraviolet (UV) light-mediated photofunctionalisation is known to improve osseointegration of pure titanium (Ti). However, histological examination of titanium alloy (Ti6Al4V), which is frequently applied in orthopaedic and dental surgery, has not yet been performed. This study examined the osseointegration of photofunctionalised Ti6Al4V implants. METHODS: Ti and Ti6Al4V implants were treated with UV light, and the chemical composition and contact angle on the surfaces were evaluated to confirm photofunctionalisation. The implants were inserted into femurs in rats, and the rats were killed two or four weeks after the surgery. For histomorphometric analysis, both the bone-implant contact (BIC) ratio and the bone volume (BV) ratio were calculated from histological analysis and microcomputed tomography data. RESULTS: The amount of carbon and the contact angle on both implants were significantly reduced after UV irradiation. The BIC ratios for both UV light-treated implants significantly increased at two weeks, but there was no significant difference at four weeks. There was no significant difference in the BV ratios between the UV light-treated and control implants at two or four weeks. CONCLUSIONS: This study suggests that photofunctionalisation of Ti6Al4V implants, similar to that of Ti implants, may promotes osseointegration in early but not in the late phase of osseointegration.Cite this article: R. Yamauchi, T. Itabashi, K. Wada, T. Tanaka, G. Kumagai, Y. Ishibashi. Photofunctionalised Ti6Al4V implants enhance early phase osseointegration. Bone Joint Res 2017;6:331-336. DOI: 10.1302/2046-3758.65.BJR-2016-0221.R1.

Bactericidal and antimicrobial effects of pure titanium and titanium alloy treated with short-term, low-energy UV irradiation.

OBJECTIVES: The surface of pure titanium (Ti) shows decreased histocompatibility over time; this phenomenon is known as biological ageing. UV irradiation enables the reversal of biological ageing through photofunctionalisation, a physicochemical alteration of the titanium surface. Ti implants are sterilised by UV irradiation in dental surgery. However, orthopaedic biomaterials are usually composed of the alloy Ti6Al4V, for which the antibacterial effects of UV irradiation are unconfirmed. Here we evaluated the bactericidal and antimicrobial effects of treating Ti and Ti6Al4V with UV irradiation of a lower and briefer dose than previously reported, for applications in implant surgery. MATERIALS AND METHODS: Ti and Ti6Al4V disks were prepared. To evaluate the bactericidal effect of UV irradiation, Staphylococcus aureus 834 suspension was seeded onto the disks, which were then exposed to UV light for 15 minutes at a dose of 9 J/cm2. To evaluate the antimicrobial activity of UV irradiation, bacterial suspensions were seeded onto the disks 0, 0.5, one, six, 24 and 48 hours, and three and seven days after UV irradiation as described above. In both experiments, the bacteria were then harvested, cultured, and the number of colonies were counted. RESULTS: No colonies were observed when UV irradiation was performed after the bacteria were added to the disks. When the bacteria were seeded after UV irradiation, the amount of surviving bacteria on the Ti and Ti6Al4V disks decreased at 0 hours and then gradually increased. However, the antimicrobial activity was maintained for seven days after UV irradiation. CONCLUSION: Antimicrobial activity was induced for seven days after UV irradiation on both types of disk. Irradiated Ti6Al4V and Ti had similar antimicrobial properties.Cite this article: T. Itabashi, K. Narita, A. Ono, K. Wada, T. Tanaka, G. Kumagai, R. Yamauchi, A. Nakane, Y. Ishibashi. Bactericidal and antimicrobial effects of pure titanium and titanium alloy treated with short-term, low-energy UV irradiation. Bone Joint Res 2017;6:108-112. DOI: 10.1302/2046-3758.62.2000619.

Bazedoxifene blocks AGEs-RAGE-induced superoxide generation and MCP-1 level in endothelial cells.

Advanced glycation endproducts (AGEs) and their receptor (RAGE) play a role in vascular complications in diabetes. We have previously shown that 17ß-estradiol at 10 nmol/l, a nearly identical plasma concentration to that during mid-pregnancy, up-regulates RAGE expression in endothelial cells. The finding might suggest the involvement of 17ß-estradiol in the deterioration of vascular complications in diabetes during pregnancy. However, the effects of the selective estrogen receptor modulator, bazedoxifene, on oxidative and inflammatory reactions in AGEs-exposed endothelial cells remain unknown. In this study, we addressed the issue. Ten nmol/l 17ß-estradiol increased RAGE and monocyte chemoattractant protein-1 (MCP-1) gene and protein expression in human umbilical vein endothelial cells (HUVECs), both of which were blocked by 10 nmol/l bazedoxifene. Bazedoxifene at 10 nmol/l also significantly inhibited the AGEs-induced superoxide generation, RAGE and MCP-1 gene and protein expression in HUVECs. The present study suggests that blockade of the AGEs-RAGE axis by bazedoxifene might be a novel therapeutic target for preventing vascular damage in diabetes, especially in postmenopausal women.

Metformin inhibits advanced glycation end products (AGEs)-induced growth and VEGF expression in MCF-7 breast cancer cells by suppressing AGEs receptor expression via AMP-activated protein kinase.

Metformin use has been reported to decrease breast cancer incidence and mortality in diabetic patients. We have previously shown that advanced glycation end products (AGEs) and their receptor (RAGE) interaction stimulate growth and/or migration of pancreatic cancer and melanoma cells. However, effects of metformin on AGEs-RAGE axis in breast cancers remain unknown. We examined here whether and how metformin could block the AGEs-induced growth and vascular endothelial growth factor (VEGF) expression in MCF-7 breast cancer cells. Cell proliferation was measured with an electron coupling reagent WST-1 based colorimetric assay. Gene expression level was evaluated by real-time reverse-transcription polymerase chain reactions. AGEs significantly increased cell proliferation of MCF-7 cells, which was completely prevented by the treatment with 0.01 or 0.1 mM metformin or anti-RAGE antibodies. Furthermore, metformin at 0.01 mM completely suppressed the AGEs-induced upregulation of RAGE and VEGF mRNA levels in MCF-7 cells. An inhibitor of AMP-activated protein kinase, compound C significantly blocked the growth-inhibitory and RAGE and VEGF suppressing effects of metformin in AGEs-exposed MCF-7 cells. Our present study suggests that metformin could inhibit the AGEs-induced growth and VEGF expression in MCF-7 breast cancer cells by suppressing RAGE gene expression via AMP-activated protein kinase pathway. Metformin may protect against breast cancer expansion in diabetic patients by blocking the AGEs-RAGE axis.

Time-dependent gene expression and immunohistochemical analysis of the injured anterior cruciate ligament.

OBJECTIVES: This study aimed to investigate time-dependent gene expression of injured human anterior cruciate ligament (ACL), and to evaluate the histological changes of the ACL remnant in terms of cellular characterisation. METHODS: Injured human ACL tissues were harvested from 105 patients undergoing primary ACL reconstruction and divided into four phases based on the period from injury to surgery. Phase I was < three weeks, phase II was three to eight weeks, phase III was eight to 20 weeks, and phase IV was ≥ 21 weeks. Gene expressions of these tissues were analysed in each phase by quantitative real-time polymerase chain reaction using selected markers (collagen types 1 and 3, biglycan, decorin, α-smooth muscle actin, IL-6, TGF-ß1, MMP-1, MMP-2 and TIMP-1). Immunohistochemical staining was also performed using primary antibodies against CD68, CD55, Stat3 and phosphorylated-Stat3 (P-Stat3). RESULTS: Expression of IL-6 was mainly seen in phases I, II and III, collagen type 1 in phase II, MMP-1, 2 in phase III, and decorin, TGF-ß1 and α-smooth muscle actin in phase IV. Histologically, degradation and scar formation were seen in the ACL remnant after phase III. The numbers of CD55 and P-Stat3 positive cells were elevated from phase II to phase III. CONCLUSIONS: Elevated cell numbers including P-Stat3 positive cells were not related to collagens but to MMPs' expressions.

Rosuvastatin blocks advanced glycation end products-elicited reduction of macrophage cholesterol efflux by suppressing NADPH oxidase activity via inhibition of geranylgeranylation of Rac-1.

Adenosine triphosphate-binding membrane cassette transporter A1 (ABCA1) and ABCG1 play a crucial role in macrophage cholesterol efflux, which is a novel therapeutic target for atherosclerosis. Advanced glycation end products (AGE) and their receptor RAGE axis is involved in accelerated atherosclerosis in diabetes as well. However, the role of AGE-RAGE axis in macrophage cholesterol efflux is not fully understood. We examined here whether AGE-RAGE axis could impair cholesterol efflux from human macrophage cells, THP-1 cells by suppressing ABCA1 and ABCG1 expression. We further investigated the effects of rosuvastatin on cholesterol efflux from AGE-exposed THP-1 cells. AGE increased reactive oxygen species generation in THP-1 cells, which was completely inhibited by rosuvastatin, anti-RAGE-antibody or diphenylene iodonium chloride (DPI), an inhibitor of NADPH oxidase. The antioxidative effect of rosuvastatin on AGE-exposed THP-1 cells was significantly prevented by geranylgeranyl pyrophosphate (GGPP). AGE decreased ABCA1 and ABCG1 mRNA levels, and subsequently reduced cholesterol efflux from THP-1 cells, which was prevented by GGPP. DPI mimicked the effects of rosuvastain. The results demonstrated that rosuvastatin could inhibit the AGE-induced reduction of THP-1 macrophage cholesterol efflux by suppressing NADPH oxidase activity via inhibition of geranylgeranylation of Rac-1. Our present study provides a novel beneficial aspect of rosuvastatin in diabetes; rosuvastain may prevent the development and progression of atherosclerosis in diabetes by not only reducing serum cholesterol level, but also by improving cholesterol efflux from foam cells of the arterial wall via blocking the harmful effects of AGE on macrophages.

Involvement of retinoic acid-inducible gene-I in inflammation of rheumatoid fibroblast-like synoviocytes.

Interferon (IFN)-gamma is a major cytokine that regulates T helper 1-type immune reactions and serves as an important mediator in the pathogenesis of autoimmune diseases. Retinoic acid-inducible gene-I (RIG-I) is an IFN-gamma-inducible gene and known to be involved in the inflammatory and immune reactions. In the present study, we found high levels of RIG-I expression in synovial tissues of rheumatoid arthritis (RA), while the expression in osteoarthritis tissues was low. Treatment of cultured fibroblast-like synoviocytes with IFN-gamma markedly induced the expression of RIG-I. Knockdown of RIG-I in fibroblast-like synoviocytes, with specific siRNA, resulted in the inhibition of the IFN-gamma-induced expression of chemokine (C-X-C motif) ligand 10 (CXCL10)/IFN-gamma-inducible protein-10 (IP-10), a chemokine with chemotactic activity towards T cells. These findings suggest that RIG-I may play an important role in the pathogenesis of synovial inflammation in RA, at least in part, by regulating the IFN-gamma-induced expression of CXCL10/IP-10.

[Is delayed surgical repair admitted for the thrombosed aortic dissection?].

The initial treatment for the thrombosed aortic dissection is still controversial. Accordingly, we sought to evaluate the strategy of its surgical repair. Ninety-six (35 type A and 61 type B) acute thrombosed aortic dissection were studied retrospectively. Initially all of them were treated medically. The ratio of the false and the true lumen (F/T ratio) was calculated on the onset. The uncontrollable cardiac tamponade, recanalization, large ulcer-like projection (ULP) and enlargement of the dissected aorta had a delayed surgical repair during the follow-up period. Eighteen of the type A and 14 of the type B were surgically treated and showed good result. The 1- and 5-year survival rates and the event-free survival rates for the type A and the type B were almost equal with no statistical difference. The mean F/T ratio for the type A was 31% for the operative and 51% of the nonoperative cases (p = 0.007). The maximum size of the initial aorta of the operative cases was larger than that in the nonoperative for the type B. The conservative therapy for the thrombosed aortic dissection decreased the number of the unnecessary operation and the strategy of the delayed surgical repair was justified properly.

Prediction of recurrence after laparoscopic fundoplication for erosive reflux esophagitis based on anatomy-function-pathology (AFP) classification.

BACKGROUND: The usefulness of the anatomy-function-pathology (AFP) score was examined to evaluate its prediction of recurrence after laparoscopic fundoplication for erosive reflux esophagitis. METHODS: Of the patients undergoing laparoscopic fundoplication for erosive reflux esophagitis of Los Angeles classification grade A or higher from December 1994 to December 2004, 107 who underwent preoperative barium esophagogram, pH monitoring, and endoscopy were selected as subjects. The AFP score was calculated by A, F, and P factor grades of the AFP classification. By comparing patients with and without recurrence, the usefulness of the AFP score for predicting recurrence was examined. RESULTS: Reflux esophagitis recurred in seven patients. No significant difference in age, sex, or A or F factor was observed between the groups, whereas a significant difference was observed in the P factor (p = 0.008). On the other hand, the mean AFP score in the recurrence group was 16.9 +/- 5.3, whereas that in the nonrecurrence group was 8.9 +/- 5.3 (p = 0.0021). Among the patients with a score of 17 points or more (n = 23), recurrence was found in 6 patients (26%). On the other hand, among the patients with a score lower than 17 points (n = 84), recurrence was found in 1 patient, but not in the remaining 83 patients (1%). Sensitivity was thus 85.7% (95% confidence interval [CI], 42.1-99.6), and specificity was 83% (95% CI, 74.2-89.8). The positive predictive value was 26.1% (95% CI, 10.2-48.4), and the negative predictive value was 98.8% (95% CI, 93.5-99.9). Multiple logistic regression analysis was performed, and receiver operating characteristics curves were obtained. The area under the curve for the AFP score was 0.8457, whereas that for the P factor was 0.7907 (p = 0.0045), suggesting that the AFP score may more accurately predict recurrence than the P factor. CONCLUSION: The AFP score may be useful for predicting postoperative recurrence. If surgery is performed when the AFP score is lower than 17 points, the likelihood of postoperative recurrence is expected to be very low.

Analysis of the relationship between sex and chromosomal aberrations in colorectal cancer by comparative genomic hybridization.

Colorectal cancer is thought to be more common in men than in women. The chromosomal locations of DNA gains and losses in surgical specimens of colorectal tumours were detected by comparative genomic hybridization and were compared by gender. Five chromosomal regions, 7p, 8p, 8q, Xp and Xq, contained multiple gains that were significantly more common in males than in females, and within these regions, the differences were significant for Xp21, Xp11.3, Xp11.4 and Xq26. Regions 1p, 3q, 11q, 12p, 12q and 15q contained multiple sites of gain that were significantly more common in females than in males. Tumours from male and female patients showed significantly more losses at 11p and 15q, and at 4q and Xq, respectively. The fact that gains in X-chromosomal regions were detected with a significantly higher frequency in tumours from male patients suggests that the difference between the genders might be explained by X-chromosomal inactivation.

Laparoscopic Heller myotomy and Dor fundoplication for the treatment of achalasia. Assessment in relation to morphologic type.

BACKGROUND: The significance of laparoscopic Heller myotomy and Dor fundoplication (LHD) for the treatment of achalasia in relation to the severity of the lesion has not been sufficiently assessed. METHODS: Of patients who were diagnosed with achalasia from August 1994 to February 2004, 55 individuals who underwent LHD served as subjects. The therapeutic effects of LHD were assessed in terms of operation time, intraoperative complications, postoperative hospital stay, and symptom improvement in relation to morphologic type (spindle type, Sp; flask type, Fk; and sigmoid type, Sig). Degree of symptomatic improvement was classified into four grades: excellent, good, fair, and poor. RESULTS: Breakdown of morphologic type was as follows: Sp, n = 29; Fk, n = 18; and Sig, n = 8. Excluding one patient for whom conversion to open surgery was required, median average operation time for 54 patients was 160 min. As to intraoperative complications, esophageal mucosal perforation was seen in nine of the 55 patients (16%); however, conversion to open surgery could be avoided by suturing the affected area. Moreover, intraoperative bleeding of at least 100 g was seen in five of the 55 patients (9%), with one Fk patient requiring conversion to open surgery and transfusion. Median postoperative hospital stay was 8 days. Degree of dysphagia relief was excellent in 45 patients (83%), good in eight patients (15%), and fair in one patient (2%). Excellent improvement was obtained in 90%, 88%, and 50% in Sp, Fk, and Sig patients, respectively. Reflux esophagitis was seen in two patients, and was treated with a proton pump inhibitor. CONCLUSIONS: The results of the present study suggest that classification of morphologic type is a useful parameter in predicting postoperative outcome in achalasia. In order to achieve excellent symptomatic relief, surgery for achalasia should be recommended for but not limited to Sp and Fk types.

Hand-assisted laparoscopic and thoracoscopic surgery (HALTS) in radical esophagectomy with three-field lymphadenectomy for thoracic esophageal cancer.

AIM: To prove the feasibility of hand-assisted laparoscopic and thoracoscopic surgery (HALTS) for radical esophagectomy with three-field lymphadenectomy to thoracic esophageal cancer. METHODS: Esophagectomy with three-field lymphadenectomy was performed using HALTS in 19 patients with thoracic esophageal cancer without distant metastasis. Five patients had chemo-radiotherapy prior to surgery. RESULTS: All operations were completed successfully without the need for open surgery. Mean surgical time was 476+/-58 min, and mean blood loss during surgery was 343+/-184 mL. All patients started tube feeding and were moved from the intensive care unit to the general surgery ward the day after surgery. Discharge occurred a median of 10 days after surgery. Fifteen patients could return to full time jobs from 8 to 62 days after surgery (median 22 days) and from 1 to 35 days after discharge (median 9 days). Other three could return to daily activities at home soon as well. No major complications occurred, except one anastomotic leak. In terms of lung function, %FEV(1) was not changed whereas %VC was reduced significantly 1 month after surgery. All but two recurrences have been healthy without a relapse for a mean of 289 days. CONCLUSIONS: These results suggest that HALTS may be a useful surgical technique to reduce the invasiveness of conventional radical esophagectomy with three-field lymphadenectomy for thoracic esophageal cancer.

[Surgical management of papillary muscle rupture following acute myocardial infarction].

Papillary muscle rupture is a rare but severe complication of acute myocardial infarction. Two cases successfully underwent mitral valve replacement and concomitant coronary artery bypass grafting (CABG) for acute myocardial infarction with the anterior papillary muscle rupture in cardiogenic shock. Each of them needed preoperative massive inotropic infusion, respiratory support and intraaortic balloon pumping assist. The first case was a 76-year-old female. Double vessel disease (seg 7 : 90%, seg 11 : 100%) was revealed by coronary angiography and rupture of the papillary muscle was confirmed by transesophageal echocardiography. The second case was a 69-year-old female. Double vessel disease (seg 2 : 90%, seg 11 : 100%) was revealed and severe mitral regurgitation due to prolapse of the anterior leaflet was confirmed by transthoracic echocardiography. To assess the diagnosis of postinfarction papillary muscle rupture, transthoracic and/or transesophageal echocardiography is mandatory. Coronary angiography is also desirable because concomitant myocardial revascularization may improve the prognosis.

Endothelin protein expression as a significant prognostic factor in oesophageal squamous cell carcinoma.

The aim of this study was to investigate if the expression of endothelin (ET), a vasoactive peptide, in cancerous oesophageal lesions, adjacent dysplastic tissue and normal mucosa might be prognostic. Tissue samples from a total of 101 patients with oesophageal squamous cell carcinoma were obtained and stained with ET antibody in an immunohistochemical analysis. High staining levels of ET within normal mucosa were related to lymph vessel invasion, regional lymph node metastasis and distant metastasis, as well as a reduced relapse-free survival (log-rank test; P=0.0066). After adjustment for several histological prognostic risk factors and each component of the TNM classification system, high ET expression within dysplastic tissue more than doubled the hazard ratio of relapse with significant model improvement. These results suggest that, in addition to known histological risk factors and TNM classification criteria, measurement of ET expression with a simple immunohistochemical analysis might further help in predicting the prognosis of patients with oesophageal squamous cell carcinoma.

[Early and long-term outcome for surgical treatment of aortic arch aneurysm].

This study was undertaken to determine the factors that influence the final outcome after the operation of aortic arch aneurysm. Sixty-six patients, the median age was 72 years (range 44 to 90), were operated at our hospital during the 16-year period between 1985 and 2001. Preoperative complications included cardiac in 6 and vascular in 21, ruptured in 13, myocardial ischemia in 21 and stroke in 14. The distal hemiarch (11) and total arch replacement with or without ascending aorta and descending aorta (46) and proximal hemiarch with or without valve operations (7) and other procedures were performed mainly using cardio-pulmonary bypass with moderate deep hypothermia and selective cerebral perfusion. The in-hospital mortality were 6 (9%) and 14 (23%) late deaths occurred. One out of 14 was aneurysm related death. The survival rates were 81% at 1 year and 59% at 5 years. The multivariably determined risk factors for early death and postoperative neurological dysfunction were as follows (p < 0.05) cardiac anoxic arrest time, intubation time and gender.

Purification and identification of monoubiquitin-phosphoglycerate mutase B complex from human colorectal cancer tissues.

Ubiquitin-conjugated proteins in human colorectal cancer tissues were analyzed by the immunoprecipitation with the antibody FK2 against conjugated ubiquitin followed with SDS-PAGE. In these immunoprecipitable proteins, a 38-kDa protein was abundant in the tumor regions but almost absent in the adjacent normal regions in 17/26 patients, thus we attempted to purify it. Using immunoaffinity chromatography with the antibody FK2 followed by gel filtration and SDS-PAGE, approximately 10 pmol of this protein was separated from 34 g of the pooled cancerous tissue and transferred onto a PVDF membrane. The 38-kDa protein was further digested with Achromobacter protease I, resulting in several peptide fragments. Amino acid sequences of these peptides showed complete sequence identity to those derived from either ubiquitin or phosphoglycerate mutase-B, suggesting that the 38-kDa protein is monoubiquitinated phosphoglycerate mutase-B, whose calculated mass is 37,369 Da. Western blot using an antibody against phosphoglycerate mutase-B revealed the presence of the 38-kDa protein in the anti-ubiquitin immunoprecipitates derived from the tumor regions, but not from normal counterparts. In addition, part of non-ubiquitinated phosphoglycerate mutase-B (29 kDa) was also found in the anti-ubiquitin immunoprecipitates, whose levels were higher in the tumor regions than in the adjacent normal regions. These results suggest that monoubiquitination of phosphoglycerate mutase-B as well as formation of a noncovalent complex containing ubiquitin and phosphoglycerate mutase-B increases in colorectal cancer and novel modification of phosphoglycerate mutase-B might have a pathophysiological role.

[A case of pulmonary actinomycosis with recurrent hemoptysis diagnosed after right upper lobectomy].

The patient was a 58-year-old man who had been admitted in 1995 because of hemoptysis. Chest CT scans showed air-space consolidation with dilated bronchi and calcification in the right S3. He received a diagnosis of bronchiectasis with old tuberculosis. Bronchial arteriography showed arterialization in the right S3, and bronchial artery embolization was performed. But in 1996 hemoptysis reappeared. He was readmitted in May 1999 because of recurrent hemoptysis. Bronchial arteriography showed recurrence of arterialization in the same area, and chest CT scans showed growth of the mass shadow. Right upper lobectomy was performed, and the microscopic findings of the resected specimen showed sulfur granules in the dilated bronchus. We concluded that pulmonary actinomycosis should be considered in the differential diagnosis of abnormal chest shadows.

Fungal keratitis caused by Colletotrichum gloeosporioides.

PURPOSE: To describe a case of fungal keratitis caused by a rare coelomycete pathogen, Colletotrichum gloeosporioides. METHODS: An 82-year-old man with myelodysplastic syndrome developed fungal keratitis 6 months after cataract surgery in the left eye. Because the findings of the anterior chamber deteriorated after the initiation of natamycin, additional treatment with topical and systemic fluconazole was initiated. RESULTS: The isolates of corneal scraping grew C. gloeosporioides. After antifungal treatment of 2 months, the corneal lesion resolved with no recurrence of infection over a 5-year follow-up period. CONCLUSIONS: A combination treatment of natamycin and fluconazole was effective in the treatment of C. gloeosporioides.

Glutathione-S-transferase-pi expression regulates sensitivity to glutathione-doxorubicin conjugate.

We have reported that glutathione-doxorubicin conjugate (GSH-DXR) exhibited potent cytotoxicity against tumor cells and inhibited glutathione-S-transferase (GST) enzyme activity. In order to determine whether or not the expression of GST-pi lowered the cytotoxicity of GSH-DXR, cytocidal activity of the conjugate was examined using tumor cells in which the level of GST-pi expression was regulated by transfecting GST-pi cDNA in the correct or reverse direction and comparing with that of DXR. Enhancement of GST-pi expression by transfecting GST-pi sense cDNA into human hepatoblastoma HepG2 cells in which GST-pi expression was extremely low caused an increase in GST activity from 0.26 to 55.0 nmol/mg/min and a marked reduction in transfectant sensitivity to GSH-DXR to 1/120 (0.15-18 nM IC50) although the sensitivity to DXR was slightly decreased to 1/2.6 (380-990 nM IC50). By contrast, a high GST-pi-expressing human colon cancer cell line, HT29, showed a decrease in GST enzyme activity from 72.0 to 45.9 nmol/mg/min after transfecting GST-pi antisense cDNA and a marked improvement in transfectant sensitivity to GSH-DXR was observed (28-2.9 nM IC50) compared with the transfectant sensitivity to DXR (1020-320 nM IC50). Additionally, the expression of GST-pi in HepG2 cells caused a decrease in GSH-DXR-induced activation of caspase-3, which was an apoptotic marker, whereas the suppression of GST-pi in HT29 cells showed an increase in caspase-3 activation. These results suggested that the cytocidal efficacy of GSH-DXR, but not that of DXR, was controlled by the level of GST-pi expression in the cells.