Association Between FOXP3/CD8 Lymphocyte Ratios and Tumor Infiltrating Lymphocyte Levels in Different Breast Cancer Subtypes.

BACKGROUND/AIM: Patients with non-luminal breast cancer subtypes with high levels of tumor infiltrating lymphocytes (TILs) have better prognosis than those with luminal subtype. We evaluated the role of TILs according to the subtype. MATERIALS AND METHODS: An immunohistochemical analysis of 139 breast cancer cases was conducted to calculate the FOXP3+/CD8+ T cell ratios and their relationships with TILs and disease-free survival (DFS) were evaluated. RESULTS: FOXP3+/CD8+ T cell ratios were significantly associated with TIL levels only in luminal breast cancers (p=0.0001). Low FOXP3+/CD8+ T cell ratio was significantly associated with longer DFS (p=0.017). All luminal subtype patients with high TIL levels had high FOXP3+/CD8+ T cell ratios compared to only half of non-luminal subtype patients with high TIL levels. CONCLUSION: High FOXP3+/CD8+ T cell ratios in breast cancers may partly explain the worse prognosis of luminal breast cancers, but not that of non-luminal breast cancers with high TIL levels.

Significant association between high serum CCL5 levels and better disease-free survival of patients with early breast cancer.

Analysis of anticancer immunity aids in assessing the prognosis of patients with breast cancer. From 250 operated breast cancers, we focused on serum levels of C-C motif chemokine ligand 5 (CCL5), which is involved in cancer immune reactions. Serum levels of CCL5 were measured using a cytometric bead-based immunoassay kit and CCL5 expression in cancer cells was determined using immunohistochemical staining. In addition, mRNA in cancer and stromal cells was analyzed by microdissection and comparison with the public dataset. Disease-free survival (DFS) of patients with high CCL5 levels (cut-off, 13.87 ng/mL; n = 192) was significantly better than those with low CCL5 levels (n = 58; hazard ratio, 0.20; 95% confidence interval, 0.10-0.39; P < .0001). An improved overall survival was observed in patients with high CCL5 levels compared to those with low CCL5 levels (P = .024). On the contrary, high immunohistochemical expression of CCL5 in cancer cells was significantly associated with decreased DFS. As serum CCL5 levels did not correlate with CCL5 expression in cancer cells and the relative expression of mRNA CCL5 was elevated in stromal cells in relation to cancer cells, serum CCL5 might be derived not from cancer cells, but from stromal cells. Expression of CCL5 in serum, but not in cancer cells, might contribute to improved patient prognosis mediating through not only immune reaction, but through other mechanisms. Determination of circulating CCL5 levels could be useful for predicting patient prognosis.

High Serum Levels of Interleukin-18 Are Associated With Worse Outcomes in Patients With Breast Cancer.

BACKGROUND/AIM: Interleukin (IL)-18, which belongs to the IL-1 superfamily of cytokines, is a known interferon-gamma (IFN-γ)-inducing factor. Since IFN-γ plays an essential role in anticancer immunity mediated through cytotoxic T cells, IL-18 may also contribute to the function of immunosurveillance. The aim of the study was to examine the association of IL-18 with the outcomes of patients with breast cancer. PATIENTS AND METHODS: Serum IL-18 levels were determined at baseline in 270 patients operated for breast cancer, and the relapse-free survival (RFS) was compared between IL-18-high and -low groups. The relationships between IL-18 and tumor-infiltrating lymphocytes (TILs) or the neutrophil-to-lymphocyte ratio (NLR) were also investigated. RESULTS: The RFS of patients was significantly better in the IL-18-low group than in the IL-18-high group (p=0.032). According to the multivariate analysis, IL-18 was a significant and independent predictive factor for RFS (hazard ratio(HR)=0.336; 95% confidence interval(CI)=0.147-0.727; p=0.0053). No association was observed between the IL-18 levels and TILs or NLRs. CONCLUSION: IL-18 levels may be useful for predicting the prognosis of patients who have received surgical treatment for breast cancer.

Fbxo22-mediated KDM4B degradation determines selective estrogen receptor modulator activity in breast cancer.

The agonistic/antagonistic biocharacter of selective estrogen receptor modulators (SERMs) can have therapeutic advantages, particularly in the case of premenopausal breast cancers. Although the contradictory effects of these modulators have been studied in terms of crosstalk between the estrogen receptor α (ER) and coactivator dynamics and growth factor signaling, the molecular basis of these mechanisms is still obscure. We identify a series of regulatory mechanisms controlling cofactor dynamics on ER and SERM function, whose activities require F-box protein 22 (Fbxo22). Skp1, Cullin1, F-box-containing complex (SCFFbxo22) ubiquitylated lysine demethylase 4B (KDM4B) complexed with tamoxifen-bound (TAM-bound) ER, whose degradation released steroid receptor coactivator (SRC) from ER. Depletion of Fbxo22 resulted in ER-dependent transcriptional activation via transactivation function 1 (AF1) function, even in the presence of SERMs. In living cells, TAM released SRC and KDM4B from ER in a Fbxo22-dependent manner. SRC release by TAM required Fbxo22 on almost all ER-SRC-bound enhancers and promoters. TAM failed to prevent the growth of Fbxo22-depleted, ER-positive breast cancers both in vitro and in vivo. Clinically, a low level of Fbxo22 in tumor tissues predicted a poorer outcome in ER-positive/human epidermal growth factor receptor type 2-negative (HER2-negative) breast cancers with high hazard ratios, independently of other markers such as Ki-67 and node status. We propose that the level of Fbxo22 in tumor tissues defines a new subclass of ER-positive breast cancers for which SCFFbxo22-mediated KDM4B degradation in patients can be a therapeutic target for the next generation of SERMs.

Abundant tumor infiltrating lymphocytes after primary systemic chemotherapy predicts poor prognosis in estrogen receptor-positive/HER2-negative breast cancers.

PURPOSE: The therapeutic effect of systemic treatment for breast cancer (BC) generally depends on its intrinsic subtypes. In addition, tumor infiltrating lymphocytes (TILs) are considered to be an independent factor for tumor shrinkage and disease prognosis. High TILs at baseline or after primary systemic chemotherapy are reported to be associated with better survival in triple-negative or human epithelial growth factor receptor 2 (HER2)-positive BCs. However, the prognostic value of TILs in estrogen receptor (ER)-positive and HER2-negative (ER+/HER2-) BC is still controversial. METHODS: We assessed TIL score (low, intermediate, and high) before and after primary systemic chemotherapy in every subtype of BC, and compared the clinical outcomes. Biopsy specimens of 47 triple-negative, 58 HER2+ and 91 ER+/HER2- BCs were used to assess TILs before treatment. To assess TILs after treatment, we examined residual invasive carcinoma in surgically resected samples of 28 triple-negative, 30 HER2+ and 80 ER+/HER2- BCs. RESULTS: A high TIL score in triple-negative BC before treatment resulted in a significantly higher proportion of pathological complete response (pCR). In contrast, ER+/HER2- BC exhibited fewer instances of pCR than other subtypes. Although not statistically significant, ER+/HER2- cases with a high TIL score also tended to achieve pCR (p = 0.088). Moreover, we revealed that low TIL BCs after chemotherapy, but not at baseline, had significantly better relapse-free survival in ER+/HER2- BC (p = 0.034). CONCLUSION: Pathological examination of TILs after treatment may be a surrogate marker for prognosis in ER+/HER2- BC.

Tumor size and proliferative marker geminin rather than Ki67 expression levels significantly associated with maximum uptake of 18F-deoxyglucose levels on positron emission tomography for breast cancers.

It has been well established that maximum standardized uptake value (SUVmax) for 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (FDG PET/CT) is clinically useful for evaluating treatment efficacy as well as predicting prognosis of breast cancer patients. Although SUVmax reflects increased glucose uptake and metabolism possibly induced by activation of growth factor signaling or TP53 dysfunction, tumor characteristics of SUVmax-high breast cancers remain to be elucidated. For the present study, we used immunohistochemical staining to investigate expressions of phospho-ribosomal protein S6 (pS6, downstream molecule of phosphatidyl inositol 3-kinase/Akt/mammalian target of the rapamycin/S6K pathway) and phosphor-p44/42 mitogen-activated protein kinase (pMAPK). Expression levels of TP53 and proliferative marker geminin as well as Ki67 were also examined by means of immunostaining in 163 invasive breast cancers. Cutoff values were set at 10% for pS6, 20% for pMAPK and TP53, and 4% for geminin. The SUVmax levels were significantly higher in the pS6-positive (p = 0.0173), TP53-positive (p = 0.0207) and geminin-high cancers (p<0.0001), but there was no significant association between pMAPK expression levels and SUVmax levels. Multivariable analysis showed that a high geminin level (odds ratio: 6.497, 95% confidence interval: 2.427-19.202, p = 0.0001) and large tumor size (6.438, 2.224-20.946, p = 0.0005) were significantly and independently associated with SUVmax-high. Univariable but not multivariable analysis indicated that Ki67-high significantly correlated with SUVmax-high. Twenty of 23 (87.0%) breast cancers with tumor size >2cm and geminin-high showed SUVmax-high, while only 6 of 49 (12.2%) breast cancers ≤2cm in size and with low geminin levels were SUVmax-high. In conclusion, we could determine that breast cancers with a large tumor and a geminin-high rather than Ki67-high proliferative marker were significantly associated with high levels of SUVmax. These findings may signify that SUVmax reflects tumor characteristics with high proliferative activity but not activation of mTOR/S6K and MAPK pathways or increased glucose metabolism due to dysfunction of TP53.

Prognostic significance of geminin expression levels in Ki67-high subset of estrogen receptor-positive and HER2-negative breast cancers.

BACKGROUND: Indication for chemotherapy in estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancers is determined on the basis of Ki67 expression level. However, since Ki67-high cancers are not necessarily sensitive to chemotherapy, identification of such patients who do not need chemotherapy is an important issue. PATIENTS AND METHODS: We used immunohistochemical staining to examine the expression levels of ER, progesterone receptor (PgR), Ki67, and geminin, a marker of S to G2/M phases, in 80 ER-positive/HER2-negative breast cancers. The labeling indices of Ki67 and geminin were determined and cutoff values were set at 15 and 6 %, respectively. RESULTS: Ki67 and geminin expression levels were significantly associated with nuclear grade. In the Ki67-low subset, 26 out of 28 (92.9 %) cancers were geminin low and in the Ki67-high subset, 31 out of 52 (59.6 %) were geminin high. Distant disease-free survival (DDFS) of the geminin-high subset was significantly poorer than that of the geminin-low subset (P = 0.009). In the Ki67-low subset, only one patient showed recurrence. Metastasis was detected in eight out of 31 (25.8 %) patients in the geminin-high group of the Ki67-high subset, but no recurrence was observed in the geminin-low group of the Ki67-high subset. CONCLUSION: Geminin-high breast cancers are significantly associated with worse prognosis. Since poorer prognosis was recognized only in the geminin-high group in Ki67-high cancers, we speculate that geminin may be useful for identifying patients in the Ki67-high subset who can avoid unnecessary chemotherapy.

Activation of mTOR/S6K But Not MAPK Pathways Might Be Associated With High Ki-67, ER(+), and HER2(-) Breast Cancer.

UNLABELLED: We determined the activation of the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways in 108 cases of estrogen receptor-positive and human epidermal growth factor receptor 2-negative breast cancer with high and low Ki-67 expression. The expression levels of Ki-67, p53, phosphorylated MAPK (pMAPK), and protein S6 (pS6; downstream molecule of PI3K/Akt/mammalian target of rapamycin/S6 kinase pathway) were determined immunohistochemically. pS6 positivity, but not pMAPK positivity, was significantly associated with the high Ki-67 expression subset. BACKGROUND: Evaluation of luminal A and luminal B characteristics of estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer is considered important. Although the phosphoinositide 3 kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways are thought to be involved in the luminal B subtype, the details of their contribution to breast cancer remain unclear. MATERIALS AND METHODS: We determined the activation of these pathways (phosphorylated MAPK [pMAPK] and protein S6 [pS6; a downstream molecule of PI3K/Akt/mammalian target of rapamycin (mTOR)/S6 kinase (S6K)]) in 108 ER(+), HER2(-) breast cancer cases with high and low Ki-67 expression. The ER, progesterone receptor (PgR), Ki-67, p53 expression levels were also determined immunohistochemically. The cutoff value for Ki-67 was set at 15%. RESULTS: A significantly greater percentage of cancer cases with high Ki-67 expression showed pS6 positivity than did those with low Ki-67 expression (53.2% vs. 19.7%; P = .0003). No significant differences were found between the cases with high and low expression levels were detected for p53 (23.4% vs. 11.5%; P = .12) or pMAPK (36.2% vs. 34.4%; P = .85) positivity. Multivariate analysis showed that pS6 positivity (odds ratio 5.16, 95% confidence interval 1.95-13.63; P = .0009), nuclear grade 2 and 3, and low PgR expression (≤ 20%) were independently associated with the high Ki-67 subset. CONCLUSION: From our findings, we have concluded that the pS6 expression level is associated with the characteristics of breast cancer with high Ki-67 expression. Because these associations were observed, irrespective of menopausal status, the biologic difference seems to be less affected by estrogen signaling than by activation of S6 protein, especially in terms of proliferation. Our findings have also indicated that targeting the mTOR/S6K pathway might be a useful strategy for the treatment of ER(+)/HER2(-) breast cancer with high Ki-67 expression.

C4.4A highly expressed in HER2-positive human breast cancers may indicate a good prognosis.

BACKGROUND: The aim of our study was to investigate the association of C4.4A expression in breast tumors with both patients' clinicopathological characteristics and outcomes in order to clarify the significance of C4.4A in breast cancer. METHODS: Primary breast cancer patients (n = 125, stage I-III) who had undergone breast mastectomy or breast-conserving surgery at our hospital between 2005 and 2011 were recruited for this study. Tumor samples were obtained from surgical specimens and expression status of C4.4A, estrogen receptors, progesterone receptors, human epidermal growth factor receptor 2 (HER2) and Ki67 was analyzed immunohistochemically, while HER2 amplification was examined using fluorescence in situ hybridization. RESULTS: Multivariate analysis showed that HER2 positivity was the only independent predictive factor for C4.4A expression (odds ratio 5.31, 95 % confidence interval 2.04-15.72; P < 0.001). Univariate prognostic analysis of the relationship between C4.4A and disease-free survival showed that survival of patients with C4.4A-positive tumors was longer than that of patients with C4.4A-negative tumors in the HER2-positive subset (P = 0.004) while there was no significant difference in patient outcome according to C4.4A status for total patients (median observation period 37 months, range 1-92 months; P = 0.223). CONCLUSIONS: We established a positive relationship between C4.4A and HER2 status, suggesting that C4.4A expression may be a prognostic factor for HER2-positive breast cancer patients.

Biological characteristics of luminal subtypes in pre- and postmenopausal estrogen receptor-positive and HER2-negative breast cancers.

BACKGROUND: Estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancers can be divided into luminal A and luminal B subtypes based on Ki67 expression levels. However, the biological differences in ER and progesterone receptor (PR) expression levels between these luminal subtypes are not clear. METHODS: We examined immunohistochemical expression levels of ER, PR, and Ki67 in 180 ER-positive/HER2-negative breast cancers while taking menopausal status into account. Breast cancers were divided according to ER and PR levels (H: >50%, L: ≤ 50%), and luminal A and B were classified by the Ki67 labeling index (A: Ki67 <14%, B: Ki67 ≥ 14%). RESULTS: When breast cancers were classified based on ER and PR levels, the distribution of pre- and postmenopausals was significantly different for luminal A (P < 0.0001), but not for luminal B cancers. As for luminal A, ER-H/PR-L cancers were rare among premenopausals (8%), but frequent among postmenopausals (54%). Correlation between ER and PR levels among luminal A cancers was strong in premenopausals but weak in postmenopausals. Since crosstalk with growth factor signaling is unlikely in luminal A, we speculate that intratumoral estrogen insufficiency contributed to the characteristics of postmenopausal ER-H/PR-L cancers. CONCLUSION: We speculate that the biological characteristics of luminal A cancers are influenced by the estrogen environment, but its influence on luminal B cancers may be limited. We believe these considerations constitute useful information for a better understanding of the biology of ER-positive-HER2-negetive breast cancers.

Coexistence of giant blue nevus of the scalp with hair loss and alopecia areata.

A 43-year-old Japanese man presented with a 13-year history of a grayish macule measuring 7 cm in diameter with sparse hairs on the vertex. Histopathological examination demonstrated two types of melanocytes, spindle-shaped and ovoid cells, with abundant melanin aggregated around the upper part of the pilosebaceous apparatus. Fibrous, thick collagen bundles were also seen surrounding the upper part of the small hair follicles. There was no infiltration of melanocytes or lymphocytes in the lower dermis or adipose tissue. Based on these findings, a diagnosis of blue nevus, cellular type, was made. Giant cellular blue nevi on the scalp are rare, and 11 cases reported in the published work have shown characteristic features such as hair loss and cranial invasion of nevus cells. It should be noted that melanocytes of giant blue nevi have a high potential to damage other organs such as underlying bone and hair follicles. The patient also showed a typical lesion of alopecia areata on the left temporal which was successfully treated with topical corticosteroid.

APEX1 Asp148Glu gene polymorphism is a risk factor for lung cancer in relation to smoking in Japanese.

DNA repair enzymes play an important role in the development of various kinds of cancer. We here analyzed associations of XPD Lys751Gln, APEX1 Asp148Glu, XRCC1 Arg399Gln, and XRCC3 Thr241Met gene polymorphisms in DNA repair pathways in relation to the risk of lung cancer using PCR-RFLP. The study involved 104 lung cancer patients and 120 non-cancer controls divided into non-smokers and smokers. We found a statistically significant interaction between APEX1 Asp148Glu and the risk for lung cancer (adjusted OR 2.78, 95% CI 1.58-4.90, p=0.0004), of both adenocarcinoma (adjusted OR 2.24, 95%CI 1.18-4.25, p=0.014) and squamous cell carcinoma (adjusted OR 4.75, 95%CI 1.79-12.6, p=0.002) types. XRCC1 Arg399Gln showed a borderline significant association with adenocarcinoma (adjusted OR 1.89, 95%CI 1.00-3.57, p=0.051). The combined effect of smoking and presence of the APEX1 Asp148Glu demonstrated a significant association with risk of lung cancer (adjusted OR 3.61, 95% CI 1.74-7.50, p=0.001). The XPD Lys751Gln and XRCC3 Thr241Met genotypes displayed no statistically significant risk. Our findings suggest that the APEX1 Asp148Glu is associated with increased risk for primary lung cancer in Japanese individuals partaking in smoking.

[A case of ruptured giant liver cyst complicated by Candida infection].

A 75-year-old woman who had been given a diagnosis of a giant liver cyst occupying the right hepatic lobe was admitted to our hospital complaining of abdominal pain. CT examination revealed the size of cyst was smaller than before and the level of CRP was elevated, suggesting the development of peritonitis due to rupture of the cyst. As Candida albicans was detected from both ascites and the cyst, we treated her with continuous percutaneous transhepatic drainage and antimycotic agents. The cyst markedly diminished, and she became free of infection and peritonitis, suggesting drainage was exceedingly effective.

MUTYH Gln324His gene polymorphism and genetic susceptibility for lung cancer in a Japanese population.

BACKGROUND: Genetic polymorphisms of DNA repair enzymes in the base excision repair (BER) pathway, may lead to genetic instability and lung cancer carcinogenesis. We investigated the interactions among the gene polymorphisms in DNA repair genes and lung cancer. METHODS: We analyzed associations among OGG1 Ser326Cys and MUTYH Gln324His gene polymorphisms in relation to lung cancer risk using PCR-RFLP. The study involved 108 lung cancer patients and 121 non-cancer controls divided into non-smokers, smokers according to pack-years smoked in Japanese. RESULTS: The results showed that the MUTYH His/His genotype compared with Gln/Gln genotype showed an increased risk for lung cancer (adjusted odds ratio [OR] 3.03, confidence interval [95%CI], 1.31-7.00, p = 0.010), whereas there was no significant increase for the Gln/His genotype (adjusted OR 1.35, 95%CI 0.70-2.61, p = 0.376). The MUTYH His/His genotype was at a borderline increased risk for both adenocarcinoma and squamous cell carcinoma (adjusted OR 2.50, 95%CI 0.95-6.62, p = 0.065 for adenocarcinoma; adjusted OR 3.20, 95%CI 0.89-11.49, p = 0.075 for squamous cell carcinoma, respectively). However, the OGG1 Ser/Cys or Cys/Cys genotypes compared with the Ser/Ser genotype did not have significantly increased risk for lung cancer, containing either adenocarcinoma or squamous cell carcinoma. The joint effect of tobacco exposure and the MUTYH His/His genotype compared with the Gln/Gln genotype showed a significant association with lung cancer risk in smokers, and there was not significantly increased in non-smokers (adjusted OR 3.82, 95%CI 1.22-12.00, p = 0.022 for smokers; adjusted OR 2.60, 95%CI 0.60-11.25, p = 0.200 for non-smokers, respectively). The effect of tobacco exposure and the OGG1 Ser326Cys showed also no significant risk for lung cancer. CONCLUSION: Our findings suggest that the MUTYH Gln324His polymorphism appear to play an important role in modifying the risk for lung cancer in the Japanese population.

Association of MUTYH Gln324His and APEX1 Asp148Glu with colorectal cancer and smoking in a Japanese population.

BACKGROUND: Genetic polymorphisms of DNA repair enzymes may lead to genetic instability and colorectal cancer carcinogenesis. Our objective was to measure the interactions between polymorphisms of repair genes and tobacco smoking in colorectal cancer. METHODS: The case-control study involved sixty-eight colorectal cancer patients and 121 non-cancer controls divided into non-smokers and smokers according to pack-years of smoking. The genetic polymorphisms of DNA repair enzymes,OGG1 Ser326Cys, MUTYH Gln324His, APEX1 Asp148Glu and XRCC1 Arg399Gln, were examined using PCR-RFLP. RESULTS: The MUTYH Gln324His showed strong significant associations with a risk of colorectal cancer (crude odds ratio [OR] 3.30, 95% confidence interval [95%CI] 1.44-7.60, p = 0.005; adjusted OR3.53, 95%CI 1.44-8.70, p = 0.006). The ORs for the APEX1 Asp148Glu were statistically significant (crude OR 2.69, 95%CI 1.45-4.99, p = 0.002; adjusted OR 2.33, 95%CI 1.21-4.48, p = 0.011). The ORs for the MUTYH Gln324His and the APEX1 Asp148Glu were statistically significant for colon cancer (adjusted OR 3.95, 95%CI 1.28-12.20, p = 0.017 for MUTYH Gln324His ; adjusted OR 3.04, 95%CI 1.38-6.71, p = 0.006 for APEX1 Asp148Glu). The joint effect of tobacco exposure and the MUTYH Gln324His showed a significant association with colorectal cancer risk in non-smokers (adjusted OR 4.08, 95%CI 1.22-13.58, p = 0.022) and the APEX1 Asp148Glu was significantly increased in smokers (adjusted OR 5.02, 95%CI 1.80-13.99, p = 0.002). However, the distributions of OGG1 Ser326Cys and XRCC1 Arg399Gln were not associated with a colorectal cancer risk. CONCLUSION: Our findings suggest that the MUTYH Gln324His and the APEX1 Asp148Glu constitutes an increased risk of colorectal cancer, especially colon cancer. The MUTYH Gln324His is strongly associated with colorectal cancer susceptibility in never smoking history, whereas the APEX1 Asp148Glu genotype constitutes an increased risk of colorectal cancer when accompanied by smoking exposure.

Involvement of multidrug resistance-associated protein 2 in intestinal secretion of grepafloxacin in rats.

We investigated the contribution of multidrug resistance-associated protein 2 (MRP2) to the secretory transport of grepafloxacin and compared its functional role with that of P-glycoprotein (P-gp) by using Sprague-Dawley rats (SDRs) and Eisai hyperbilirubinemic rats (EHBRs), in which MRP2 is hereditarily defective. In intestinal tissue from SDRs mounted in Ussing chambers, the level of transport in the direction from the serosal layer to the mucosal layer was twofold greater than that in the direction from the mucosal layer to the serosal layer. This secretory transport of grepafloxacin was diminished by both probenecid, an MRP2 inhibitor, and cyclosporine, a P-gp inhibitor. In intestinal tissue from EHBRs, the secretory transport of grepafloxacin was lower than that in intestinal tissue from SDRs and was inhibited by cyclosporine but not by probenecid. The absorption of grepafloxacin from intestinal loops in SDRs was in the order of duodenum > jejunum > ileum and was increased by cyclosporine but not by probenecid. The absorption in EHBRs was not higher than that in SDRs. The intestinal secretory clearance in SDRs after intravenous administration of grepafloxacin was shown to be greater for the ileum than for the duodenum, which is in good agreement with the previously reported regional expression profile of MRP2 mRNA. The intestinal secretory clearance was lower in EHBRs than in SDRs. Accordingly, in addition to P-gp, MRP2 might play a role in the secretory transport of grepafloxacin. The function of MRP2 in facilitating grepafloxacin transport in the secretory direction is more pronounced both in vitro and in vivo, while the restriction of entry from the lumen into the cell by MRP2 seems to be negligible, compared with that by P-gp, in the case of grepafloxacin.