Percutaneous ultrasound-guided cryoablation for early-stage primary breast cancer: a follow-up study in Japan.

BACKGROUND: Ultrasound-guided percutaneous cryoablation (PCA) for early-stage breast cancer (ESBC) can be performed under local anesthesia in an outpatient clinic. This study continues a pilot stage to examine local control, safety, patient quality of life (QoL), satisfaction and cosmetic outcomes of cryoablation for ESBC. METHODS: PCA was performed under local anesthesia for patients with primary ESBC, followed by radiation and endocrine therapies. Oncologic outcomes were examined by imaging (mammography, ultrasound, MRI) at baseline and 1, 6, 12, 24, 36, and 60 months post-cryoablation. EQ-VAS, EQ-5D-5L, subjective satisfaction and Moiré topography were used to measure health-related QoL outcomes. RESULTS: Eighteen patients, mean aged 59.0 ± 9.0 years, mean tumor size 9.8 ± 2.3 mm, ER + , PR + (17/18), HER2-, Ki67 < 20% (15/18), underwent PCA and were followed for a mean of 44.3 months. No serious adverse events were reported, and no patients had local recurrence or distant metastasis in the 5-year follow-up. Cosmetic outcomes, satisfaction level, and QoL all improved post-cryoablation. Five-year average reduction rates of the cryolesion long, short, and depth diameters, on US, were 61.3%, 42.3%, and 22.8%, respectively, compared to the 86.2% volume reduction rate on MRI. The correlation coefficient between MRI and US measurement criteria was highest for the long diameter. During follow-up, calcification of the treated area was observed in 13/18 cases. CONCLUSION: Cryoablation for ESBC is an effective and safe procedure with excellent cosmetic outcomes and improved QoL. This study contributes to the growing evidence supporting cryoablation as a potential standard treatment for ESBC, given compliance to pre-defined patient selection criteria.

Replication Study for the Association of Five SNPs Identified by GWAS and Trastuzumab-Induced Cardiotoxicity in Japanese and Singaporean Cohorts.

Trastuzumab (herceptin) is an effective drug for human epidermal growth factor receptor type 2 (HER2)-positive cancer. However, cardiotoxicity remains a serious complication. In our previous genome-wide association study (GWAS), we identified potential associations for five single nucleotide polymorphisms (SNPs) with trastuzumab-induced cardiotoxicity in a Japanese population. To validate this association, here we performed replication studies using Japanese and Singaporean case-control cohorts (Japan: 6 cases and 206 controls; Singapore: 22 cases and 178 controls). Although none of the SNPs showed a statistically significant association with trastuzumab-induced cardiotoxicity, we show that three (rs8032978, rs7406710 and rs9316695) and four (rs8032978, rs7406710, rs28415722 and rs11932853) SNPs had an effect in the same direction in the Japanese and the Singaporean cohort, respectively, as that in our previous study. Combining the previous study with the current replication studies, we find a strong association for two SNPs, rs8032978 and rs7406710, with trastuzumab-induced cardiotoxicity (Pcombined = 4.92 × 10-5 and 5.50 × 10-5, respectively). These data suggest that rs8032978 and rs7406710 could be predictive markers of trastuzumab-induced cardiotoxicity in Japanese and Singaporean populations, and support their potential use in clinical risk assessment. These findings offer a first step toward the development of clinically available markers for the potential risk of trastuzumab-induced cardiotoxicity as well as an improved understanding of the pathogenesis of this complication.

[Clinical Significance of the Curative Effect after Neoadjuvant Chemotherapy for Triple-Negative Breast Cancer-Correlation to Prognosis].

We investigated factors related to the recurrence and prognosis of patients with triple-negative breast cancer (TNBC)after neoadjuvant chemotherapy(NAC). Of the 545 patients who underwent surgery after NAC between January 2013 and December 2016, 131 patients had TNBC. An analysis of each TNBC case indicated that the presence or absence of clinical lymph node metastasis(cN)before treatment might be a predictive factor of prognosis. There were 57(43.5%)pathological complete response(pCR)(ypT0 or ypTis/N0)cases after NAC. Overall survival(OS)and disease free survival(DFS) were significantly better in pCR cases than in non-pCR cases. However, recurrence was observed in 8 of 57(14%)pCR cases and 29 of 74(39%)non-pCR cases. The factors defining DFS from the univariate analysis of the non-pCR group were cN, ypT, ypN, and vascular invasion. The multivariate analysis of these factors suggested that residual cN and vascular invasion might be independent factors predicting DFS. Residual vascular invasion was found to predict OS, and was considered to be a poor prognostic factor.

A Genome-Wide Association Study Identifies Five Novel Genetic Markers for Trastuzumab-Induced Cardiotoxicity in Japanese Population.

Trastuzumab has been administered to patients with human epidermal growth factor receptor 2 (HER2)-positive cancer, however, the cardiotoxicity is identified as one of the life-threatening toxicities. Clinically useful biomarker for trastuzumab-induced cardiotoxicity has been expected to be developed. To identify a novel genetic marker(s) determining the risk of trastuzumab-induced cardiotoxicity, we performed a first genome-wide association study (GWAS) in Japanese population. We enrolled 481 patients who had been treated with trastuzumab and carried out a GWAS using 11 cases (with cardiotoxicity) and 257 controls (without cardiotoxicity). Top 100 single nucleotide polymorphisms (SNPs) which revealed the smallest p values in GWAS (p = 7.60 × 10-7 - 2.01 × 10-4) were further examined using replication samples consisted of 14 cases and 199 controls. The combined analysis of the GWAS and replication study indicated possible association of five loci with trastuzumab-induced cardiotoxicity (rs9316695 on chromosome 13q14.3, rs28415722 on chromosome 15q26.3, rs7406710 on chromosome 17q25.3, rs11932853 on chromosome 4q25, and rs8032978 on chromosome 15q26.3, Pcombined = 6.00 × 10-6, 8.88 × 10-5, 1.07 × 10-4, 1.42 × 10-4, 1.60 × 10-4, respectively). Furthermore, we developed a risk prediction model for trastuzumab-induced cardiotoxicity using the five marker SNPs. The incidence of trastuzumab-induced cardiotoxicity in patients with risk score ≥5 was significantly higher (42.5%) compared to that in patients with score ≤ 4 (1.8%) (p = 7.82 × 10-15, odds ratio = 40.0). These findings suggest the potential to improve the ability of physicians to avoid the trastuzumab-induced cardiotoxicity for patients with HER2-positive cancer.

Trastuzumab Emtansine (T-DM1) Plus S-1 in Patients with Trastuzumab-Pretreated HER2-Positive Advanced or Metastatic Breast Cancer: A Phase Ib Study.

BACKGROUND: In treating human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer, the efficacy of capecitabine combined with HER2-directed agents such as trastuzumab and lapatinib is supported by some evidence. The combination of T-DM1 and S-1, another oral 5-FU, may be a safe alternative treatment for metastatic breast cancer. OBJECTIVES: The optimal dose of S-1 was evaluated in combination with T-DM1 for patients with HER2-positive advanced or metastatic breast cancer. The safety and clinical response of this combination treatment were also assessed. METHODS: This 3 + 3 dose-escalation study of S-1 given for the first 2 of 3 weeks, in combination with T-DM1 (3.6 mg/kg given every 3 weeks) to patients with trastuzumab-pretreated HER2-positive advanced or metastatic breast cancer was designed to evaluate the dose-limiting toxicity (DLT) occurrence in the first cycle. We also evaluated the safety and clinical activity of this combination treatment in multiple cycles. Two different dose levels of S-1 (65 and 80 mg/m2/day) were planned, although the capecitabine arm was abandoned because of slow recruitment. RESULTS: Twelve out of the 13 patients enrolled were evaluable for DLT. One DLT (grade ≥3 non-hematological adverse events) occurred at dose level 0, leading to the expansion of this cohort to 6 patients, with an additional DLT (≥7 days discontinuation of medication), while no DLT occurred at dose level 1. As a result, the maximum tolerable dose of S-1 was determined to be 80 mg/m2/day for 14 days with T-DM1 3.6 mg/kg, repeated every 3 weeks. Two patients had grade 3 thrombocytopenia at dose level 0, and 1 patient at dose level 1. CONCLUSIONS: S-1 can be safely combined with the clinically relevant dose of T-DM1 in patients with HER2-positive advanced or metastatic breast cancer. Further evaluation with a larger sample size is required for efficacy assessment.

A genome-wide association study identifies three novel genetic markers for response to tamoxifen: A prospective multicenter study.

PURPOSE: Although association studies of genetic variations with the clinical outcomes of breast cancer patients treated with tamoxifen have been reported, genetic factors which could determine individual response to tamoxifen are not fully clarified. We performed a genome-wide association study (GWAS) to identify novel genetic markers for response to tamoxifen. EXPERIMENTAL DESIGN: We prospectively collected 347 blood samples from patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative, invasive breast cancer receiving preoperative tamoxifen monotherapy for 14 to 28 days. We used Ki-67 response in breast cancer tissues after preoperative short-term tamoxifen therapy as a surrogate marker for response to tamoxifen. We performed GWAS and genotype imputation using 275 patients, and an independent set of 72 patients was used for replication study. RESULTS: The combined result of GWAS and the replication study, and subsequent imputation analysis indicated possible association of three loci with Ki-67 response after tamoxifen therapy (rs17198973 on chromosome 4q34.3, rs4577773 on 6q12, and rs7087428 on 10p13, Pcombined = 5.69 x 10-6, 1.64 x 10-5, and 9.77 x 10-6, respectively). When patients were classified into three groups by the scoring system based on the genotypes of the three SNPs, patients with higher scores showed significantly higher after/before ratio of Ki-67 compared to those with lower scores (P = 1.8 x 10-12), suggesting the cumulative effect of the three SNPs. CONCLUSION: We identified three novel loci, which could be associated with clinical response to tamoxifen. These findings provide new insights into personalized hormonal therapy for the patients with breast cancer.

Feasibility Study of Weekly Nanoparticle Albumin-Bound Paclitaxel (150 mg/m2) Followed by Fluorouracil, Epirubicin, and Cyclophosphamide Therapy as Neoadjuvant Chemotherapy for HER2-Negative Breast Cancer.

BACKGROUND: Although several studies have shown efficacy of nanoparticle albumin-bound (nab) paclitaxel use as a neoadjuvant treatment in breast cancer, dosage and schedules were varied or used in combination and the data are still limited for weekly regimens. We evaluated the feasibility of weekly nab-paclitaxel followed by FEC (5-FU [fluorouracil], epirubicin, and cyclophosphamide) treatment feasibility as neoadjuvant chemotherapy for breast cancer. PATIENTS AND METHODS: Thirty-three patients with no previous chemotherapy were enrolled to receive nab-paclitaxel 150 mg/m2 the first 3 of 4 weeks (3q4w) followed by FEC as neoadjuvant treatment. The trial was powered for analyses of feasibility. RESULTS: Twenty-five patients completed the treatment as per protocol, and the completion rate was 75.8% (95% confidence interval, 59.0-87.2; P = .44). The regimen completion group was younger than those with regimen incompletion (average 45.1 vs. 56.6 years). The pathological complete response (ypT0-is/N0) rate was 30.3% in 33 patients, which was higher in triple-negative patients (58.3%). Grade 3/4 neutropenia was seen in 48.5%, although there was no febrile neutropenia. Grade 3 peripheral neuropathy was seen in 33.3%. CONCLUSION: Our study showed that weekly nab-paclitaxel 150 mg/m2 3q4w followed by FEC as neoadjuvant regimen might be sufficient in efficacy, although with a relatively high severe adverse event occurrence rate.

Significant Effect of Polymorphisms in CYP2D6 on Response to Tamoxifen Therapy for Breast Cancer: A Prospective Multicenter Study.

Purpose: CYP2D6 is the key enzyme responsible for the generation of the potent active metabolite of tamoxifen, "endoxifen." There are still controversial reports questioning the association between CYP2D6 genotype and tamoxifen efficacy. Hence, we performed a prospective multicenter study to evaluate the clinical effect of CYP2D6 genotype on tamoxifen therapy.Experimental Design: We enrolled 279 patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative, invasive breast cancer receiving preoperative tamoxifen monotherapy for 14 to 28 days. Ki-67 response in breast cancer tissues after tamoxifen therapy was used as a surrogate marker for response to tamoxifen. We prospectively investigated the effects of allelic variants of CYP2D6 on Ki-67 response, pathological response, and hot flushes.Results: Ki-67 labeling index in breast cancer tissues significantly decreased after preoperative tamoxifen monotherapy (P = 0.0000000000000013). Moreover, proportion and Allred scores of estrogen receptor-positive cells in breast cancer tissues were significantly associated with Ki-67 response (P = 0.0076 and 0.0023, respectively). Although CYP2D6 variants were not associated with pathologic response nor hot flushes, they showed significant association with Ki-67 response after preoperative tamoxifen therapy (P = 0.018; between two groups, one with at least one wild-type allele and the other without a wild-type allele).Conclusions: This is the first prospective study evaluating the relationship between CYP2D6 variants and Ki-67 response after tamoxifen therapy. Our results suggest that genetic variation in CYP2D6 is a key predictor for the response to tamoxifen in patients with breast cancer. Clin Cancer Res; 23(8); 2019-26. ©2016 AACR.

Comparison between Ki67 labeling index determined using image analysis software with virtual slide system and that determined visually in breast cancer.

BACKGROUND: In recent papers, Ki67 labeling index (LI) has been used to classify breast cancer patients into the low and high Ki67LI groups for comparison studies, which showed significant differences in many prognostic factors. It has not been clarified whether image analysis software can be used for calculating LI in breast cancer. In our study, we examined whether Ki67LI in breast cancer calculated using image analysis software correlates with that measured on the basis of visual. METHODS: Fifty patients were randomly selected among breast cancer patients who underwent surgical operation from March, 2010 to May, 2010 in our hospital without preoperative chemotherapy. In this study, for the virtual slide system (VSS: VS120-L100, Olympus, Tokyo, Japan), the high-resolution VSs of all the 50 patients were prepared as samples. The image analysis software use for calculating LI was Tissuemorph Digital Pathology (Tissuemorph DP: Visiopharm, Hoersholm, Denmark). The calculated LI was extracted from 3 to 5 views containing hot spots. The LI calculated using Tissuemorph DP was designed as LI/image/T. The digital image of 3 to 5 LI/image/T views was printed out, and on the digital photograph, we counted visually the number of Ki67-immunopositive cells in exactly the same area, and the percentage of Ki67-immunopositive cells was designed as LI/direct. Moreover, a pathologist's assistant (PA) determined the tumor area in the same specimen using VSS and calculated LI using Tissuemorph DP, which was designed as LI/image/PA. The chief pathologist (CP) similarly calculated LI which was designed as LI/image/CP. We evaluated the degree of agreement between different data sets "LI/image/T and LI/direct" and "LI/image/T, LI/image/CP, and LI/image/PA" by using interclass correlation coefficient (ICC). RESULTS: The average counts of cells were as follows: LI/direct, 3209.7 ± 1970.4 (SD); LI/image/T, 2601.6 ± 1697.1; LI/image/PA, 2886.5 ± 2027.5; LI/image/CP, 18805.5 ± 22293.4. The values of LI/direct and LI/image/T showed almost perfect agreement as showed by an ICC of 0.885 (95 % CI, 0.806-0.933; p < 0.001). The agreement among three investigators was almost perfect. The obtained ICC was 0.825 (95 % CI, 0.739-0.890; p < 0.001) among the data of LI/image/T, LI/image/CP and LI/image/PA. There were five cases that immunopositivity for Ki67 showed a more than 10 % disagreement between LI/direct and LI/image/T. CONCLUSION: The merits of calculating Ki67 LI using Tissuemorph DP are as follows. First, the staining intensity of the cells to be counted can be adjusted. Second, the portion of a tumor including "hot spots" for counting can be chosen. Third, many cancer cells can be counted more rapidly using Tissuemorph DP than by visual observation. However, it is important that pathologist should check and carry out the final decision of the data, when Ki67 LI using Tissuemorph DP is calculated.

Safe and effective deodorization of malodorous fungating tumors using topical metronidazole 0.75 % gel (GK567): a multicenter, open-label, phase III study (RDT.07.SRE.27013).

PURPOSE: Malignant fungating tumors are neoplastic tumors associated with skin ulcers, which are susceptible to microbial colonization. Bacterial infection and proliferation may lead to malodor causing distress to patients. Metronidazole-an effective agent against anaerobes-may contribute to deodorization and improvement in quality of life (QOL). This study investigated the efficacy and safety of topical metronidazole 0.75 % gel for alleviation of malodor in anaerobically infected fungating neoplastic tumors. METHODS: This was a multicenter, open-label, non-controlled, phase III study including subjects aged 20 years or older with cutaneous fungating tumors releasing malodor (minimum score of 2 (mildly offensive smell) on a scale from 0 (no smell) to 4 (extremely offensive smell) based on investigator's assessment). Subjects applied metronidazole 0.75 % gel once or twice daily at the investigator's discretion for 14 days. Success was defined as an odor score of 0 or 1 at day 14, as assessed by the investigator. Patient satisfaction was assessed using a satisfaction questionnaire. Adverse events (AEs) that occurred after application of metronidazole 0.75 % gel were also reported. RESULTS: A total of 21 subjects at a median age of 65.0 years were enrolled. The success rate of deodorization at day 14 was 95.2 % (20/21 subjects). The patient satisfaction assessment showed that 71.4 % (15/21) of subjects were markedly or moderately improved. The treatment was well tolerated with only two AE cases of skin neoplasm bleeding (one mild and one moderate). CONCLUSIONS: Metronidazole 0.75 % gel is an effective and safe treatment for deodorization of malodorous fungating tumors.

Oncologic outcomes and technical considerations of nipple-sparing mastectomies in breast cancer: experience of 425 cases from a single institution.

BACKGROUND: Nipple-sparing mastectomy (NSM) is an advantageous treatment option, providing a complete cure and good cosmetic results. We tested whether NSM is a surgically and oncologically safe technique. METHODS: We evaluated the oncological outcome of 425 breasts in 413 patients who underwent NSM between January 2000 and March 2013. We retrospectively reviewed patient data and analyzed all patient characteristics as potential risk factors of recurrence at the nipple-areola complex (NAC). To confirm the oncological safety of NSM, we compared outcomes of NSM and conventional total mastectomy. RESULTS: The median follow-up time after surgery was 46.8 months (range 6-158 months). Nipple necrosis was observed in 6 cases (1.4 %). The cumulative local recurrence rate after NSM was 5.8 % (25/425 cases), similar to that of conventional total mastectomy in the same period (5.6 %, 49/878 cases). Furthermore, the cumulative local recurrence rate at the NAC was 2.3 % (10 cases). HER2-enriched tumors and young age (<40 years) were significant risk factors for recurrence at the NAC. In patients with recurrence, the site of recurrence was easily excised, and good cosmetic results were achieved in breast reconstruction cases. CONCLUSION: NSM is safe with a low complication rate. No significant difference was observed in cumulative local recurrence rate, cumulative distant disease recurrence rate, and overall survival between patients who underwent NSM or conventional total mastectomy, confirming that NSM was surgically and oncologically safe.

Positive predictive value for malignancy of pure flat epithelial atypia diagnosis by percutaneous needle biopsy of the breast: management of FEA in ultrasonography.

BACKGROUND: Some reports suggest that the rate of definitive diagnosis of malignant tumors, namely, the final diagnosis being revised to a higher stage, in patients diagnosed as having flat epithelial atypia (FEA) by percutaneous needle biopsy of the breast (PNB) is as low as 0-3 %. However, other reports suggest that the rate is as high as 10 % or more, bringing confusion on this issue. We examined the positive predictive value for malignancy in the patients diagnosed as having pure FEA and the patients' radiolopathological characteristics observed in our hospital. METHODS: Of the patients who underwent PNB in our facility, those who were diagnosed as having pure FEA were recruited as the subjects of this study. RESULTS: Of the 4,197 consecutive patients who underwent PNB, 44 (1.0 %) were diagnosed as having pure FEA following a re-examination. Among 44 cases, 39 cases were selected as the subjects of this study. Among the 39 patients, six patients were diagnosed as having malignant lesions, two of whom had invasive carcinoma of no special type (papillotubular type), one had tubular carcinoma, one had ductal carcinoma in situ (DCIS) of high nuclear grade, one had DCIS of intermediate nuclear grade, and one had DCIS of low nuclear grade. The diameters of 6 malignant lesions were 10-30 mm at ultrasonography (US) examination. Five of the 39 patients had contralateral breast cancer. CONCLUSION: The positive predictive value for malignancy of pure FEA was 15.7 %. The patients with pure FEA may make a follow up without an excisional biopsy when the lesion sizes less than 10 mm on US examination.

Activation of an estrogen/estrogen receptor signaling by BIG3 through its inhibitory effect on nuclear transport of PHB2/REA in breast cancer.

Breast cancer is known to be a hormone-dependent disease, and estrogens through an interaction with estrogen receptor (ER) enhance the proliferative and metastatic activity of breast tumor cells. Here we show a critical role of transactivation of BIG3, brefeldin A-inhibited guanine nucleotide-exchange protein 3, in activation of the estrogen/ER signaling in breast cancer cells. Knocking-down of BIG3 expression with small-interfering RNA (siRNA) drastically suppressed the growth of breast cancer cells. Subsequent coimmunoprecipitation and immunoblotting assays revealed an interaction of BIG3 with prohibitin 2/repressor of estrogen receptor activity (PHB2/REA). When BIG3 was absent, stimulation of estradiol caused the translocation of PHB2/REA to the nucleus, enhanced the interaction of PHB2/REA and ERalpha, and resulted in suppression of the ERalpha transcriptional activity. On the other hand, when BIG3 was present, BIG3 trapped PHB2/REA in the cytoplasm and inhibited its nuclear translocation, and caused enhancement of ERalpha transcriptional activity. Our results imply that BIG3 overexpression is one of the important mechanisms causing the activation of the estrogen/ERalpha signaling pathway in the hormone-related growth of breast cancer cells.

Involvement of G-patch domain containing 2 overexpression in breast carcinogenesis.

Through analysis of the detailed genome-wide gene expression profiles of 81 breast tumors, we identified a novel gene, G-patch domain containing 2 (GPATCH2), that was overexpressed in the great majority of breast cancer cases. Treatment of breast cancer cells MCF-7 and T47D with siRNA against GPATCH2 effectively suppressed its expression, and resulted in the growth suppression of cancer cells, suggesting its essential role in breast cancer cell growth. We found an interaction of GPATCH2 protein with hPrp43, an RNA-dependent ATPase. Their interaction could significantly enhance the ATPase activity of hPrp43 and induce a growth-promoting effect on mammalian cells. Because northern blot analyses of normal human organs implied GPATCH2 to be a novel cancer/testis antigen, targeting GPATCH2 or inhibition of the interaction between GPATCH2 and hPrp43 could be a promising novel therapeutic strategy of breast cancer.

Involvement of kinesin family member 2C/mitotic centromere-associated kinesin overexpression in mammary carcinogenesis.

To elucidate the molecular mechanisms of mammary carcinogenesis and discover novel therapeutic targets for breast cancer, we previously carried out genome-wide expression profile analysis of 81 breast cancer cases by means of cDNA microarray coupled with laser microbeam microdissection of cancer cells. Among the dozens of transactivated genes, in the present study we focused on the functional significance of kinesin family member 2C (KIF2C)/mitotic centromere-associated kinesin (MCAK) in the growth of breast cancer cells. Northern blot and immunohistochemical analyses confirmed KIF2C/MCAK overexpression in breast cancer cells, and showed that it is expressed at undetectable levels in normal human tissues except the testis, suggesting KIF2C/MCAK to be a cancer-testis antigen. Western blot analysis using breast cancer cell lines revealed a significant increase in the endogenous KIF2C/MCAK protein level and its phosphorylation in G(2)/M phase. Treatment of breast cancer cells with small interfering RNA against KIF2C/MCAK effectively suppressed KIF2C/MCAK expression and inhibited the growth of the breast cancer cell lines T47D and HBC5. In addition, we found that KIF2C/MCAK expression was significantly suppressed by ectopic introduction of p53. These findings suggest that overexpression of KIF2C/MCAK might be involved in breast carcinogenesis and is a promising therapeutic target for breast cancers.

Oncogenic role of MPHOSPH1, a cancer-testis antigen specific to human bladder cancer.

To disclose the molecular mechanism of bladder cancer, the second most common genitourinary tumor, we had previously done genome-wide expression profile analysis of 26 bladder cancers by means of cDNA microarray representing 27,648 genes. Among genes that were significantly up-regulated in the majority of bladder cancers, we here report identification of M-phase phosphoprotein 1 (MPHOSPH1) as a candidate molecule for drug development for bladder cancer. Northern blot analyses using mRNAs of normal human organs and cancer cell lines indicated this molecule to be a novel cancer-testis antigen. Introduction of MPHOSPH1 into NIH3T3 cells significantly enhanced cell growth at in vitro and in vivo conditions. We subsequently found an interaction between MPHOSPH1 and protein regulator of cytokinesis 1 (PRC1), which was also up-regulated in bladder cancer cells. Immunocytochemical analysis revealed colocalization of endogenous MPHOSPH1 and PRC1 proteins in bladder cancer cells. Interestingly, knockdown of either MPHOSPH1 or PRC1 expression with specific small interfering RNAs caused a significant increase of multinuclear cells and subsequent cell death of bladder cancer cells. Our results imply that the MPHOSPH1/PRC1 complex is likely to play a crucial role in bladder carcinogenesis and that inhibition of the MPHOSPH1/PRC1 expression or their interaction should be novel therapeutic targets for bladder cancers.

Elevated expression of protein regulator of cytokinesis 1, involved in the growth of breast cancer cells.

To elucidate molecular mechanisms of mammary carcinogenesis and discover novel therapeutic targets for breast cancer, we previously carried out a genome-wide expression profile analysis of 81 breast cancer cases by means of a combination of cDNA microarray and laser microbeam microdissection. Among the upregulated genes, we focused on the functional significance of protein regulator of cytokinesis 1 (PRC1) in the development of breast cancer. Western blot analysis using breast cancer cell lines revealed a significant increase in endogenous PRC1 levels in G(2)/M phase. Treatment of breast cancer cells with small interfering RNA against PRC1 effectively suppressed its expression and inhibited the growth of breast cancer cell lines T47D and HBC5. Furthermore, we found an interaction between PRC1 and kinesin family member 2C/mitotic centromere-associated kinesin (KIF2C/MCAK) by coimmunoprecipitation and immunoblotting using COS-7 cells, in which these molecules were introduced exogenously. These findings suggest the involvement of a PRC1-KIF2C/MCAK complex in breast tumorigenesis, and this complex should be a promising target for the development of novel treatments for breast cancer.