Parathyroid hormone-related protein localization in breast cancers predict improved prognosis

In a prospective study of 526 consecutive patients with operable breast cancer, the significance of positive parathyroid hormone-related protein (PTHrP) staining by immunohistology has been evaluated for a median of 10-year follow-up. Improved survival was observed for the 79% of tumors which stained positively for PTHrP [estimated univariate hazard ratio, 0.43; 95% confidence interval (95% CI), 0.30-0.62; P < 0.001]. Adjustments for N stage, progesterone receptor status, and log tumor size changed this estimate only slightly to 0.47 (95% CI, 0.63-0.69; P = 0.001). Patients with PTHrP-positive primary tumors were less likely to develop bone metastases (hazard ratio, 0.63; 95% CI, 0.41-0.98; P = 0.04). PTHrP status was associated with estrogen receptor (P = 0.01), progesterone receptor (P = 0.03), and menopausal status (P = 0.006) but was not significantly associated with tumor size, vascular invasion, tumor grade, or patient age. Of 19 patients requiring surgery for bone metastases, the primary cancers were PTHrP negative in seven, all but one of whom had PTHrP-positive bone metastases. All 12 patients with PTHrP-positive primary cancers also had positive bone metastases. We conclude that increased production of PTHrP by breast cancers confers on them a less invasive phenotype, an effect distinct from the bone resorption-stimulating action that favors bone metastasis. It is likely that the latter property is influenced by factors in the bone microenvironment.     

Elevated expression of cyclooxygenase-2 is a negative prognostic factor for disease free survival and overall survival in patients with breast carcinoma

BACKGROUND: Cyclooxygenases regulate the production of prostaglandins and play a role in tumor development and progression. The authors investigated the prognostic impact of expression of the cyclooxygenase (COX) isoforms, COX-1 and COX-2, on disease-free survival and progression-free survival in patients with primary breast carcinoma as well as the association between COX expression and other clinicopathologic parameters. METHODS: In this study COX isoform expression was determined by immunohistochemistry in a cohort of 221 patients with primary breast carcinoma. RESULTS: Expression of COX-2 was detected in 36% of breast carcinoma samples and was associated significantly with several clinicopathologic parameters, including positive lymph node status (P < 0.0005), larger tumor size (P < 0.0005), poor differentiation (P < 0.0005), vascular invasion (P = 0.03), and negative estrogen receptor status (P = 0.04). In contrast, COX-1 was expressed in 45% of tumors and was associated with smaller tumor size (P = 0.02) and with negative lymph node status (P = 0.01). In a univariate survival analysis, a significant association was observed between elevated COX-2 expression and decreases in disease-free survival (P = 0.0007) and overall survival (P = 0.02). In a multivariate analysis, expression of COX-2 was of borderline significance for disease-free survival (relative risk, 1.90; 95% confidence interval, 1.00-3.59), adjusting for tumor size, histologic grade, number of positive lymph nodes, and patient age. Elevated expression of COX-1 in tumor tissue had no statistically significant influence on patient prognosis. CONCLUSIONS: The current data suggest that increased expression of COX-2 may play a role in the progression of primary breast carcinoma. It remains to be investigated whether treatment with selective inhibitors of COX-2 may be an additional therapeutic option for patients with breast carcinoma.     

Prognostic significance of c-erbB-2 and estrogen receptor status in human breast cancer.

Using the 21N polyclonal antibody, we immunohistochemically stained 314 primary breast carcinomas to identify those tumors overexpressing the c-erbB-2 oncoprotein and to ascertain the prognostic significance of this expression on disease-free and overall survival. Positive membrane staining was present in 52 (17%) of these carcinomas of which 7 (13%) were ductal carcinomas in situ. There was no significant relationship between c-erbB-2 positivity and (a) age at diagnosis, (b) menopausal status, (c) tumor size, (d) lymph node status, (e) estrogen receptor status, or (f) whether or not the patient had disseminated disease outside the axillary fields. However, c-erbB-2-positive tumors were significantly associated with poorer grade (P = 0.02). Patients who were positive for this oncoprotein had a shorter disease-free survival (P = 0.002) and reduced overall survival (P = 0.0001). Overexpression of this oncoprotein was predictive of a worse prognosis in lymph node-positive disease (P = 0.003) and in patients presenting with grade II tumors (P = 0.001). Stratifying the patients on the basis of estrogen receptor status suggested that c-erbB-2+/estrogen receptor-negative status was predictive of a poorer prognosis when compared with the other subgroups (P less than 0.001). Primary and recurrent tumor tissues were available from 42 of the 314 patients. Identical patterns of c-erbB-2 expression occurred in 95% of cases, arguing against a direct role for c-erbB-2 expression in the process of tumor dissemination. The high incidence of staining in ductal carcinomas in situ suggests that expression of this oncoprotein is an early event in tumorigenesis. Finally, multivariate analysis indicated that the c-erbB-2 oncoprotein was an independent prognostic indicator for overall survival in breast carcinoma patients.     

Parathyroid hormone-related protein expression is correlated with clinical course in patients with glial tumors

BACKGROUND: Parathyroid hormone-related protein (PTHrP) expression modulates cell survival in a number of human solid tumors. Although PTHrP is expressed in normal developing and neoplastic central nervous system tissue, clinical data indicating the importance of this protein with respect to local control and/or survival in patients with glial tumors are scarce. METHODS: Using a standard immunoperoxidase technique, the authors examined PTHrP expression in a population of 51 patients with Daumas-Duport Grade II-IV astrocytomas over a 15-year period. Both local control and survival were calculated from the date of definitive irradiation to the last time of known follow-up examination using the actuarial method. PTHrP expression was scored on examination under 40x magnification, with the incidence of cellular staining averaged over 10 high-power fields. The intensity and extent of staining were characterized semiquantitatively using the standard World Health Organization classification criteria. The median follow-up duration was approximately 5.5 years. Multivariate analyses were performed to ascertain the statistical significance of several standard clinicohistopatholgic factors (Karnofsky functional status, age, gender, extent of surgical resection, radiotherapy dose, grade, and PTHrP expression) with respect to local control and survival. P < 0.05 was considered indicative of statistical significance. RESULTS: Patients with high levels of PTHrP expression had significantly lower glial tumor local control rates and corresponding decreases in progression-free and overall actuarial survival after definitive irradiation (P < 0.01). In a Cox 3-variable model, the PTHrP staining score was independent of tumor grade or Karnofsky functional status. It is notable that the strongest predictor of survival was tumor grade (P < 0.001). CONCLUSIONS: PTHrP may be an important adjunct to standard immunopathologic criteria in the determination of glial tumor responses. A number of mechanisms were explored to derive a more mechanistic understanding of these translational results. Subsequent prospective studies involving larger patient populations will be necessary before findings can be translated to clinical practice.     

Expression of BAG-1 in invasive breast carcinomas.

PURPOSE: The purpose of this study was to retrospectively evaluate the expression of BAG-1 in invasive breast carcinomas. The intensity and subcellular distribution of BAG-1 expression was correlated with conventional prognostic factors and with disease-free and overall survival. PATIENTS AND METHODS: One hundred forty patients diagnosed with invasive breast cancer in St. John's, Newfoundland, between 1986 and 1996 were included in the study. The median follow-up of the study was 8 years. Expression of BAG-1 was determined by immunohistochemical staining of paraffin-embedded breast tumor tissues. RESULTS: Of the 140 breast carcinomas examined, 77.1% were positive for BAG-1 expression. Except for differentiation, no correlation was observed between BAG-1 expression and conventional prognostic factors such as age, histology, stage, and estrogen and progesterone receptor status. In multivariate analysis, BAG-1 expression was significantly associated with shorter disease-free (P =.0052) and overall survival (P =.0033). Patients whose tumors expressed nuclear BAG-1 tended to have a shorter disease-free (63 v 84 months; P = 0.4493) and overall (69 v 99 months, P =.1009) survival. CONCLUSION: BAG-1 is overexpressed in the majority of invasive breast carcinomas. Although BAG-1 did not correlate with conventional prognostic factors, its overexpression, especially the nuclear expression, may be associated with a shorter disease-free and overall survival. Our preliminary data strongly indicate that further investigation is warranted to define the role of BAG-1 as an independent prognostic factor in patients with newly diagnosed breast cancer.     

Women age < or = 35 years with primary breast carcinoma: disease features at presentation

BACKGROUND: The purpose of the current study was to describe a population of young patients with breast carcinoma, their characteristics at the time of diagnosis, and the association of these characteristics with disease recurrence and survival. METHODS: Four hundred fifty-two women age < or = 35 years with breast carcinoma were registered at The University of Texas M. D. Anderson Cancer Center (Houston, TX) between 1990 and 2002. The relation between clinicopathologic factors and disease recurrence-free survival (RFS) and overall survival (OS) was assessed. Cox regression analysis was used to identify independent survival predictors. RESULTS: The median age of the patients was 32 years. Most of the patients were white, and 20% were obese. Approximately 50% reported oral contraceptive use, 34% reported a family history of breast carcinoma, and 5% reported a family history of ovarian carcinoma. Sixty-nine percent of tumors were nuclear Grade 3 (using the modified Black's nuclear grading system), 52% had positive estrogen receptors, and 48% had positive progesterone receptors. HER-2/neu status was available in 60% of tumor specimens and 34% were HER-2/neu positive. The median follow-up was 36 months. There were 185 disease recurrences and 84 deaths. RFS was significantly shorter in patients who reported a family history of ovarian carcinoma (P < 0.0001) and in those who had hormone receptor-negative tumor specimens (P = 0.001). OS was significantly shorter in patients who reported a family history of ovarian carcinoma (P = 0.001), those who had hormone receptor-negative tumor specimens (P < 0.0001), or those with > nuclear Grade 3 tumor specimens (P = 0.005). CONCLUSIONS: This young population with breast carcinoma was found to have more aggressive biologic features. Hormone receptor negativity and a family history of ovarian carcinoma were associated with shorter RFS and OS.     

Prognostic significance of dysadherin expression in cervical squamous cell carcinoma

The protein and mRNA expression of dysadherin was studied in a series of squamous cell cervical carcinomas, and their clinicopathological associations and prognostic value were explored. Immunohistochemistry was used to assess protein expression of dysadherin in 206 patients with squamous cell cervical carcinoma, FIGO stage Ia-IVb. Frozen tissues from 20 cases in which the tumors showed variable dysadherin protein expression were used for laser capture microdissection (LCM) and processed for RTPCR detection of dysadherin mRNA. Immunohistochemically, all the dysadherin-positive staining was membranous. Positive cell membranous dysadherinpositive staining was often observed at the edge of tumor nests, although strong immunoreactivity throughout whole tumor nests was also seen in some tumors. Basal cells of the normal cervical epithelia were positive for dysadherin while its expression in the squamous cell cervical carcinomas was variable. Among the 206 tumors, 23 (11.2%) were negative, 53 (25.7%) were scored 1+, 54 (26.2%) were scored 2+ and 76 (36.9%) were scored 3+. In the 20 tumors analyzed, mRNA expression of dysadherin basically corresponded to its protein expression. No significant correlation between expression of dysadherin and age, FIGO stage or lymph node status was observed. Higher level of dysadherin expression, however, was significantly associated with shorter overall survival (p=0.04). We conclude that there is dysadherin protein expression in basal and parabasal cells of normal cervical epithelia, and higher level of dysadherin protein expression in squamous cell cervical carcinoma is predictive of a shorter overall survival, indicating that dysadherin may be a valuable prognostic marker in cervical carcinoma.     

The impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen treatment in breast cancer patients

Tamoxifen is a standard therapeutical treatment in patients with estrogen receptor positive breast carcinoma. However, less than 50% of estrogen receptor positive breast cancers do not respond to tamoxifen treatment whereas 40% of tumors that initially respond to treatment develop resistance over time. The underlying mechanisms for tamoxifen resistance are probably multifactorial but remain largely unknown. The primary aim of this study was to investigate the impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen by analyzing loss of heterozygosity (LOH) and immunohystochemical expression of PTEN in 49 primary breast carcinomas of patients treated with tamoxifen as the only adjuvant therapy. The effect of PTEN inactivation on breast cancer progression and disease outcome was also analyzed. Reduced or completely lost PTEN expression was observed in 55.1% of samples, while 63.3% of samples displayed LOH of PTEN gene. Inactivation of PTEN immunoexpression significantly correlated with the PTEN loss of heterozygosity, suggesting LOH as the most important genetic mechanism for the reduction or complete loss of PTEN expression in primary breast carcinoma. Most importantly, LOH of PTEN and consequential reduction of its immunoexpression showed significant correlation with the recurrence of the disease. Besides, our study revealed that LOH of PTEN tumor suppressor was significantly associated with shorter disease free survival, breast cancer specific survival and overall survival. In summary, our results imply that LOH of PTEN could be used as a good prognostic characteristic for the outcome of breast cancer patients treated with tamoxifen.     

The importance of MUC1 cellular localization in patients with breast carcinoma: an immunohistologic study of 71 patients and review of the literature

BACKGROUND: The MUC1 mucin is present on the apical surface of normal secretory epithelia. In breast carcinoma, MUC1 expression is variable in amount and cellular localization, the significance of which is controversial. The authors undertook a detailed analysis of staining pattern combined with a comprehensive literature review to better understand the role of MUC1 in breast carcinoma. METHODS: Seventy-one patients with breast carcinoma were examined for MUC1, beta-catenin, and E-cadherin staining patterns. These data were compared with data from 25 articles from the literature examining the expression of MUC1 in breast carcinoma. RESULTS: All invasive carcinomas showed some MUC1 staining. In invasive ductal carcinomas, MUC1 was detected in the apical membrane (15%), cytoplasm (93%), or circumferential membrane (13%), with 81% of tumors showing a mixture of patterns. Tumors with low overall MUC1 expression (< or = 50% positive tumor cells) had a higher nuclear grade than tumors with high overall MUC1 expression (> 50%; P = 0.01). Tumors with high and low cytoplasmic expression had no difference in nuclear grade (P > 0.3). Circumferential membrane staining was correlated with positive lymph node status (P = 0.011). CONCLUSIONS: In the literature, similar findings prevailed in which overall MUC1 expression was increased in lower grade (10 of 14 studies), estrogen receptor positive (8 of 13 studies) tumors and was associated with a better prognosis (8 of 13 studies). High cytoplasmic staining was associated with a worse prognosis, an association that was not explained by differences in histologic grade. Thus, the presence of MUC1 in the majority of tumor cells is associated with better differentiated tumors and with an improved prognosis. However, aberrantly localized MUC1 in the tumor cell cytoplasm or nonapical membrane is associated with a worse prognosis.     

STK15/Aurora-A expression in primary breast tumors is correlated with nuclear grade but not with prognosis

BACKGROUND: DNA amplification on chromosome 20q13 is commonly detected in breast carcinoma and is correlated with poor prognosis. STK15 maps to this amplicon. The objective of the current study was to use immunohistochemistry to determine STK15 expression in primary breast tumors. The authors also explored whether STK15 was a prognostic factor for breast carcinoma by comparing the level of STK15 gene expression with clinical parameters that are known prognostic factors for the disease. METHODS: Archival mastectomy and lumpectomy specimens, randomly selected, were immunohistochemically stained to determine the STK15 gene expression level. The clinical parameters of these same patients were reviewed retrospectively and analyzed for correlations with STK15 expression level, based on a positive-versus-negative scoring system. RESULTS: Of the 112 human breast tumor specimens analyzed, 26% stained positively for STK15 by immunohistochemistry. Of the tumors, that stained positively 62.1% had a well-to-moderately differentiated nuclear grade. The correlation between STK15 staining and nuclear grade was nearly statistically significant (P = 0.05). No association was found between STK15 staining and tumor size, lymph node status, or hormone receptor status. Analysis of recurrence-free survival and overall survival rates also failed to reveal a statistically significant difference between the two groups. CONCLUSIONS: STK15 expression by immunohistochemistry was noted in approximately one-fourth of primary breast tumors. STK15 expression was associated with nuclear grade, but no correlation was found between the other clinical parameters evaluated. Furthermore, no differences were found in survival rates when they were analyzed by level of STK15 staining.     

Luteinizing hormone receptor status and clinical,pathologic, and prognostic features in patients with breast carcinomas

BACKGROUND: It has been established that pregnancy protects against breast carcinoma, and animal models have shown that human chorionic gonadotropin (hCG) mimics this effect by inhibiting the initiation and progression of experimental breast carcinoma. Luteinizing hormone (LH)/hCG receptors (LHR) have been characterized in several human breast carcinoma cell lines and in a limited number of breast carcinoma biopsy specimens. These observations led to the suggestion that hCG may be used as a means of prevention and possibly treatment in patients with breast carcinoma. METHODS: The authors used immunocytochemistry to analyze tumors from 160 patients who were followed for a median of 2539 days. Using a cut-off value of 18% immunolabeled cells in each tumor, 72% of tumors were identified as LHR positive. The LHR-positive tumors were found more frequently in premenopausal women, who had tumors with greater cell differentiation and positive estrogen receptor alpha status. Infiltrating lobular carcinomas were positive for LHR more frequently compared with infiltrating ductal carcinomas. There was no correlation between LHR status and lymph node invasion, tumor size, or progesterone receptor status. RESULTS: Patients with LHR-positive tumors had a longer metastasis free survival, although the statistical significance was slight (P = 0.07), most likely due to the limited number of events in the patients studied. Conversely, there was no difference between patients with LHR-positive or LHR-negative tumors in the local recurrence free interval. CONCLUSIONS: LHR status seems to be related in part to the degree of differentiation in breast tumors, confirming experimental evidence of the effect of hCG on mammary tissue. The presence of LHR is a tumor characteristic that largely is independent of other clinical and pathologic tumor features. It may be of interest in the future to correlate the presence of LHR with a possible therapeutic response in individual patients to hCG.     

Survival of patients with metastatic breast carcinoma: importance of prognostic markers of the primary tumor

BACKGROUND: Women with metastatic breast carcinoma have a highly variable clinical course and outcome. Intrinsic genetic heterogeneity of the primary breast tumor may play a role in this variability and may explain it in part. Therefore, the authors tested the hypothesis that the characteristics of primary breast tumors are important determinants of prognosis and survival in patients with metastatic breast carcinoma. METHODS: The prognostic significance of the biology of the primary tumor for outcome in patients with metastatic breast disease was assessed in 346 patients with lymph node positive breast carcinoma who developed distant, recurrent disease. Traditional prognostic indicators (age, tumor size, number of involved lymph nodes, sites of recurrence, disease free interval [DFI], adjuvant treatments, estrogen receptor [ER] expression, progesterone receptor [PgR] expression, S-phase fraction [SPF], and DNA ploidy), together with three newer biologic markers (c-erbB-2, p53, and bcl-2) were assessed. Sites of recurrence were defined as nonvisceral (bone and locoregional lymph nodes) or visceral (lung, liver, brain, and other organs). RESULTS: The median duration of survival was 17.8 months (95% confidence interval, 15.2-21.5 months). Univariate analysis showed that age > 50 years, visceral disease, and shorter DFI were associated significantly with poor outcome (P < 0.05). In addition, the molecular phenotype of the primary breast tumor was significant, with primary tumors that showed ER negativity and PgR negativity, high SPF, aneuploidy, accumulation of p53 protein, and lower bcl-2 expression, together with c-erbB-2 overexpression, all associated with a poorer clinical outcome (P < 0.05). In a multivariate analysis, older age, visceral disease, shorter DFI, PgR negativity, high SPF, and lower bcl-2 expression were significant predictors of worse survival (P < 0.05). CONCLUSIONS: In addition to traditional risk factors, bcl-2 negativity was associated significantly with a worse clinical outcome. Biologic features of primary tumors were correlated independently with outcome after first recurrence in patients with metastatic breast carcinoma and may be used as indicators of prognosis in the metastatic setting.     

基质金属蛋白酶-2在淋巴结阴性乳腺癌中的表达及临床意义

目的 探讨淋巴结阴性乳腺癌组织中基质金属蛋白酶-2(MMP-2)的表达水平、与其他因子的关系及临床意义。方法：采用免疫组织化学ABC法，检测270例淋巴结阴性乳腺癌石蜡标本中MMP-2的表达水平：结果：270例淋巴结阴性乳腺癌标本中MMP-2阳性表达为56．7％。MMP-2阳性表达与肿瘤大小和分级有关，与雌、孕激素受体(ER、PR)等因子无关；与无复发生存率(RFS)有关，而与总生存率(OS)无关：结论：MMP-2蛋白在淋巴结阴性乳腺癌转移复发中起着重要作用，是重要的预后因子：     

Prognostic impact of cyclin-dependent kinase inhibitor p27kip1 in node-positive breast cancer

BACKGROUND AND OBJECTIVES: p27kip1 (p27) plays an important role as a negative regulator of cell cycle-dependent kinase activity during progression of the cell cycle. The most important prognosticator of breast cancer is nodal status, and the aim of this study was to determine the prognostic implication of p27 in breast cancer patients with lymph node metastases. METHODS: Immunohistochemical staining for p27 was performed on tissues from 102 patients with node-positive breast cancer. RESULTS: A nuclear staining over 50% was defined as high expression. High expression of p27 was shown in 59 patients (57.8%). A significant correlation was found between high p27 and positive estrogen receptor status, but there was no correlation between p27 staining and age, menopausal status, nodal status, or tumor size. Low expression of p27 was significantly associated with shorter survival. A multivariate analysis also showed that the only independent variable was p27. CONCLUSIONS: The results indicated that low expression of p27 was an independent factor associated with poor prognosis. Therefore, p27 can be an important tool in making therapeutic decisions.     

Mutual predictive value of c-erbB-2 overexpression and various prognostic factors in ductal invasive breast carcinoma

AIMS AND BACKGROUND: Breast carcinoma is a heterogeneous disease, the prognosis of which correlates with various prognostic factors. The aim of this study was to assess the prognostic significance of c-erbB-2 overexpression in breast carcinoma patients in association with other known prognostic factors. METHODS & STUDY DESIGN: The relationship between immunohistochemical expression of the c-erbB-2 oncoprotein and various established prognostic factors such as tumor size, axillary node status, estrogen and progesterone receptor status, DNA ploidy, proliferation index, cathepsin D expression and histological grade in invasive ductal breast carcinoma is presented in this study. RESULTS: Of the 93 ductal invasive carcinomas 22 (23.7%) were grade I, 51 (54.8%) grade II, and 20 (21.5%) grade III, and the majority (78: 83.9%) were 2-5 cm in diameter. Tumor metastases were identified in one or more lymph nodes in 55 (59.1%) patients, the remaining 38 (40.9%) patients being lymph node negative. According to the DNA histograms 40 (43.0%) tumors were aneuploid and 53 (57.0%) were diploid, and the majority of tumors had more than 4% of cells in the S phase of the cell cycle (83.9%). Expression of c-erbB-2 as shown by immunohistochemical intense membrane staining was present in 49 (52.7%) tumors. Cathepsin D-positive cytoplasmic granular staining and cathepsin D-positive stromal macrophages were found in 60 (64.5%) and 72 (77.4%) tumors, respectively. Univariate analysis showed that overall survival correlated significantly with axillary lymph node involvement and with estrogen and progesterone receptor status for each of the receptors separately and for their coexpression, and only marginally with c-erbB-2 overexpression. In mulitivariate analysis only axillary lymph node metastases and coexpression of estrogen and progesterone receptors were found to be independent and significant prognostic factors. CONCLUSIONS: When patients were stratified according to c-erbB-2 expression it was shown that those with c-erbB-2 overexpression and grade II tumors, tumor size greater than 2 cm, high content of aneuploid cells and cathepsin D-positive stromal macrophages had a shorter long-term survival than c-erbB-2 negative patients.     

dUTP nucleotidohydrolase isoform expression in normal and neoplastic tissues: association with survival and response to 5-fluorouracil in colorectal cancer

Aberrant dUTP metabolism plays a significant role in the underlying molecular mechanisms of cell killing mediated by inhibitors of thymidylate biosynthesis. dUTP nucleotidohydrolase (dUTPase) is the key regulator of dUTP pools, and significant evidence exists suggesting that the expression of this enzyme may be an important determinant of cytotoxicity mediated by inhibitors of thymidylate synthase (TS). In this study, we have determined the expression patterns of dUTPase in normal and neoplastic tissues and examined the association between dUTPase expression and response to 5-fluorouracil (5-FU)-based chemotherapy and overall survival in colorectal cancer. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections using a monoclonal antibody (MAb), DUT415, that cross-reacts with both nuclear and mitochondrial isoforms of human dUTPase. Nuclear and cytoplasmic staining was observed in both normal and neoplastic tissues. In normal tissues, nuclear dUTPase staining was observed exclusively in replicating cell types. This observation is in agreement with cell culture studies where expression of the nuclear isoform (DUT-N) is proliferation dependent In contrast, cytoplasmic expression of dUTPase does not correlate with proliferation status and was observed in tissues rich in mitochondria. Consistent with this observation, cell culture studies reveal that the mitochondrial isoform (DUT-M) is expressed constitutively, independent of cell cycle status. These data suggest that in normal tissues, nuclear staining with the DUT415 antibody represents the DUT-N isoform, whereas cytoplasmic staining represents the DUT-M isoform. In colon cancer tumor specimens, expression of dUTPase was shown to be highly variable in both amount and intracellular localization. Patterns of dUTPase protein expression observed included exclusive nuclear, exclusive cytoplasmic, and combined nuclear and cytoplasmic staining. Thus, immunohistochemical detection of dUTPase in colon cancers provides distinct intracellular phenotypes of expression that may be of significant prognostic value. To examine the association between dUTPase expression and response to 5-FU-based chemotherapy and overall survival, we initiated a retrospective study including tumor specimens from 20 patients who had received protracted infusion of 5-FU and leucovorin for treatment of metastatic colon cancer. Positive nuclear staining was found in 8 patients, whereas 12 lacked nuclear expression. Of the patients lacking nuclear dUTPase expression, 6 responded to 5-FU-based chemotherapy, 4 had stable disease, and 2 had progressive disease. Of the patients presenting positive nuclear dUTPase expression, 0 responded to chemotherapy, 1 had stable disease, and 7 had progressive disease (P = 0.005). The median survival for patients with tumors lacking nuclear staining was 8.5 months and 6.9 months for patients with tumors demonstrating positive nuclear dUTPase expression (P = 0.09). Time to progression was significantly longer for patients with tumors lacking nuclear staining (P = 0.017). Variable cytoplasmic dUTPase expression was observed in these tumors; however, there was no apparent association with clinical response or survival in this limited study. Nuclear dUTPase staining within these tumors was also associated with TS gene expression (P = 0.06). This study demonstrates that low intratumoral levels of nuclear dUTPase protein expression is associated with response to 5-FU-based chemotherapy, greater time to progression, and greater overall survival in colorectal cancer. Conversely, high levels of nuclear dUTPase protein expression predict for tumor resistance to chemotherapy, shorter time to progression, and shorter overall survival. This report represents the first clinical study implicating dUTPase overexpression as a mechanism of resistance to TS inhibitor-based chemotherapy.