Enzyme-linked immunosorbent assay of HER-2/neu gene product (p185) in breast cancer: its correlation with sex steroid receptors, cathepsin D and histologic grades

Stepping forward in antibody-drug conjugate development

Antibody-drug conjugates (ADCs) are cancer therapeutic agents comprised of an antibody, a linker and a small-molecule payload. ADCs use the specificity of the antibody to target the toxic payload to tumor cells. After intravenous administration, ADCs enter circulation, distribute to tumor tissues and bind to the tumor surface antigen. The antigen then undergoes endocytosis to internalize the ADC into tumor cells, where it is transported to lysosomes to release the payload. The released toxic payloads can induce apoptosis through DNA damage or microtubule inhibition and can kill surrounding cancer cells through the bystander effect. The first ADC drug was approved by the United States Food and Drug Administration (FDA) in 2000, but the following decade saw no new approved ADC drugs. From 2011 to 2018, four ADC drugs were approved, while in 2019 and 2020 five more ADCs entered the market. This demonstrates an increasing trend for the clinical development of ADCs. This review summarizes the recent clinical research, with a specific focus on how the in vivo processing of ADCs influences their design. We aim to provide comprehensive information about current ADCs to facilitate future development.

A nomogram to predict HER2 status in breast cancer patients with HER2-borderline disease as determined via immunohistochemistry

This study aimed to develop a nomogram to predict fluorescence in situ hybridization (FISH) assay results for HER2-borderline breast cancer as determined via immunohistochemistry (IHC) among patients in China. We reviewed a database of breast cancer patients diagnosed between January 2007 and April 2013 at our institutions. We used logistic regression to develop a nomogram and we used receiver operating characteristic curve analysis and calibration plots to validate our nomogram. In total, 1138, 301 and 344 patients had IHC-determined HER2-negative, HER2-borderline and HER2-positive disease, respectively. Within the training cohort, univariate and multivariate analyses suggested that estrogen receptor (ER) status, progesterone receptor (PR) status and tumor grade were significantly associated with HER2 status (P<0.01). A nomogram was developed and the AUCs for the training and validation cohorts were 0.795 and 0.749, respectively. The calibration plots suggested that the model was well calibrated. This new nomogram can be used to predict HER2 status in HER2-borderline breast cancer patients and will be particularly helpful to resource-limited countries.

Human epidermal growth factor receptor-2-positive breast cancer: does estrogen receptor status define two distinct subtypes?

BACKGROUND

Human epidermal growth factor receptor-2 (HER2) overexpression occurs in ∼20% of breast cancers and has historically been associated with decreased survival. Despite substantial improvements in clinical outcomes, particularly with the emergence of HER2-targeted therapy, a substantial minority of patients still relapses, and progression is inevitable in metastatic disease. Accumulating data indicate that HER2-positive disease is itself a heterogeneous entity.

METHODS AND RESULTS

In this article, we qualitatively review the data supporting the classification of HER2-positive disease as at least two separate entities, distinguished by estrogen receptor (ER) status. We summarize differences in clinical outcomes, including response to neoadjuvant therapy, timing and patterns of dissemination, efficacy of therapy in the metastatic setting and survival outcomes.

CONCLUSIONS

The collective data are sufficiently strong at this point to propose that ER status defines two distinct subtypes within HER2-positive breast cancer, and we highlight the implications of this knowledge in future research, including understanding of the basic biology of HER2-positive breast cancer and the design of future clinical trials.

The epidermal growth factor receptor family in breast cancer

THE HUMAN EPIDERMAL GROWTH FACTOR RECEPTOR (HER) FAMILY COMPRISES FOUR HOMOLOGOUS MEMBERS: EGFR, HER-2, HER-3, and HER-4. The activation of these receptors triggers a complex series of signal transduction pathways which affect pivotal tumorigenic processes. The deregulation of HER signaling is seen in several human malignancies. HER-2 is now recognized as a key oncogene in breast cancer pathogenesis. Assessment of HER-2 status is of central importance in the prognosis of breast cancer patients. In the light of clinical data suggesting that HER-2 can also be useful as a predictive marker both for trastuzumab and chemotherapy, standardized determination of the HER-2 status in tumors has become more important. Moreover, current data provide evidence for the significance of HER-3 and HER-4 alterations in breast carcinogenesis. Because of the complex interactions among the HER receptors, it is likely that the effect on cell proliferation and tumor growth depends on receptor trans-signaling and thus, the evaluation of the combined expression pattern of all family members is of particular interest. This review presents the current evidence highlighting the role of the family as a whole panel and an update on the role of HER-3 and HER-4 receptors in breast cancer. Moreover, we provide updated data regarding the prognostic value of HER family members giving emphasis to novel methods for the determination of their status, such as real-time polymerase chain reaction. In addition, we review recent therapeutic approaches aimed at targeting the HER family in breast cancer patients.

Human epidermal growth factor receptor-2 and estrogen receptor expression, a demonstration project using the residual tissue repository of the Surveillance, Epidemiology, and End Results (SEER) program

BACKGROUND

In 2001, the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program established Residual Tissue Repositories (RTR) in the Hawaii, Iowa, and Los Angeles Tumor Registries to collect discarded tissue blocks from pathologic laboratories within their catchment areas. To validate the utility of the RTR for supplementing SEER's central database, we assessed human epidermal growth factor receptor-2 (HER2) and estrogen receptor expression (ER) in a demonstration project.

MATERIALS

Using a prepared set of tissue microarrays (TMAs) residing in the Hawaii Tumor Registry (HTR), we performed standard immunohistochemistry. Breast cancers in the TMA were diagnosed in 1995, followed through 2006, and linked to SEER's main database.

RESULTS

The TMA included 354 cases, representing 51% of 687 breast cancers in the HTR (1995). The HTR and TMA cases were similar with respect to patient demographics and tumor characteristics. Seventy-six percent (76%, 268 of 354) of TMA cases were HER2+ and/or ER+, i.e., 28 HER2+ER-, 12 HER2+ER+, and 228 HER2-ER+. There were 67 HER2-ER- cases and 19 were unclassified. Age distributions at diagnosis were bimodal with dominant early-onset modes for HER2+ER- tumors and dominant late-onset modes for HER2-ER+ breast cancers. Epidemiologic patterns for concordant HER2+ER+ (double-positive) and HER2-ER- (double-negative) were intermediate to discordant HER2+ER- and HER2-ER+.

CONCLUSION

Results showed contrasting incidence patterns for HER2+ (HER2+ER-) and ER+ (HER2-ER+) breast cancers, diagnosed in 1995. Though sample sizes were small, this demonstration project validates the potential utility of the RTR for supplementing the SEER program.

Age interacts with the expression of steroid and HER-2 receptors in operable invasive breast cancer

BACKGROUND

The negative association between the oestrogen receptor (ER) and the human epidermal growth factor receptor 2 (HER-2) in breast cancer travels in both directions. ER+ tumours are less likely HER-2+ and HER-2+ tumours are less likely ER+.

METHODS

We studied the age-related immunohistochemical (IHC) expression of ER, progesterone receptor (PR) and HER-2 in 2,227 tumours using age as a continuous variable. Steroid receptors were considered positive for any nuclear staining of invasive cancer cells and for HER-2, either for strong expression by IHC (score 3+) or gene amplification by fluorescence in situ hybridisation (FISH). Based on nonparametric regression, the age-related association between steroid receptors and HER-2 was presented as likelihood curves.

RESULTS

The association between ER or PR and HER-2 is age-related. The age-related expression of ER and PR is HER-2 dependent. In HER-2(-) cases, the odds ratio (OR) for being ER+ was 2.594 (95% CI = 1.874-3.591) up to age 50 and age-independent thereafter; for PR-expression the OR was 2.687 (95% CI = 1.780-4.057) up to age 45 and 0.847 (95% CI = 0.761-0.942) thereafter. In HER-2+ cases, the OR was 0.806 (95% CI = 0.656-0.991) to be ER+ and 0.722 (95% CI = 0.589-0.886) to be PR+. The age-related OR for breast cancers to be HER-2+ is steroid receptor dependent. Taking together, ER+PR+HER-2+ breast cancers appear on average 5.4 years earlier than breast cancers of any other ER/PR/HER-2 phenotype (95% CI = 3.3-7.5; P < 0.0001).

CONCLUSION

There is a qualitative interaction between age and expression of steroid and HER-2 receptors. Our findings suggest a strong age-related selective growth advantage for breast tumour cells belonging to the ER+PR+HER-2+ subgroup.

Evaluation of the prognostic value of HER-2 and VEGF in breast cancer patients participating in a randomized study with dose–dense sequential adjuvant chemotherapy

PURPOSE

To assess the prognostic and predictive significance of HER-2 overexpression and high expression of VEGF in high-risk patients with breast cancer treated with dose-dense sequential chemotherapy.

PATIENTS AND METHODS

From June 1997 until November 2000, 595 patients were randomized to three cycles of epirubicin (E) 110 mg/m2 followed by three cycles of paclitaxel (T) 250 mg/m2 followed by three cycles of "intensified" CMF (cyclophosphamide 840 mg/m2, methotrexate 47 mg/m2 and fluorouracil 840 mg/m2) or to four cycles of E, followed by four cycles of CMF. HER-2 was assessed by immunohistochemistry (IHC) in 394 patients, and by fluorescence in situ hybridization (FISH) in cases scored as 2+ by IHC. VEGF was evaluated in 323 patients by IHC.

RESULTS

HER-2 overexpression was detected in 123 patients (31%) and high expression of VEGF in 233 (72%). The rate of HER-2 overexpression was significantly higher in patients with positive VEGF staining (35% vs. 21%, p=0.02). Overexpression of HER-2 was significantly associated with negative hormonal status, high histologic grade and larger tumors. HER-2 overexpression was a significant negative predictor of DFS (p=0.002), but not of OS. Adjusting for HER-2 overexpression, DFS and OS did not significantly differ between treatment groups. Positive VEGF staining was not associated with receptor status, number of positive nodes, grade, tumor size, incidence of relapse or death.

CONCLUSIONS

For both treatments, HER-2 overexpression was a significant negative prognostic factor for DFS but not for OS, while high expression of VEGF was not significantly associated to either DFS or OS. No predictive ability of HER-2 status or VEGF overexpression for T treatment was evident.

Can molecular markers predict when to implement treatment with aromatase inhibitors in invasive breast cancer?

PURPOSE

Resistance to tamoxifen is linked to overexpression of HER2, and aromatase inhibitors show particular benefit in progesterone receptor (PR)-negative patients. We previously reported reduced survival in patients overexpressing HER1, HER2, and HER3. We now show that both HER1-3 and PR status predicts for early relapse in estrogen receptor (ER)-positive tamoxifen-treated breast cancer patients.

EXPERIMENTAL DESIGN

Tissue microarray technology was used to analyze 402 ER-positive tamoxifen-treated patients. Immunohistochemistry using epidermal growth factor receptor, HER2, HER3, HER4, and PR antibodies was done. Kaplan-Meier life table and Cox Regression analysis (log-rank testing of differences in breast cancer-related relapse on tamoxifen) was done.

RESULTS

HER1-3 (but not HER4) overexpression predicted for early relapse on tamoxifen (P = 0.0060). PR-negative cases were also significantly more likely to relapse while on tamoxifen (P= 0.017). HER1-3-positive and/or PR-negative patients combined as a "high-risk" group were significantly more likely to relapse on tamoxifen in univariate (P < 0.0001) and Cox's multivariate analysis (P = 0.0069). However, this applied to early relapse on tamoxifen only, as any disease relapse after 3 years of tamoxifen was unrelated to PR/HER status.

CONCLUSIONS

We show that HER1-3 and PR status can identify time-dependent de novo tamoxifen resistance with risk declining markedly after 3 years of tamoxifen treatment. These results parallel data from the ATAC and Intergroup Exemastane Study trials which suggest that whereas PR-negative patients derive greater benefit from initial aromatase inhibitor treatment, PR status has no effect on response when given as delayed treatment to those disease free on tamoxifen after 3 years.

Association between tumour characteristics and HER-2/neu by immunohistochemistry in 1362 women with primary operable breast cancer

AIMS

To investigate the association between tumour characteristics and HER-2/neu by immunohistochemistry in primary operable breast cancer.

METHODS

The association between HER-2/neu and other clinicopathological factors was evaluated in 1362 consecutive patients with primary breast cancer treated between 2000 and July 2003 in one centre. Microscopic tumour size, tumour grade, lymph node status, patient's age, oestrogen receptor (ER), progesterone receptor (PR), and joint ER/PR status were evaluated, using the chi2 test for univariate analysis and logistic regression for multivariate analysis. The hormone receptors and HER-2/neu were studied immunohistochemically. Using the HER-2/neu DAKO scoring system, scores of 0, 1+, or 2+ were defined as negative and 3+ as positive. Data for DAKO scores 2+/3+ versus 0/1+ are also presented.

RESULTS

Hormone receptor negative breast cancers were more often HER-2/neu positive than hormone receptor positive cancers, both for ER (28.7% v 6.8%) and PR (19.9% v 5.9%). In multivariate analysis, both ER, PR, and tumour grade were independently associated with HER-2/neu. In ER+ tumours, HER-2/neu overexpression was significantly lower in PR+ than in PR- cases (11.5% v 5.4%). HER-2/neu overexpression (2.7%) was lowest in the large subgroup of ER+PR+ tumours with low tumour grade (grade 1-2), comprising 46.1% of all patients.

CONCLUSIONS

ER, PR, and tumour grade are independent predictors for HER-2/neu overexpression in women with primary operable breast cancer. ER and PR are negatively associated with HER-2/neu, whereas tumour grade is positively associated with HER-2/neu. In women with ER+ tumours, PR status also affects the likelihood of HER-2/neu expression.

Hormone receptors do not predict the HER2/neu status in all age groups of women with an operable breast cancer

BACKGROUND

In breast cancer, there is an inverse relationship between HER2/neu overexpression and receptors for estrogen (ER) or progesterone (PR). Some clinical observations such as the age-related association between hormone receptors and tumour grade, which predicts HER2/neu overexpression, suggest an age-related relationship.

PATIENTS AND METHODS

Our study population consisted of 1362 consecutive women receiving primary surgery for non-metastatic invasive breast cancer. We compared the relationship between both hormone receptors and HER2/neu overexpression in different age groups taking other tumour characteristics into account.

RESULTS

In a multivariate model, considering the overall group, a negative ER, a negative PR and a high tumour grade were predictive for HER2/neu overexpression (P <0.001). Considering 246 women aged < or =45 years, the only predictor for HER2/neu overexpression in this age category was a high tumour grade (P = 0.003). Considering the 1116 women aged >45 years, ER (P = 0.001), PR (P = 0.001) and tumour grade (P <0.001) were associated with HER2/neu (P <0.001).

CONCLUSION

Our findings indicate that the association between ER, PR and HER2/neu overexpression varies with age. The hormone receptors are not an independent predictor for the HER2/neu status in young women while they are in elder patients.

Clinical significance of the quantitative assessment of the cytosolic concentration of HER-2/neu protein in breast cancer by immunoenzymatic assay (ELISA)

PURPOSE

Retrospective analysis to assess the prognostic and predictive value of HER-2/ neu expression in breast tumors, quantified by enzyme immunoassay (ELISA).

METHODS

Quantification of HER-2/neu was performed on cytosolic extracts from 914 cases of primary invasive breast carcinomas. Relapse-free and overall survival data were available from 889 patients. The prognostic value of HER-2/neu levels was assessed considering them as a continuous, dichotomic or quartile variable.

RESULTS

Cytosolic HER-2/neu levels ranged widely in breast carcinomas (median: 746.5 NHU/mg; range: 2.8-80,000 NHU/mg protein). HER-2/neu protein levels were significantly higher in either moderately or poorly differentiated tumors, as well as in those showing a ductal histological type, aneuploidy or a high S-phase fraction. There was a significant and positive association between cytosolic and membranous HER-2/neu levels (n=162, r sub S=0.53; P<0.0001). In addition, cytosolic HER-2/neu level correlated weakly with progesterone receptors but not with estrogen receptors. Elevated cytosolic HER-2/neu levels (> or =1,400 NHU/mg protein) were associated with a high probability of both shortened relapse-free survival and overall survival. This same cut-off value was obtained when we divided the overall group of patients in a training set. However, this HER-2/neu value did not achieve any statistical significance in a validation set used to make sure that the cut-off was correct. Nevertheless, when we divided the obtained data into three different groups with respect to the quartile values (Q) of the intratumoral oncoprotein levels (< or = Q1 vs Q1-Q2 vs > Q3), we observed that patients with either low HER-2/ neu levels (< or = Q1) or high HER-2/neu levels (> Q3) had shorter both relapse-free survival and overall survival curves than those patients with intermediate HER-2/neu levels. On the other hand, high HER-2/neu levels predicted a poor response to adjuvant chemotherapy but not to adjuvant hormonal therapy with tamoxifen.

CONCLUSIONS

The results of the present investigation indicate that by quantitatively determining the content of HER-2/neu oncoprotein, groups of high-risk breast cancer patients could be identified, for a more effective clinical management.

Quantitative association between HER-2/neu and steroid hormone receptors in hormone receptor-positive primary breast cancer

BACKGROUND

HER-2/neu, which encodes a receptor tyrosine kinase, is amplified and overexpressed in 20%-25% of human breast cancers. Such tumors are often resistant to hormone therapy. Despite a general inverse association between HER-2/neu amplification/overexpression and estrogen receptor (ER) and/or progesterone receptor (PR) expression, a fraction of patients are both HER-2/neu- and hormone receptor (HR)-positive. The efficacy of hormone therapy in this group is currently a matter of debate. To better understand the relationship between HER-2/neu positivity and HR expression, we analyzed HER-2/neu, ER, and PR as continuous variables in breast cancer cell lines and two cohorts of primary breast cancer patients.

METHODS

HER-2/neu and ER/PR expression was analyzed by enzyme-linked immunosorbent assay (ELISA) and enzyme immunoassay (EIA), respectively, in 14 human breast cancer cell lines, some of which had been transfected with the HER-2/neu gene. For the clinical study population, HER-2/neu protein levels were assessed by ELISA (cohort A, n = 665), and HER-2/neu gene copy number was determined using fluorescence in situ hybridization (cohort B, n = 894). ER/PR expression was analyzed by EIA (cohort A) or radioligand binding (cohort B). Associations between HER-2/neu and ER/PR expression were analyzed using Spearman's rho correlation and the chi-square test, and absolute levels were compared using the Mann-Whitney U test. All statistical tests were two-sided.

RESULTS

HR-positive human breast cancer cell lines transfected with the HER-2/neu gene expressed statistically significantly lower levels of ER and PR than parental lines. In the clinical cohorts, levels of HER-2/neu overexpression and gene amplification were inversely correlated with ER/PR levels (Cohort A [n = 112]: for ER, r = -0.34, P<.001; for PR, r = -0.24, P =.010. Cohort B [n = 188]: for ER, r = -0.39, P<.001; for PR, r = -0.26, P<.001). Among patients with HR-positive tumors, HER-2/neu-positive tumors had statistically significantly lower ER/PR levels than HER-2/neu-negative ones (Cohort A: for ER, median = 25 fmol/mg [interquartile range [IQR] = 13-78] versus median = 38.5 fmol/mg [IQR = 17-99] and P =.031; for PR, median = 35 fmol/mg [IQR = 12-119] versus median = 88.5 fmol/mg [IQR = 22-236] and P<.001. Cohort B: for ER, median = 44 fmol/mg [IQR = 13-156] versus median = 92 fmol/mg [IQR = 35-235] and P<.001; for PR, median = 36 fmol/mg [IQR = 13-108] versus median = 84 fmol/mg [IQR = 24-250] and P<.001). Patients with higher levels of HER-2/neu overexpression or amplification had statistically significantly lower levels of ER/PR than patients with lower levels of HER-2/neu overexpression or amplification.

CONCLUSION

Because absolute HR levels are strongly related to response to hormone therapy in primary and advanced breast cancer, reduced ER/PR expression may be one mechanism to explain the relative resistance of HER-2/neu-positive:HR-positive tumors to hormone therapy.

Amplification of Her-2/neu gene in Her-2/neu-overexpressing and -nonexpressing breast carcinomas and their synchronous benign, premalignant, and metastatic lesions detected by FISH in archival material

Amplification of Her-2/neu in breast carcinoma is associated with poor prognosis, short disease-free interval, and short survival time in both node-negative and -positive patients. Little is known about the starting point of amplification of Her-2/neu and how it progresses from benign to malignant breast lesions. We attempted to address these questions by evaluating amplification of Her-2/neu in benign, premalignant, and malignant lesions using fluorescence in situ hybridization (FISH). Twenty-six patients with Her-2/neu-overexpressing invasive ductal carcinomas (as judged by strong immunoreactivity with Her-2/neu antibody) and coexisting lesions of ductal hyperplasia (DH), atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) in the vicinity of the invasive tumor (as judged by review of the hematoxylin and eosin-stained sections), as well as metastatic carcinoma in axillary lymph nodes (mets) were selected for this study. In the primary carcinomas, a close relationship was present between overexpression as detected by immunohistochemistry (IHC) and amplification as demonstrated by FISH (85% concordance). Among these patients, amplification of Her-2/neu in ADH was demonstrated in 7 of 13 cases with ADH, and in DCIS, in 21 of 22 cases with DCIS. There was no amplification in DH or normal ductal epithelium. Significantly, in all 12 patients with synchronous positive axillary lymph nodes, there was concordant amplification of Her-2/neu in the primary and metastatic carcinoma. Amplification was consistent in multifocal metastases, despite morphological heterogeneity in some patients. Amplification ratios increased from ADH to DCIS to invasive carcinoma (P <.01, ADH versus DCIS; P <.05, DCIS versus invasive cancer), but there was no difference in amplification ratios between primary cancers and synchronous axillary metastases (P >.05). We also evaluated Her-2/neu amplification in 21 patients without Her-2/neu overexpression in their primary carcinomas (as judged by absent immunoreactivity with Her-2/neu antibody). Three showed amplification in both primary and metastatic lesions, with a low amplification ratio (approximately 2). One patient had amplification in the primary tumor but not in an axillary metastasis. Two patients exhibited slight amplification in the metastatic carcinoma (ratios 1.6 and 2), but not in their primary cancers. This FISH study indicates that amplification of Her-2/neu can emerge de novo in any stage of the disease process, from ADH to metastatic lesions, but most often appears first in ADH or DCIS. The degree of Her-2/neu amplification increases with progression to invasive carcinoma, there being no further increase in synchronous metastasis. Our data suggest that amplification of Her-2/neu appears to be mainly involved in initiation of breast oncogenesis and that its role in progression of breast cancers is uncertain.

Relevance of p185 HER-2/neu oncoprotein quantification in human primary breast carcinoma

The c-erbB-2 proto-oncogene encodes a transmembrane protein tyrosine kinase receptor of 185 kDa (p185) and has been associated with several types of human cancers. In human breast cancer, overexpression of p185 occurs in 15-30% of cases, correlates with poor prognostic factors and characterizes breast cancers with a more aggressive behavior. Overexpression of p185 is usually associated with c-erbB-2 amplification, though it may occur independently and thus define subpopulations of breast cancers which might be of clinical interest. p185 expression is usually detected by immunohistochemistry (IHC) and few studies have been carried out to evaluate the p185 content of breast cancers with an ELISA technique. In this context, we showed, in 106 breast cancer samples, that p185 was expressed at high levels in 13.2%, intermediate levels in 55.7% and negative ones in 31.1% of cases. All p185 positive samples showed a c-erbB-2 oncogene amplification while none of the p185 negative samples and only 4% of p185 imtermediate samples had an amplification of c-erbB-2. p185 expression is significantly correlated with the negativity of estrogen and progestrone receptors, with high levels of cathepsin D and in some conditions with axillary nodal involvement. Thus, using the p185 ELISA assay, the c-erbB-2 status of breast cancers can be defined and moreover a subset can be discriminated which is characterized by intermediate levels of p185 and absence of c-erbB-2 amplification. The quantitative approach towards p185 in breast cancers affords the possibility of identifying more appropriately patients with high or low risk and thus permits adaptation of therapeutic regimens.

Quantitative analysis of p185(HER-2/neu) protein in breast cancer and its association with other prognostic factors

The total cellular p185(HER-2/neu) protein (p185) content was measured by ELISA in 346 invasive primary breast cancers, and the results were compared with those of estrogen (ER) and progesterone (PR) receptors, pS2 and Cathepsin D (Cat D) content. At a cut-off level of 260 fmol/mg protein, 53 of the 346 tumors (15%) were p185-positive. A significant positive correlation was observed between p185 levels and those of Cat D, and a weaker, though significant, positive correlation with ER, and pS2 levels, but not with those of PR. However, when only the 293 p185-negative tumors were considered, the correlation between p185 and ER improved substantially, and statistical significance was reached for PR. p185-positive tumors exhibited lower ER and PR content and higher Cat D content than p185-negative tumors. The pS2 content, in contrast, did not undergo significant variation. Tumors considered to be p185-positive were significantly more frequently positive for Cat D at the cut-off of 45 pmol/mg protein, and were more frequently negative for ER and/or PR, but only significant at the cut-off of 15 fmol/mg or higher for both steroid receptors. Finally, p185 status was not associated with menopausal status, tumor size, axillary-lymph-node invasiveness or distant metastases. These results suggest that 260 fmol/mg protein as the cut-off for p185 allows the identification of a tumoral sub-population with a more aggresive phenotype.

Variations in c-erbB-2 proto-oncogene status in breast cancer tumors as detected by two different cDNA probes

We examined 232 breast carcinomas for c-erbB-2 amplification by Southern analysis using two different cDNA probes. Using these same probes, 95 of these tumors were also examined for mRNA expression by Northern analysis. Amplification was detected in 20 and 17% of the tumors with the probes pHER 2 and pCER 204, respectively, but only 10% showed amplification with both probes. A significantly higher incidence (p < 0.01) of mRNA overexpression was detected with the pHER 2 probe (34%) compared with the pCER 204 probe (16%), with only 11% of tumors demonstrating overexpression with both probes. A total of 10 tumors (11%) exhibited amplification as well as overexpression with pHER 2, whereas significantly fewer (3%) manifested both abnormalities with the larger pCER 204 probe (p < 0.05). Amplification of c-erbB-2, as detected with the pHER 2 probe but not with the pCER 204 probe, was significantly associated with the absence of both estrogen and progesterone receptors (p < 0.05 and p < 0.01, respectively). No relationship was found with other clinical prognostic indicators, such as nodal involvement and metastases. As determined by either probe, overexpression was not associated with prognostic indicators. There was no significant difference in the c-erbB-2 status of tumors from different racial groups.