Chromosome 17 polysomy: correlation with histological parameters and HER2NEU gene amplification

Targeting MET Amplification: Opportunities and Obstacles in Therapeutic Approaches

The MET gene plays a vital role in cellular proliferation, earning it recognition as a principal oncogene. Therapies that target MET amplification have demonstrated promising results both in preclinical models and in specific clinical cases. A significant obstacle to these therapies is the ability to distinguish between focal amplification and polysomy, a task for which simple MET copy number measurement proves insufficient. To effectively differentiate between the two, it is crucial to utilize comparative measures, including in situ hybridization (ISH) with the centromere or next generation sequencing (NGS) with adjacent genes. Despite the promising potential of MET amplification treatment, the judicious selection of patients is paramount to maximize therapeutic efficacy. The effectiveness of MET inhibitors can fluctuate depending on the extent of MET amplification. Future research must seek to establish the ideal threshold value for MET amplification, identify the most efficacious combination therapies, and innovate new targeted treatments for patients exhibiting MET amplification.

Impact of chromosome 17 centromere copy number increase on patient survival and human epidermal growth factor receptor 2 expression in gastric adenocarcinoma

The accurate evaluation of human epidermal growth factor receptor 2 (HER2) status is essential for the appropriate use of targeted therapies. An increased number of chromosome 17 centromere enumeration probe (CEP17) signals may underrate fluorescence in situ hybridization (FISH) outcomes, resulting in false-negative or a false-equivocal HER2 status assessment. The aim of the present study was to assess the frequency of CEP17 copy number increase (CNI), its effects on HER2 protein expression (and the subsequent effects on tumor cells), and the survival outcomes of patients with gastric cancer. Archival primary tumor samples from 244 patients that underwent gastric resection for adenocarcinoma were retrieved for both HER2 protein expression analysis (using immunochemistry) and HER2 gene amplification (using FISH). The associations between HER2 status, CEP17 CNI and multiple clinicopathological parameters (including survival outcome), were assessed. The relationship between CEP17 CNI and HER2 protein upregulation was also investigated. CEP17 CNI was detected in 17.2% of cases, and a strong association between CEP17 CNI and HER2 upregulation was revealed. The impact of CEP17 CNI on survival did not reach statistical significance. Consequently, CEP17 CNI was discovered to be strongly associated with HER2 upregulation in tumor cells, which may characterize a critical issue in HER2 testing. Therefore, the eligibility for HER2-targeted agents in CEP17 CNI-positive patients warrants further recognition.

Centromere 17 copy number gain reflects chromosomal instability in breast cancer

Chromosomal instability (CIN) is known to be associated with prognosis and treatment response in breast cancer. This study was conducted to determine whether copy number gain of centromere 17 (CEP17) reflects CIN, and to evaluate the prognostic and predictive value of CIN in breast cancer. CIN status was determined by summing copy number gains of four centromeric probes (CEP1, CEP8, CEP11, and CEP16) based on fluorescence in situ hybridization and CIN scores were calculated using next generation sequencing data. High CIN was associated with adverse clinicopatholgical parameters of breast cancer. Among them, positive HER2 status, high Ki-67 index and CEP17 copy number gain were found to be independent predictors of high CIN. High CIN was associated with poor clinical outcome of the patients in the whole group, as well as in luminal/HER2-negative and HER2-positive subtypes. CEP17 copy number was significantly higher in the high-CIN-score group than in the low-CIN-score group. A positive linear correlation between the mean CEP17 copy number and the CIN score was found. In conclusion, CEP17 copy number was confirmed as a useful predictor for CIN in breast cancer, and high CIN was revealed as an indicator of poor prognosis in breast cancer.

HER2 status in breast cancer: changes in guidelines and complicating factors for interpretation

Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification is found in about 20% of invasive breast cancers. It is a sole predictive marker for treatment benefits from HER2 targeted therapy and thus, HER2 testing is a routine practice for newly diagnosed breast cancer in pathology. Currently, HER2 immunohistochemistry (IHC) is used for a screening test, and in situ hybridization is used as a confirmation test for HER2 IHC equivocal cases. Since the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines on HER2 testing was first released in 2007, it has been updated to provide clear instructions for HER2 testing and accurate determination of HER2 status in breast cancer. During HER2 interpretation, some pitfalls such as intratumoral HER2 heterogeneity and increase in chromosome enumeration probe 17 signals may lead to inaccurate assessment of HER2 status. Moreover, HER2 status can be altered after neoadjuvant chemotherapy or during metastatic progression, due to biologic or methodologic issues. This review addresses recent updates of ASCO/CAP guidelines and factors complicating in the interpretation of HER2 status in breast cancers.

Retrospective analysis of the association between human epidermal growth factor receptor 2 amplification and chromosome enumeration probe 17 status in patients with breast cancer

The aim of the present study was to identify potential human epidermal growth factor receptor 2 (HER2) amplification, according to American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) 2013 HER2 testing guidelines, in patients previously determined not to possess HER2 amplification, in accordance with previous 2007 guidelines. Potential discrepancies may arise from chromosome enumeration probe 17 (CEP17) amplification, deletion, polysomyor monosomy. HER2, CEP17, tumor protein p53 (TP53) and retinoic acid receptor α (RARA) genes from 67 patient specimens with suspected amplification, polysomy or monosomy of CEP17 were analyzed using fluorescence in situ hybridization. HER2 status was interpreted using 2007 and 2013 ASCO HER2 test guidelines as well as the reference genes TP53 and RARA. According to ASCO/CAP2007 HER2 guidelines, 20 patients exhibited HER2 amplification (29.85%), 41 were without HER2 amplification (including 25 with polysomy, 15 with monosomy and 1 with suspected monosomy plus co-amplification of HER2 and CEP17) and the remaining 6 patients were equivocal. Using ASCO/CAP 2013 HER2 guidelines, 49 patients exhibited HER2 gene amplification (73.1%). The 29-patient increase included 6 originally at equivocal levels but now demonstrating amplification, 22 originally with polysomy but now revealing co-amplification, and 1 with suspected monosomy plus co-amplification of HER2 and CEP17. According to TP53 and RARA, HER2 was amplified in 43 patients (64.1%). Using the revised guidelines, HER2, originally identified as amplified in 6 patients, was not amplified following the introduction of TP53 and RARA control genes. Among these 6, 4 possessed normal TP53 and RARA. The incidence of co-amplification of HER2 and CEP17 was 1.4% (21/1,518). RARA and TP53 are suitable control genes to evaluate HER2 status.

Prognostic significance of centromere 17 copy number gain in breast cancer depends on breast cancer subtype

Increased copy number of chromosome enumeration probe (CEP) targeting centromere 17 is frequently encountered during HER2 in situ hybridization (ISH) in breast cancer. The aim of this study was to clarify the clinicopathologic significance of CEP17 copy number gain in a relatively large series of breast cancer patients. We analyzed 945 cases of invasive breast cancers whose HER2 fluorescence ISH reports were available from 2004 to 2011 at a single institution and evaluated the association of CEP17 copy number gain with clinicopathologic features of tumors and patient survival. We detected 186 (19.7%) cases of CEP17 copy number gain (CEP17≥3.0) among 945 invasive breast cancers. In survival analysis, CEP17 copy number gain was not associated with disease-free survival of the patients in the whole group. Nonetheless, it was found to be an independent adverse prognostic factor in the HER2-negative group but not in the HER2-positive group. In further subgroup analyses, CEP17 copy number gain was revealed as an independent poor prognostic factor in HER2-negative and hormone receptor-positive breast cancers, and it was associated with aggressive histologic variables including high T stage, high histologic grade, lymphovascular invasion, p53 overexpression, and high Ki-67 proliferative index. In conclusion, we found that elevated CEP17 count can serve as a prognostic marker in luminal/HER2-negative subtype of invasive breast cancer. We advocate the use of the dual-colored fluorescence ISH using CEP17 rather than the single-colored one because it gives additional valuable information on CEP17 copy number alterations.

HER2 FISH classification of equivocal HER2 IHC breast cancers with use of the 2013 ASCO/CAP practice guideline

The status of human epidermal growth factor receptor 2 (HER2, ERBB2) determines the eligibility of breast cancer patients to receive HER2-targeted therapy. The majority of HER2 testing in the U.S. is performed using a combination of immunohistochemistry (IHC) screening followed by fluorescence in situ hybridization (FISH) for IHC equivocal cases. In 2013, the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) updated the guideline for HER2 testing. This study evaluates the impact of the 2013 ASCO/CAP updated guideline on final HER2 FISH classification of breast cancers with an equivocal IHC result. For each case, we reported a FISH result according to the 2013 updated guideline and recorded a separated result using the 2007 guideline for investigational purpose. McNemar's test and Bowker's symmetry test were used to compare the classifications by the two guidelines. Among 172 HER2 IHC 2+ equivocal cases, use of the 2103 guideline changed classifications in 36 cases (21 %) when compared with the results expected by use of the 2007 guideline, and yielded a higher proportion of positive (28.5 vs. 23.3 %) and equivocal (16.3 vs. 4.1 %), and a lower proportion of negative (55.2 vs. 72.7 %) cases (p < 0.001). The major classification change with use of the updated guideline is from the HER2 FISH negative to equivocal in 26 cases (15 %). Our study has shown that implementation of the 2013 ASCO/CAP updated guideline has significant impact on HER2 classification for breast cancers with an equivocal HER2 IHC result and therefore increased the use of HER2-targeted therapy. Our data have also shown that reflex FISH is effective for final classification of the IHC equivocal cases and that polysomy 17 (CEP17 copy number ≥3/cell) is present in a significantly higher proportion of cases with an equivocal HER2 FISH classification.

Clinical role of HER2 gene amplification and chromosome 17: a study on 154 IHC-equivocal cases of invasive breast carcinoma patients

Accurate evaluation of human epidermal growth factor receptor 2 (HER2) status is quite crucial for invasive breast tumor patients in order to select anti-HER2 therapy for effective clinical outcomes. Immunohistochemistry (IHC) assay is routinely used to evaluate the HER2 oncoprotein overexpression but is unable to explain the chromosomal and genetic alterations and has been considered as a hot issue in IHC-equivocal cases. We investigated these molecular aberrations in correlation with prognostic factors. A cohort of 154 IHC-equivocal (+2) cases was selected and retrospectively analyzed by dual-probe fluorescence in situ hybridization (FISH) assay by using locus-specific HER2 and centromere enumeration probes (CEP17) for the identification of HER2 proto-oncogene amplification and chromosomal copy number per cell, respectively. The data were analyzed by SPSS 16.0 version using chi-square test (p < 0.05). We identified 36 out of 154 cases (23.4 %) showing HER2 gene amplification (average HER2 gene copies per cell >4 or <4 with HER2/CEP17 ratio >2) in concordance with HER2 oncoprotein overexpression, and significant correlation was observed with prognostic parameters including histological type, tumor grade II to III, histology and pathological type, lymphatic invasion, ductal carcinoma in situ (DCIS), and estrogen-positive and progesterone-negative receptors. Of the 154 cases, 18 cases (11.7 %) showed polysomy 17 with CEP17 probe signals per cell ≥3 and 22 cases (14.3 %) presented monosomy 17 (CEP17 probe signals per cell ≤1). Our data indicate that the use of anti-HER2 therapy should not be suggested unless true evaluation of HER2 protein expression is made regarding gene amplification essentially in IHC-ambiguous invasive breast tumors.

HER2 in solid tumors: more than 10 years under the microscope; where are we now?

HER2 is a well-recognized mediator of the cancerogenic process. It is dysregulated in a wide range of solid tumors, mainly via protein overexpression and/or gene amplification, thus making HER2 an attractive target for tailored treatment. The anti-HER2 therapy trastuzumab was approved for the treatment of HER2-positive metastatic breast cancer patients more than 10 years ago. Since then, trastuzumab and other HER2-inhibitors have been entered into clinical practice for the treatment of breast cancer and, more recently, have been approved to treat HER2-positive metastatic gastric cancers. Currently, HER2-targeted therapies are under evaluation in other tumor types. Due to the relevance of proper patient selection, the accurate assessment of HER2 status is fundamental. This review will discuss the established knowledge and novel insights into the HER2 story, mainly focusing on breast, gastric and colorectal cancers, as well as providing a brief overview of salivary gland, bladder, ovarian and lung tumors.