overexpression is a mechanism of trastuzumab resistance in HER2+ breast cancer patients

Cyclin E amplification/ overexpression is a mechanism of trastuzumab resistance in HER2+ breast cancer patients Scaltriti M, Eichhorn PJ, Cortés J, et al (Vall d'Hebron Inst of Oncology, Barcelona, Spain; et al) Proc Natl Acad Sci U S A 108:3761-3766, 2011

Clinical benefits from trastuzumab and other anti-HER2 therapies in patients with HER2 amplified breast cancer remain limited by primary or acquired resistance. To identify potential mechanisms of resistance, we established trastuzumab-resistant HER2 amplified breast cancer cells by chronic exposure to trastuzumab treatment. Genomewide copy-number variation analyses of the resistant cells compared with parental cells revealed a focal amplification of genomic DNA containing the cyclin E gene. In a cohort of 34 HER2+ patients treated with trastuzumab-based therapy, we found that cyclin E amplification/ overexpression was associated with a worse clinical benefit (33.3% compared with 87.5%, P < 0.02) and a lower progression-free survival (6 mo vs. 14 mo, P < 0.002) compared with nonoverexpressing cyclin E tumors. To dissect the potential role of cyclin E in trastuzumab resistance, we studied the effects of cyclin E overexpression and cyclin E suppression. Cyclin E overexpression resulted in resistance to trastuzumab both in vitro and in vivo. Inhibition of cyclin E activity in cyclin E-amplified trastuzumab resistant clones, either by knockdown of cyclin E expression or treatment with cyclindependent kinase 2 (CDK2) inhibitors, led to a dramatic decrease in proliferation and enhanced apoptosis. In vivo, CDK2 inhibition significantly reduced tumor growth of trastuzumab-resistant xenografts. Our findings point to a causative role for cyclin E overexpression and the consequent increase in CDK2 activity

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in trastuzumab resistance and suggest that treatment with CDK2 inhibitors may be a valid strategy in patients with breast tumors with HER2 and cyclin E coamplification/over-expression. Previous studies have demonstrated that high cyclin E expression is a poor prognostic factor in breast cancer.1 Our group recently published data that demonstrated both a prognostic and a predictive role for cyclin E in human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer.2 Briefly, in a population of 117 patients with HER2-overexpressing tumors treated in an era prior to the use of adjuvant trastuzumab, we demonstrated that disease-specific survival could be stratified based on levels of cyclin E expression. In the laboratory, we then showed that expression of cyclin E, particularly the more tumorigenic low-molecularweight isoforms, decreases upon HER2 downregulation using small interfering RNA or HER2 inhibition with trastuzumab. Importantly, we also showed synergistic activity of trastuzumab and the CDK inhibitor roscovitine in tumors overexpressing both HER2 and cyclin E. Cyclin E depends on binding to CDK2 to mediate its effects on cell cycle progression; the CDK inhibitor roscovitine, therefore, functions as cyclin Eetargeted therapy. In this study by Scaltriti and colleagues, they follow up on our initial observation of crosstalk between HER2 and cyclin E and suggest that cyclin E could also prove to be a factor predictive of poor response to trastuzumab therapy. These investigators generated a trastuzumab-resistant, HER2-overexpressing breast cancer cell line (BT474R) and performed in vitro and in vivo experiments that demonstrated that cyclin E overexpression accounted for the resistance phenotype. Importantly, their findings were consistent with the clinical

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observation that patients with tumors overexpressing both HER2 and cyclin E derived less benefit from treatment with trastuzumab than those with low cyclin E expression. These findings require prospective validation in a larger cohort of patients. Both studies add to a growing body of literature that describes the interaction between HER2 and cyclin E in breast cancer and provide additional data regarding mechanisms of resistance to trastuzumab therapy. Trastuzumab improves survival for patients with HER2-overexpressing breast cancer in both the metastatic and adjuvant settings; however, there remains a population of patients who either have primary resistance to trastuzumab-based therapy or acquire resistance after an initial response. The study by Scaltriti and colleagues, as well as our study, demonstrates that such resistant tumors that overexpress both cyclin E and HER2 are sensitive to CDK2 inhibition in vitro and in vivo. This suggests that there is a potential therapeutic agent for use in these patients and further investigation of this in a clinical trial is warranted. The relationship between cyclin E overexpression and trastuzumab resistance proposed by both studies needs further validation in the clinical setting. These data suggest a role for the routine assessment of HER2overexpressing tumors for the concomitant overexpression of cyclin E. When tumors overexpressing both of these proteins are identified, novel strategies targeting HER2- and cyclin Eassociated kinase activity may be warranted. E. A. Mittendorf, MD K. Keyomarsi, PhD K. K. Hunt, MD

References 1. Keyomarsi K, Tucker SL, Buchholz TA, et al. Cyclin E and

survival in patients with breast cancer. N Engl J Med. 2002;347:1566-1575. 2. Mittendorf EA, Liu Y, Tucker SL, et al. A novel interaction between

HER2/neu and cyclin E in breast cancer. Oncogene. 2010;29: 3896-3907.

DIAGNOSTIC IMAGING Axillary Ultrasound and FineNeedle Aspiration in the Preoperative Evaluation of the Breast Cancer Patient: An Algorithm Based on Tumor Size and Lymph Node Appearance Mainiero MB, Cinelli CM, Koelliker SL, et al (The Warren Alpert Med School of Brown Univ, Providence, RI; The Johns Hopkins Hosp, Baltimore, MD; et al) AJR Am J Roentgenol 195:1261-1267, 2010

Objective.dThe objective of our study was to evaluate the utility of ultrasound-guided fine-needle aspiration (FNA) of the axillary lymph nodes in breast cancer patients depending on the size of the primary tumor and the appearance of the lymph nodes. Subjects and Methods.dData were collected about tumor size, lymph node appearance, and the results of ultrasound-guided FNA and axillary surgery of 224 patients with breast cancer undergoing 226 ultrasound-guided FNA. Lymph nodes were classified as benign if the cortex was even and measured <3 mm, indeterminate if the cortex was even but measured $3 mm or measured <3 mm but was focally thickened, and suspicious if the cortex was focally thickened and measured $3 mm or the fatty hilum was absent. The results of ultrasound-guided FNAs were analyzed by the sonographic appearance of the axil-

lary lymph nodes and by the size of the primary tumor. The sensitivity and specificity of ultrasound-guided FNA were calculated with axillary surgery as the reference standard. The sensitivity and specificity of axillary ultrasound to predict the ultrasound-guided FNA result were calculated. Results.dOf the 224 patients, 51 patients (23%) had a positive ultrasound-guided FNA result, which yields an overall sensitivity of 59% and specificity of 100%. The sensitivity of ultrasound-guided FNA was 29% in patients with primary tumors #1 cm, 50% in patients with tumors >1 to #2 cm, 69% in patients with tumors >2 to #5 cm, and 100% in patients with tumors >5 cm. The sensitivity of ultrasound-guided FNA in patients with normal-appearing lymph nodes was 11%; indeterminate lymph nodes, 44%; and suspicious lymph nodes, 93%. Sonographic characterization of lymph nodes as suspicious or indeterminate was 94% sensitive and 72% specific in predicting positive findings at ultrasound-guided FNA. Conclusion.dUltrasound-guided FNA of the axillary lymph nodes is most useful in the preoperative assessment of patients with large tumors (>2 cm) or lymph nodes that appear abnormal. In this article by Mainiero and colleagues, the authors evaluated the utility of ultrasound-guided axillary lymph node FNA in patients with breast cancer

according to the size of the primary breast cancers and the sonographic appearance of the axillary lymph nodes. In this study, 226 ultrasound-guided FNAs were performed in 222 women and 2 men. The authors showed that ultrasound-guided axillary lymph node FNA was most useful in the preoperative assessment of patients with large tumors (>2 cm) and/or axillary lymph nodes that appeared abnormal on sonography. In recent years, the use of sonography to evaluate the axillary lymph node basins of patients with known or suspected breast cancer has increased. Axillary sonography has been coupled with ultrasound-guided axillary lymph node FNA in practices with strong cytology support1 and ultrasound-guided axillary lymph node core biopsy in practices without good cytology support. If ultrasound-guided axillary lymph node biopsy is negative for metastatic disease, the patient then undergoes sentinel lymph node biopsy. A positive ultrasound-guided axillary lymph node biopsy obviates sentinel lymph node biopsy, and the patient then undergoes axillary lymph node dissection. At several institutions, patients with metastatic disease proven by axillary lymph node biopsy are treated with neoadjuvant chemotherapy prior to axillary lymph node dissection. In this prospective study, patients with newly diagnosed breast cancer who were considered to be candidates

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