Abstract P6-17-09: Event-free survival by ADCC status from a follow-up study comparing SB3 (trastuzumab biosimilar) with reference trastuzumab for HER2 positive breast cancer in neoadjuvant setting

Background: SB3 has been approved by the European Commission as a biosimilar of reference trastuzumab (TRZ). Equivalent breast pathologic complete response (bpCR) rate and comparable event-free survival (EFS) and overall survival between SB3 and TRZ have been reported.1-3 Upon monitoring quality attributes of TRZ for the development of SB3, a marked downward shift in antibody-dependent cell-mediated cytotoxicity activities (ADCC) was observed in TRZ lots with expiry dates from Aug 2018 to Dec 2019.4 Some of these lots were used in this study. The objective of this report is to evaluate event-free survival by ADCC status from an additional one-year follow-up study.

Methods: Patients with HER2 positive early or locally advanced breast cancer were randomly assigned to receive SB3 or TRZ in neoadjuvant setting concurrently with chemotherapy. Patients then underwent surgery followed by adjuvant SB3 or TRZ. After completion of therapy, patients from selected countries participated in a long-term follow-up study. In TRZ, patients exposed to at least one shifted ADCC lot and those not exposed to shifted ADCC lot during neoadjuvant period were considered as “Exposed” and “Unexposed,” respectively. EFS was defined as the time from the date of randomization to the date when the first event occurred. An event was defined as disease recurrence or progression (local, regional, distant or contralateral) or death due to any cause. EFS after additional one-year follow-up was analyzed by ADCC status in the long-term follow-up set (LFS).

Results: A total of 367 patients (SB3, N=186; TRZ, N=181) were included in the LFS. Within TRZ, 55 patients were Unexposed and 126 patients were Exposed. At a median follow-up duration of 30.1 months in SB3 and 30.2 months in TRZ from initiation of study treatment, 4.8% patients in SB3, 3.6% in Unexposed and 10.3% in Exposed experienced events. 4.3% patients in SB3, 1.8% in Unexposed and 9.5% in Exposed experienced recurrence after surgery (Table). Two-year EFS rate was 96.7% in SB3, 98.2% in Unexposed and 92.5% in Exposed.

Conclusion: A significantly higher proportion of patients experienced events in Exposed compared to Unexposed (HR 0.07, 95% CI 0.01-0.58, p-value=0.0137). No significant difference in EFS was found between SB3 and Unexposed. Although this study has a relatively short follow-up and has not been powered to evaluate the impact of ADCC on survival, these results suggest a possible correlation between ADCC and clinical efficacy. Further long-term results will follow.

Summary of Event-free Survival (LFS)  TRZEFS Hazard ratio (95% CI), p-value SB3 N=186All N=181Unexposed N=55Exposed N=126SB3 vs TRZ AllSB3 vs TRZ UnexposedTRZ Unexposed vs TRZ ExposedPatients with event, n (%)9 (4.8%)15 (8.3%)2 (3.6%)13 (10.3%)0.49 (0.21, 1.14) p=0.09751.19 (0.23, 6.18) p=0.83760.07 (0.01, 0.58) p=0.0137Recurrence after surgery8 (4.3%)13 (7.2%)1 (1.8%)12 (9.5%)   Progression before surgery1 (0.5%)1 (0.6%)1 (1.8%)0 (0.0%)   Death0 (0.0%)1 (0.6%)0 (0.0%)1 (0.8%)   

Reference:

1. Pivot X et al. J Clin Oncol. 2018; 36:968-74

2. Pivot X et al. Eur J Cancer. 2018; 93:19-27

3. Pivot X et al. J Clin Oncol. 2018; 36 (suppl; abstr e12631)

4. Kim S et al. MAbs. 2017; 9:704-14

Citation Format: Pegram MD, Pivot X, Cortes J, Curigliano G, Yoon Y, Lim J, Song S, Hong E. Event-free survival by ADCC status from a follow-up study comparing SB3 (trastuzumab biosimilar) with reference trastuzumab for HER2 positive breast cancer in neoadjuvant setting [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-09.

Abstract P6-17-36: Consensus and disagreement among experts for treatment of patients with HER2+ early-stage breast cancer suggests unmet need for online decision support tool

Treatment (tx) choices for HER2+ early stage breast cancer (EBC) have become increasingly complex. Clinicians and patients must decide 1) which chemotherapy and HER2-targeted agents to use, 2) the sequence of surgery and chemotherapy: either neoadjuvant (neoadj) or adjuvant (adj) tx, and 3) whether to shorten or extend maintenance HER2-targeted tx.

As tx options expand, so does the need for online decision aids. One online decision support tool was developed in 2015 to provide specific tx recommendations for pts with EBC and showed that community healthcare providers (HCPs) did not consistently align with experts for neoadj or adj tx of many pts with EBC (SABCS 2015 Abs P5-09-04).

This study includes analysis of neoadj and adj tx practice patterns of 5 breast cancer experts based on their tx recommendations for 270 unique HER2+ EBC case scenarios made for development of a 2018 online decision tool. We aim to compare these recommendations with the intended treatment of clinicians using the tool.

Results

Experts agree on neoadj tx approaches: initial surgery, no neoadj tx for pts with cT1a/b N0 tumors; neoadj tx before surgery for pts with ≥cT2 or N+ tumors. There was disparity among experts for pts with cT1c N0 disease: 3 experts recommend neoadj TCH±P and 2 recommend proceeding directly to surgery.

Experts generally recommend adj TCHP for pts with stage II N+ or higher HER2+ EBC who did not receive neoadj tx. In addition, 5/5 experts would consider extended adj tx with neratinib for these pts if HR+ and 2/5 experts would also consider neratinib if HR–.

In pts who received neoadj chemo+HER2 tx, post-surgery management depends on response to neoadj tx. For pts with pCR, 5/5 experts generally agree on continuing H+P if both were given as neoadj tx or H alone if only H given as neoadj tx for a total of 1 yr of anti-HER2 Ab tx and 2/5 experts would consider extended adj tx with neratinib for HR+ disease. For pts with residual disease, experts would recommend continuing H+P if both were given as neoadj tx and most would add P for subsequent adj tx if H alone was given to complete a total of 1 yr of anti-HER2 Ab tx (Table1). All experts would consider extended adj tx with neratinib for HR+ disease and 3/5 experts would also consider neratinib for HR– disease. None of the experts recommended less than 12 mos of adj HER2-targeted tx.

We will present analyses of cases entered into our online tool and detailed comparisons of expert and the intended treatment of clinicians using the tool.

Conclusions

Practice patterns are changing rapidly and are more complex in response to the evolving treatment landscape for HER2+ EBC. This analysis highlights several areas of expert consensus; however, disparities remain for select cases. The current tool addresses an unmet medical need for expert-led evaluation of HER2+ EBC tx choices and warrants further investigation.

Expert Recommendations: Initial Adj HER2 Ab Tx After Neodj Tx With H Alone ExpertsResponse12345pCR (HR-)HHHHHpCR (HR+)HHHHHypT1a-c N0 (HR-)H + PHH + PH + PH + PypT1a-c N0 (HR+)H + PHHH + PHypT2 N0 (HR-)H + PH + PH + PH + PH + PypT2 N0 (HR+)H + PH + PHH + PH + PypTany N+ (HR+ or HR-)H + PH + PH + PH + PH + P

Citation Format: Holmes FA, Rosenthal KM, Hurvitz S, Pegram MD, Yardley DA, Obholz KL, O'Shaughnessy J. Consensus and disagreement among experts for treatment of patients with HER2+ early-stage breast cancer suggests unmet need for online decision support tool [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-36.

Abstract P6-05-05: Discistronic reporter screen for internal ribosome entry site (IRES) - mediated translational regulation of truncated p110 ERBB2 isoform

Background:

We and others demonstrated that truncated p110 ERBB2 (p110 t-ERBB2, also as 611CTF) is a hyperactive truncated ERBB2 isoform capable of increasing cell migration and invasion in multiple cell types in vitro, and induction of human breast epithelial cell (HMLE) xenograft formation in vivo [Ward, et al., Oncogene (2013) 32, 2463–2474]. p110 t-ERBB2 arises through alternative initiation of translation from methionine 611, however, it is unclear how regulation of its expression may be achieved. mRNA structural elements termed internal ribosome entry sites (IRESs) can initiate translation in a cap-independent manner when canonical cap-dependent translation is severely compromised. By cloning the EGFR 5' untranslated region (UTR) between the Renilla and firefly luciferase open reading frames of pRF, Webb, et al. have reported human EGFR 5' UTR sequence can initiate expression of a downstream open reading frame via an IRES [Oncogenesis (2014) 3, e134]. Therefore, we sought to identify presence of a putative IRES within the 5'UTR ERBB2 mRNA which might mediate alternative ERBB2 protein translation initiation under stress conditions and promote p110 t-ERBB2 biosynthesis.

Methods:

Discistronic reporter pRF was used as the backbone vector to detect IRES activity. Promoter-less vector pRFΔP were constructed by removing SV40 promoter via restriction digestion. The HER2 mRNA 5'UTR (from both variant 1 and variant 3) and several overlapping sequences from full length ERBB2 (p185 ERBB2) start codon to p110 t-ERBB2 start codon were cloned between the Renilla and firefly luciferase open reading frames of pRF and pRFΔP, then the resultant constructswere transiently transfected into different cell lines(BT474, SK-BR3, MCF-7, HeLa, CHO). Three control constructs pRF (empty vector control), pRF-Tub (negative control, containing βtubulin 5'UTR, which lacks IRES activity) and pRF-myc (positive control, containing the well-characterized c-myc IRES) were parallel-transfected. Luciferase expression was then quantified using a Dual Luciferase Assay Kit (Promega, Madison, WI, USA) following manufacturer's instructions. Parallel western blot analysis and qRT-PCR were also conducted.

Results:

In this report, we demonstrate that in BT474 and SK-BR3 cells, no IRES activity was detected within human ERBB2 5'UTR sequences under non-stressed conditions, or under serum-starvation, hypoxic conditions or thapsgargin-induced endoplasmic reticulum stress -- conditions when global translation was compromised.The construct pRF-+265/+1561 (within ERBB2 mRNA coding sequence, 5' to the p110 t-ERBB2 start codon) displayed a 10-21 fold increase in firefly/Renilla activity when compared with the empty control pRF and negative control pRF-Tub,consistent with the possibility that the region between +265/+1561 may contain a cryptic promoter.

Conclusions:

These data are inconsistent with the hypothesis that a 5'UTR IRES-mediated mechanism is involved in the translation of p110 t-ERBB2 isoform, and that other mechanisms are operative in alternative translational regulation/biosynthesis of p110 ERBB2 isoform.

Citation Format: Zong Y, Li Y, Liu X, Pegram MD. Discistronic reporter screen for internal ribosome entry site (IRES) - mediated translational regulation of truncated p110 ERBB2 isoform [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-05-05.

Abstract OT1-02-07: SOPHIA: A phase 3, randomized study of margetuximab plus chemotherapy vs trastuzumab plus chemotherapy in the treatment of patients with HER2+ metastatic breast cancer

Background: Despite significant advances in targeted therapy, HER2+ metastatic breast cancer (MBC) remains incurable. Ideal treatment includes pertuzumab and trastuzumab in combination with a taxane in the first line setting, followed by ado-trastuzumab emtansine on progression. Optimal treatment regimens in the third and greater line of therapy are not defined, but continued anti-HER2 therapy is recommended. Margetuximab is a Fc-modified monoclonal antibody to HER2 that recognizes the same epitope on HER2 as does trastuzumab, with similar affinity. Margetuximab demonstrates increased affinity to the activating CD16A Fc-receptor found on NK cells and macrophages and decreased affinity to the inhibitory CD32B receptor compared to trastuzumab. In vitro studies showed enhanced antibody dependent cell-mediated cytotoxicity compared to trastuzumab. In a Phase 1 dose escalation and expansion trial, margetuximab showed single agent clinical activity against HER2+ tumors in patients previously treated with trastuzumab and other anti-HER2 agents. Methods: SOPHIA is a randomized, prospective study testing the hypothesis that margetuximab plus chemotherapy (CTX) is more effective than trastuzumab plus CTX in patients previously treated for HER2+ MBC. Sequential primary endpoints are centrally assessed progression free survival (PFS) and overall survival (OS). The study size of 530 patients is determined to have 80% power to detect a hazard ratio for OS of 0.75. Secondary endpoints are investigator assessed PFS and centrally assessed overall response rate. Eligibility includes prior treatment with trastuzumab, pertuzumab, and ado-trastuzumab emtansine; no more than 3 prior lines of therapy in the metastatic setting; prior demonstration of HER2+ status at a local reference laboratory; and absence of active brain metastases. Eligible patients are randomized 1:1 to receive CTX (physician's choice: capecitabine, eribulin, gemcitabine or vinorelbine) plus either margetuximab or trastuzumab until disease progression or toxicity. Antibody may be continued after stopping CTX in patients with responding or stable disease. Progress to date: The trial was initiated July 2015 and is ongoing in the US and Europe with planned expansion to Korea and Israel. ClinicalTrials.gov Identifier NCT02492711; Eudract 2015-000380-13.

Citation Format: Rugo HS, Pegram MD, Gradishar WJ, Cortes J, Curigliano G, Hong S, Wigginton JM, Lechleider RJ, Cardoso F. SOPHIA: A phase 3, randomized study of margetuximab plus chemotherapy vs trastuzumab plus chemotherapy in the treatment of patients with HER2+ metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT1-02-07.

Abstract OT3-01-04: An open-label, single-arm, phase II study of pertuzumab with high-dose trastuzumab for the treatment of central nervous system progression post-radiotherapy in patients with HER2-positive metastatic breast cancer (PATRICIA)

Background: Central nervous system (CNS) metastases are observed in up to half of patients with HER2-positive metastatic breast cancer (MBC), with incidence likely to continue to rise due to longer survival through improved systemic treatments. While radiotherapy-based approaches can be effective, there are potential short- and long-term toxicities, and patients frequently progress. CNS response to existing systemic therapies has been generally poor, and there is a high unmet need with no approved treatment for CNS metastases in HER2-positive MBC. Combination of the HER2-targeted monoclonal antibodies trastuzumab and pertuzumab provides a more comprehensive blockade of HER2 than either antibody alone, and data from the phase III CLEOPATRA trial suggest that adding pertuzumab to trastuzumab and docetaxel may delay onset of CNS disease. Trastuzumab concentrations in the CNS are increased under conditions of an impaired blood–brain barrier (BBB) and subtherapeutic levels in the CNS may be related to insufficient dosing rather than inability to cross the BBB. The PATRICIA trial is evaluating the addition of pertuzumab with high-dose trastuzumab to a patient's current systemic treatment for HER2-positive MBC patients with CNS progression post-radiotherapy and stable systemic disease.

Study design: In this US-based, phase II, open-label, single-arm study, patients will receive intravenous pertuzumab (840 mg loading dose followed by 420 mg every 3 weeks) in combination with intravenous high-dose trastuzumab (6 mg/kg weekly) in addition to their current systemic therapy (except for ado-trastuzumab emtansine or lapatinib) until disease progression or unacceptable toxicity.

Eligibility criteria: Patients aged ≥18 years with confirmed HER2-positive MBC with new and/or progressive CNS lesions >60 days after whole-brain radiotherapy or stereotactic radiosurgery for CNS metastases, performance status 0–1, and stable systemic disease will be eligible. Patients must have a baseline left ventricular ejection fraction (LVEF) ≥50%, no significant history of cardiac disease or current use of anthracyclines, life expectancy >12 weeks, and not be pregnant or lactating.

Aims: The primary efficacy endpoint will be objective response rate (ORR) in the CNS, assessed by the investigator using RANO–BM criteria. Secondary endpoints will include duration of CNS response, progression-free survival (CNS and/or non-CNS), overall survival, and safety. Pharmacokinetic and patient-reported outcomes will also be evaluated. LVEF will be assessed throughout treatment and follow-up. An interim analysis will be performed when 15 patients have completed 2 cycles, and the study will be stopped if no clinical benefit (complete response, partial response, or stable disease in the CNS) is seen or if two or more patients have congestive heart failure events related to trastuzumab or pertuzumab.

Statistical methods: The recruitment target is 40 patients; with 35 evaluable, the 95% confidence interval around an estimated ORR of 20% will be 8.4–36.9%. The trial opens for accrual in Q3 2015.

Citation Format: Lin NU, Pegram MD, Lai C, Lacasia A, Stein A, Yoo B, Perez EA. An open-label, single-arm, phase II study of pertuzumab with high-dose trastuzumab for the treatment of central nervous system progression post-radiotherapy in patients with HER2-positive metastatic breast cancer (PATRICIA). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-01-04.

Abstract P6-04-10: Components of cap-independent translation as novel targets in breast cancer

Background: The majority of cellular mRNAs are translated in a cap-dependent manner, involving ribosome assembly at 5’ 7-methylguanylate cap structures followed by scanning and initiation at a favorable AUG codon. Alternatively, mRNA structural elements termed internal ribosome entry sites (IRESs) facilitate translation in a cap-independent manner, and have been identified in mRNAs encoding many canonical cellular oncogenes, including c-MYC, c-SRC, XIAP, Aurora-A kinase, and IGF1R. IRES trans-activating factors (ITAFs) are accessory proteins that augment or inhibit translation mediated by specific IRES sequences, via binding to IRES structures and/ or other translational machinery. In addition, conversion of ribosomal RNA (rRNA) uracil bases to pseudouracil enhances IRES-mediated translation.

Methods: Analysis of publically available microarray datasets of breast cancer and normal breast tissue clinical specimens revealed that expression of several ITAFs is upregulated at the mRNA level in malignant tissues compared to normal controls. mRNAs encoding the ITAFs polypyrimidine tract binding protein 1 (PTBP1), splicing factor proline/ glutamine rich (SFPQ), poly-RC binding protein 2 (PCBP2), and interleukin enhancer binding factor 2 (ILF2, also NF45) were significantly upregulated (p < 0.05), as well as mRNA encoding the dyskeratosis congenita 1 (DKC1) rRNA-modifying enzyme. Independent analysis of an 855 human breast tumor dataset revealed that high mRNA expression of DKC1 and ILF2 are enriched in basal-like breast tumors compared to other intrinsic subtypes (t-test, p<0.01). Kaplan-Meier analyses revealed that high expression of DKC1 or ILF2 mRNAs were both significantly associated with decreased relapse-free survival duration (p = 0.0007 and p = 0.002, respectively).

To investigate the biological impact of ITAF and DKC1 silencing, PTBP1, PCBP2, SFPQ, and DKC1 knockdown was accomplished using pGIPZ and pTRIPZ lentiviral shRNA vectors. Silencing of these genes and concomitant reduction in protein levels (measured by western blot) led to significant proliferation impairment in MDA-MB-231, MDA-MB-436, and MCF7 breast cancer cells in culture, using Alamar Blue assay. In addition, 4T1 mouse mammary carcinoma cells express DKC1, PTBP1 and SFPQ, and may serve as a useful model in immunocompetent mice.

Conclusions and future directions: Future experiments will include investigation of protein-level expression in archival human specimens using immunohistochemistry, as well as investigation of the effects of ITAF/ DKC1 silencing in human xenografts using NOD/ SCID mice. Based on their increased expression in malignant breast tissues and activity in translation of oncoproteins, cellular ITAF genes and DKC1 gene may represent novel therapeutic targets for intervention. In particular, the increased expression of DKC1 enzyme and ILF2 in basal-like breast cancers implies a possible therapeutic opportunity in triple-negative breast cancers.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-10.

Abstract P5-08-03: In vitro resistance to ERBB2-targeted therapies does not bestow cross-resistance to antibody dependent cellular cytotoxicity

Background:

The advent of ERBB2-directed therapies, including trastuzumab and lapatinib, has changed the clinical management of ERBB2+ breast cancer and improved patient outcomes. However, both de novo and acquired resistance to ERBB2-targeting agents remain significant clinical problems; thus, it is important to understand the mechanisms that tumor cells use to resist and/ or escape ERBB2-directed therapeutic agents. A growing body of evidence supports the role of immune effector cells in trastuzumab-induced tumor cell lysis in vivo, which is hypothesized to occur through antibody dependent cellular cytotoxicity (ADCC) mediated by natural killer cells bearing FC gamma receptors. Existing in vitro models of trastuzumab and lapatinib resistance are limited in that they are most often generated by incubating tumor cells with drug alone, outside the context of the host immune system. Consequently, the impact of in vitro generated drug resistance on ADCC susceptibility has not been defined. In this study, we tested existing trastuzumab and lapatinib resistant breast cancer cell lines for ADCC sensitivity.

Materials and Methods:

The ERBB2 amplified breast cancer cell lines BT474 and SKBR3, which are sensitive to trastuzumab-mediated ADCC, were selected for trastuzumab and lapatinib resistance. Drug resistant cells were generated by serial culture in the presence of escalating doses of trastuzumab and/or lapatinib until complete tolerance was acquired at clinically achievable concentrations (100μg/ml trastuzumab and 2.6μM lapatinib). Drug sensitivity was assessed by Alamar Blue assay. Cell resistance to trastuzumab-mediated ADCC was measured by Calcein-AM release assay, using 1μg/ml antibody concentration and four different effector target ratios (20:1, 10:1, 5:1, and 1:1), with a minimum of five replicates. Human peripheral blood lymphocytes freshly isolated from buffy coat were used as effector cells.

Results and Discussion:

Neither BT474 nor SKBR3 cells with acquired resistance to single agent trastuzumab (HerR), lapatinib (LapR), or both in combination (DualR) demonstrated cross-resistance to effector cell-mediated ADCC at any of the E:T ratios tested. At the highest E:T ratio tested (20:1), trastuzumab-induced ADCC of control BT474 cells resulted in 61.92% cell lysis (95% CI = 3.97), compared to 64.97% lysis for BT-HerR cells (95% CI = 2.87, Student's t-test p > 0.1). Similarly, BT-LapR and DualR cell lysis was 58.13% and 63.66%, respectively (95% CI = 2.62 and 6.57, Student's t-test p > 0.1). Additionally, trastuzumab-induced ADCC of control SKBR3 cells resulted in 89.98% cell lysis (95% CI = 4.29), compared to 93.53% lysis for SK-HerR cells (95% CI = 0.81, Student's t-test p > 0.1). SK-LapR and DualR cell lysis was 94.81% and 92.09%, respectively (95% CI = 0.6 and 2.66, Student's t-test p > 0.1). Our results indicate the importance of incorporating immune effector cells to in vitro models of trastuzumab resistance. Accordingly, we have begun modeling ADCC resistance in vitro to further investigate the relationship between targeted antibody therapies, effector cell-mediated cytolysis, and mechanisms of tumor immune escape.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-08-03.

Truncated p110 ERBB2 induces mammary epithelial cell migration, invasion and orthotopic xenograft formation, and is associated with loss of phosphorylated STAT5

Truncated-ERBB2 isoforms (t-ERBB2s), resulting from receptor proteolysis or alternative translation of the ERBB2 mRNA, exist in a subset of human breast tumors. t-ERBB2s lack the receptor extracellular domain targeted by therapeutic anti-ERBB2 antibodies and antibody–drug conjugates, including trastuzumab, trastuzumab-DM1 and pertuzumab. In clinical studies, expression of t-ERBB2 in breast tumors correlates with metastasis as well as trastuzumab resistance. By using a novel immuno-microarray method, we detect a significant t-ERBB2 fraction in 18 of 31 (58%) of immunohistochemistry (IHC)3+ ERBB2+ human tumor specimens, and further show that t-ERBB2 isoforms are phosphorylated in a subset of IHC3+ samples (10 of 31, 32%). We investigated t-ERBB2 biological activity via engineered expression of full-length and truncated ERBB2 isoforms in human mammary epithelial cells (HMECs), including HMEC and MCF10A cells. Expression of p110 t-ERBB2, but not p95m (m=membrane, also 648CTF) or intracellular ERBB2s, significantly enhanced cell migration and invasion in multiple cell types. In addition, only expression of the p110 isoform led to human breast epithelial cell (HMLE) xenograft formation in vivo. Expression of t-ERBB2s did not result in hyperactivation of the phosphoinositide kinase-3/AKT or mitogen-activated protein kinase signaling pathways in these cells; rather, phosphoproteomic array profiling revealed attenuation of phosphorylated signal transducer and activator of transcription 5 (STAT5) in p110-t-ERBB2-expressing cells compared to controls. Short hairpin-mediated silencing of STAT5 phenocopied p110-t-ERBB2-driven cell migration and invasion, while expression of constitutively active STAT5 reversed these effects. Thus, we provide novel evidence that (1) expression of p110 t-ERBB2 is sufficient for full transformation of HMEC, yielding in vivo xenograft formation, and (2) truncated p110 t-ERBB2 expression is associated with decreased phosphorylation of STAT5.

PD01-09: Identifying Novel Mechanisms of Resistance to Lapatinib in ERBB2+ Breast Cancer Cells through Whole Genome Mutational Analysis

Background: Overexpression of the epidermal growth factor receptor ERBB2 (HER2) is found in 20% of human breast cancers. Therapies targeting ERBB2 including trastuzumab and lapatinib have significantly improved the outlook for women with ERBB2+ breast cancer. However, resistance to these agents occurs frequently and remains a significant clinical problem. In the case of lapatinib resistance, the mechanism(s) of resistance remain poorly understood, since the current proposed rationale thought to limit lapatinib's anti-tumor effects has been difficult to reconcile with clinical data. Therefore, we hypothesize that novel mechanisms of resistance could be identified by mapping genomic variations in ERBB2+ cells with acquired resistance to lapatinib. The identification of such mutations may provide insights into mechanisms of resistance and may indicate therapeutic strategies to overcome lapatinib resistance in ERBB2+ breast cancer.

Material and Methods: SKBR3 breast cancer cells resistant to lapatinib were generated through serial passage by exposure of drug sensitive parental SKBR3 cells to increasing concentrations of lapatinib up to the peak plasma concentration observed in human subjects (2.6 uM (SK-lapR)). Multiple signaling pathways in lapatinib sensitive and resistant cells were interrogated by Reverse Phase Protein Array (RPPA) and western blot analysis. To identify genome wide somatic mutations, the Exome of lapatinib resistant and sensitive SKBR3 cells was sequenced utilizing next generation deep sequencing. Following exclusion of germline variants, the acquired gene mutations in lapatinib resistant SKBR3 cells were confirmed by DNA re-sequencing of PCR amplified DNA segments.

Results and Discussion: Analysis of activated signaling pathways in lapatinib resistant and sensitive SKBR3 cells did not confirm any of the previously proposed mechanisms of resistance. In particular, these cells show no activation of AKT or alternative receptor tyrosine kinases such as IGF-IR, ERBB3 or c-Met. However they exhibit sustained activation of mTORC1 and ERK1/2, as well as phosphorylation of STAT3, STAT5, rpS6 and CREB. Initial sequence analysis of exome and transcriptome reveals the presence of 76 single nucleotide variants/Indels differing between sensitive and resistant cells with 34/76 validated as true mutations present in the genome of lapatinib resistant SKBR3 cells, including mutations in LATS2, MAP3K5, SMAD3 and PDGFRA. This is the first exome sequence analysis to be reported which defines a drug resistant phenotype in ERBB2+ breast cancer. Ongoing work includes investigation of mutations as drug resistance mediators and analysis of copy number variations and gene fusions/translocations to systematically search for molecular alterations, with the goal of providing a rationale for the design of new combination therapies aimed at lapatinib resistance for ERBB2+ breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD01-09.

P2-01-25: Truncated p110 ERBB2 (CTF611) Increases Migration and Invasion of Breast Epithelial Cells by Inhibiting STAT5b Activation

Background: Truncated ERBB2 receptors are present in a subset of human ERBB2+ amplified/overexpressing breast tumors, and are associated with trastuzumab resistance, metastasis, and poor clinical prognosis. However, whether truncated ERBB2 receptors are drivers of metastasis has not been well defined. In this study, we examined effects of full-length (p185) and truncated (p110) ERBB2 on the migration and invasion of human mammary epithelial cells, including HMLE and MCF10A cells.

Material and Methods: Recombinant p185 and p110 ERBB2 were stably expressed in human mammary epithelial cells (HMLE) and MCF10A cells via retroviral vector. Expression of comparable levels of p185 and p110 in cells was confirmed by western blot. The phosphorylation states of downstream signaling proteins including STAT5 were assayed via phosphoproteomics and Collaborative Enzyme Enhanced Reactive (CEER™) immunoassay. The effects of the p110 constructs on cell migration and invasion were investigated by transwell assays. shRNA-encoding lentivirus was used for specific silencing of STAT5b in HMLE cells, and STAT5b silencing was confirmed at the protein level using western blot.

Results and Discussion: Expression of p110 ERBB2 increased cell migration (HMLE, p = 0.04; MCF10A, p< 0.01) and invasion (HMLE, p= 0.03) when compared to expression of p185. Furthermore, expression of p110 in HMLE cells was associated with reduced phosphorylation of STAT5b. shRNA mediated silencing of STAT5b was sufficient to increase the migration (p < 0.01) and invasion of HMLE cells, phenocopying the p110 driven effects on HMLE cells. In clinical studies, loss of activated STAT5 protein correlates with breast cancer progression and is a negative predictor of survival. By analyzing publicly available gene expression datasets, we found that STAT5b mRNA expression is also significantly decreased in breast cancer compared to normal breast tissues in several studies, as well as in ERBB2 amplified vs. nonamplified samples. To our knowledge, this is the first reported perturbation of STAT signaling by truncated ERBB2 receptor, and suggests a mechanism by which truncated p110 ERBB2 (CTF611) increases migration and invasion of breast epithelial cells. This study extends the available data regarding STAT5 loss in breast cancer progression.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-01-25.

Phase 2 study of neoadjuvant treatment with NOV-002 in combination with doxorubicin and cyclophosphamide followed by docetaxel in patients with HER-2 negative clinical stage II-IIIc breast cancer

NOV-002 (a formulation of disodium glutathione disulfide) modulates signaling pathways involved in tumor cell proliferation and metastasis and enhances anti-tumor immune responsiveness in tumor models. The addition of NOV-002 to chemotherapy has been shown to increase anti-tumor efficacy in animal models and some early phase oncology trials. We evaluated the clinical effects of NOV-002 in primary breast cancer, whether adding NOV-002 to standard preoperative chemotherapy increased pathologic complete response rates (pCR) at surgery, and determined whether NOV-002 mitigated hematologic toxicities of chemotherapy and whether levels of myeloid derived suppressor cells (MDSC) were predictive of response. Forty-one women with newly diagnosed stages II-IIIc HER-2 negative breast cancer received doxorubicin-cyclophosphamide followed by docetaxel (AC → T) every 3 weeks and concurrent daily NOV-002 injections. The trial was powered to detect a doubling of pCR rate from 16 to 32% with NOV-002 plus AC → T (α = 0.05, β = 80%). Weekly complete blood counts were obtained as well as circulating MDSC levels on day 1 of each cycle were quantified. Of 39 patients with 40 evaluable tumors, 15 achieved a pCR (38%), meeting the primary endpoint of the trial. Concurrent NOV-002 resulted in pCR rates for AC → T chemotherapy higher than previously reported. Patients with lower levels of circulating MDSCs at baseline and on the last cycle of chemotherapy had significantly higher probability of a pCR (P = 0.02). Further evaluation of NOV-002 in a randomized study is warranted.

Neoadjuvant platinum-based chemotherapy (CT) for triple-negative locally advanced breast cancer (LABC): Retrospective analysis of 125 patients

625

Background: Triple-negative breast cancer (TNBC), defined by lack of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2, accounts for 15–20% of all breast cancers and is associated with poor prognosis. There is no consensus regarding optimal CT for treatment of such patients. Preclinical data suggests TNBC may be sensitive to platinums because of deficiencies in BRCA-associated DNA repair. The aim of this study was to evaluate pathologic complete response (pCR) and overall survival (OS) in patients with TNBC treated with neoadjuvant platinum-based CT. Methods: We identified 674 patients with LABC who received neoadjuvant CT between January 1999 and June 2008 at University of Miami. Of these, 125 (18.5%) had histopathologic confirmation of TNBC. All patients received neoadjuvant platinum salts + docetaxel. 76 (61%) also received neoadjuvant AC, while 42 (34%) received adjuvant AC. pCR was defined as no residual invasive disease in breast and axilla. OS was calculated according to Kaplan-Meier. Results: Demographics: median age 50 (28–86 years). 60% premenopausal. TNM stage distribution: T1 0.9%, T2 5.2%, T3 53.4%, T4 40.5%, N0 25.0%, N1 36.2%, N2 35.4%, N3 3.4%, M0 100%, inflammatory 11%, median tumor size = 9.5 cm. Follow up duration ranged from 0.3 to 8.9 years. pCR was observed in 42 of 125 patients (34%; 95% CI 26–43%). Among patients receiving neoadjuvant AC, 30 of 76 (40%; 95% CI 28–51%) had pCR, while amongst those receiving adjuvant AC, 12 of 42 (29%, 95% CI 16–45%) had pCR at the time of definitive surgery. Patients achieving pCR had significantly higher OS (5-yr rate = 73% in pCR, vs. 49% in non-pCR; p < 0.001). OS in TNBC patients receiving cisplatin/docetaxel was significantly superior to those receiving carboplatin/docetaxel (11 mortality events out of 78 patients receiving cisplatin based CT vs 24 out of 47 receiving carboplatin based CT logrank p = 0.001). Conclusions: To date, this is the largest single institution cohort of locally advanced TNBC uniformly treated with platinum+docetaxel-based CT regimens. Platinum/docetaxel-based neoadjuvant CT provided high rates of pCR and excellent OS for women with locally advanced TNBC.

No significant financial relationships to disclose.

Single-agent lapatinib for HER2-overexpressing advanced or metastatic breast cancer that progressed on first- or second-line trastuzumab-containing regimens

BACKGROUND

This phase II study evaluated the efficacy and safety of lapatinib in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced or metastatic breast cancer that progressed during prior trastuzumab therapy.

PATIENTS AND METHODS

Women with stage IIIB/IV HER2-overexpressing breast cancer were treated with single-agent lapatinib 1250 or 1500 mg once daily after protocol amendment. Tumor response according to RECIST was assessed every 8 weeks. HER2 expression was assessed in tumor tissue by immunohistochemistry and FISH.

RESULTS

Seventy-eight patients were enrolled in the study. Investigator and independent review response rates [complete response (CR) or partial response (PR)] were 7.7% and 5.1%, and clinical benefit rates (CR, PR, or stable disease for >or=24 weeks) were 14.1% and 9.0%, respectively. Median time to progression was 15.3 weeks by independent review, and median overall survival was 79 weeks. The most common treatment-related adverse events were rash (47%), diarrhea (46%), nausea (31%), and fatigue (18%).

CONCLUSIONS

Single-agent lapatinib has clinical activity with manageable toxic effects in HER2-overexpressing breast cancer that progressed on trastuzumab-containing therapy. Studies of lapatinib-based combination regimens with chemotherapy and other targeted therapies in metastatic and earlier stages of breast cancer are warranted.

A phase II study of neoadjuvant docetaxel/carboplatin with or without trastuzumab in locally advanced breast cancer: Response and cardiotoxicity

10515

Background: A phase II clinical trial was conducted to study the safety and efficacy of neoadjuvant docetaxel/carboplatin (T/C) with or without trastuzumab (H) in women with stage III breast cancer. Methods: Forty-eight of 75 planned primary breast cancer patients (T3 or T4, any N, M0), age between 18 and 80 have been enrolled. Four cycles of T (75 mg/m2) + C (AUC 6) were given every 3 weeks preoperatively. Patients with HER-2 amplified tumors (FISH +) were randomized to receive either weekly concurrent H or T/C alone preoperatively and T/C plus H postoperatively. Tumors were assessed clinically at baseline and after neoadjuvant therapy. Cardiac assessment consisted of medical history, EKG and LVEF (by echocardiogram or MUGA) at baseline and at the end of neoadjuvant chemotherapy. Results: Available data from 45 of 48 enrolled patients showed 49% (22 cases) with complete clinical response, with 54.5% being HER-2 (+) (12 cases). Stable disease was seen in one patient who was HER-2 (−) (2.2%). Of 37 with complete pathology verification, 11 (29.7%) showed pathologic complete response (pCR) of the primary tumor with 5 cases being HER-2 (+). Of the 22 HER-2 (+) cases that completed neoadjuvant treatment, 11 received T/C/H and 11 received T/C. pCR was noted in 36.4% of the T/C/H group and 9% of the T/C group. LVEF data is available from 43 patients during the neoadjuvant phase, showing 18.6% (8 cases) with decrease of ≥ 10% (5 patients in the T/C arm and 3 patients in the T/C/H arm), although none had cardiac symptoms or LVEF below the normal limit. Conclusions: T/C ± H is clinically active in patients with locally advanced breast cancer including a 30% pCR rate. The cardiotoxicity rates were comparable between patients who received T/C and T/C/H.

No significant financial relationships to disclose.

Phase I pharmacokinetics (PK) of humanized anti-MUC-1 antibody R1550

2533

Background: MUC-1 glycoprotein establishes a molecular barrier at the epithelial surface, and engages in morphogenetic signal transduction. A 20 amino acid MUC-1 core tandem repeat is aberrantly glycosylated in >90% of epithelial tumors, exposing peptide sequence PDTRP. Humanized IgG1 κ monoclonal antibody R1550 binds PDTRP (Kd∼1nM) and induces potent antibody-dependent cellular cytotoxicity. Methods: R1550 clinical tolerability and PK was determined in advanced, PDTRP-expressing (by IHC), breast cancer patients progressing after anthracyclines and taxanes. Key eligibility: informed consent, WHO PS 0–1, life expectancy >4 mos, non-inflammatory histology, and no CNS metastasis. R1550 was infused IV over 1–3 hrs: cohort 1 (N = 3) 1 mg/kg; cohort 2 (N = 9) 3 mg/kg; cohort 3 (N = 6) 9 mg/kg; cohort 4 (N=3) 16 mg/kg, with repeat dosing every 1–2 weeks (patient-individualized PK assessment) until disease progression. Plasma [R1550] was measured by quantitative ELISA. PK parameters were analyzed by a non-compartmental model, and a 2-compartment population PK model. Results: 21 patients (mean age 54, median # of prior chemotherapy agents = 4) have been dosed. Safety data (n=18): R1550 is generally well tolerated with fatigue (28%), gastrointestinal symptoms (22%), skin rash (17%), pyrexia (11%), and elevated liver function tests (11%) as the most frequently reported adverse events (AEs). Two grade 4 AEs were reported: elevated AST, and hyperglycemia, both in cohort 2. Neither have been observed in expanded or subsequent cohorts. Median number of doses received per patient = 3 (range, 3–4), 4 (1–13) and 6 (4–21), in cohorts 1, 2, and 3, respectively. No anti-humanized antibodies were detected. PK parameters of cohorts 1–3 are shown below. Conclusions: R1550 is well tolerated, with MTD exceeding 9 mg/kg. PK parameters using non-compartmental, and 2-compartment population PK models are in agreement. R1550 half-life suggests weekly dosing. Plasma exposure and dose relationships are linear within 1–9 mg/kg dose range. Accrual to cohort 4 is ongoing.

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Survivin expression in breast cancer predicts clinical outcome and is associated with HER2, VEGF, urokinase plasminogen activator and PAI-1

BACKGROUND

Survivin, a novel inhibitor of apoptosis, is one of the most cancer-specific proteins identified to date. In this study we (a) evaluated the association between survivin and HER2, vascular endothelial growth factor (VEGF) and uPA/PAI-1 expression and (b) defined its effect on clinical outcome in a large breast cancer patient cohort.

PATIENTS AND METHODS

Survivin expression was measured by ELISA in primary breast cancer tissue extracts from 420 patients with long-term clinical follow-up.

RESULTS

Survivin was detected in 378 (90%) of the 420 primary breast cancer cases. Increased survivin levels were significantly associated with high nuclear grade (P < 0.0001), negative hormone receptor status (P = 0.0028), HER2 overexpression (P = 0.0094), VEGF expression (P < 0.0001), high uPA (P = 0.0002) and PAI-1 levels (P = 0.0002). Using the 25th percentile (1.4 ng/mg) as a cut-off point, patients expressing elevated survivin had a significantly worse disease-free survival (DFS: P = 0.0007, RR 1.97) and overall survival (OS: P = 0.0009, RR 2.11) compared with patients expressing lower levels of survivin. In multivariate analysis, this prognostic value of survivin was independent of both traditional and novel clinicopathologic factors for both DFS (P = 0.0076, RR 1.72) and OS (P = 0.0155, RR 1.76).

CONCLUSIONS

The independent prognostic relevance of survivin, when combined with previous data from model systems implicating survivin in the inhibition of apoptosis, suggests that survivin may be a suitable target for future therapeutic strategies.

Combining the anti-HER2 antibody trastuzumab with taxanes in breast cancer: results and trial considerations

Overexpression of the p185/HER2 protein is seen in 20%-25% of primary breast cancers and is associated with poor prognosis. Recent phase II and III clinical trials demonstrate that trastuzumab is active against breast tumors, both as a single agent and in combination with chemotherapy. In patients with HER2-overexpressing metastatic breast cancer, use of trastuzumab in combination with chemotherapy is associated with a 20% reduction in relative risk of death and an increase in median survival from 20.3 to 25.1 months compared to chemotherapy alone. Side effects include fever and chills and an unexpected increase in doxorubicin/trastuzumab-associated cardiomyopathy. Clinical development is now focused on trastuzumab in combination with chemotherapy regimens that do not contain an anthracycline. Trastuzumab in combination with docetaxel is synergistic in vitro. Data from ongoing clinical trials are consistent with this finding. Preliminary data from 3 phase II studies suggest a 44%-63% response rate when the combination is used first or second line in HER2-overexpressing metastatic breast cancer. The combination of docetaxel with trastuzumab is well tolerated and has not been associated with significant cardiotoxicity. Given in vitro evidence that platinum salts act synergistically with trastuzumab and docetaxel, and phase II data suggesting clinical efficacy and good tolerability, the combination of platinum salt plus trastuzumab and docetaxel is now being assessed in adjuvant trials

Docetaxel and herceptin: foundation for future strategies

Randomized controlled studies have demonstrated that both docetaxel and Herceptin are capable of increasing survival in patients with metastatic breast cancer. The two agents show synergy in vitro, and their use in combination is not likely to be associated with the problem of enhanced cardiotoxicity. In two trials of Herceptin plus docetaxel in patients with advanced breast cancer, preliminary data are available for 35 patients. These early results show that the combination is well-tolerated. No symptomatic cardiotoxicity has occurred. The preliminary response rates (RR) in these first- and second-line patients are 44% in one study and 63% in the other. In the subgroups of patients who were HER-2 3+ overexpressers, the RRs are currently 55% and 73%. In an attempt to maximize the efficacy of Herceptin, its use has also been studied in combination with docetaxel and a platinum salt, producing a preliminary RR of 78% in patients positive for HER-2 on the fluorescence in situ hybridization assay. These data are sufficiently promising to justify a study of the role of Herceptin in combination with adjuvant chemotherapy regimens containing docetaxel or docetaxel plus a platinum. The combination of Herceptin with adjuvant therapy containing docetaxel and a platinum may provide a helpful alternative to the potentially cardiotoxic Herceptin/anthracycline-containing regimens currently under investigation.

Trastuzumab and chemotherapeutics: drug interactions and synergies

Previous studies have shown a synergistic interaction between trastuzumab (Herceptin; Genentech, Inc, South San Francisco, CA) and the cytotoxic drug cisplatin in human breast cancer cells. To define the nature of the interaction between trastuzumab and other classes of cytotoxic drugs, we applied multiple drug effect/combination index isobologram analysis to a variety of chemotherapeutic drug/trastuzumab combinations in vitro. Synergistic interactions at clinically relevant drug concentrations were observed for trastuzumab in combination with cisplatin, docetaxel, thiotepa, 4-OH cyclophosphamide, vinorelbine, and etoposide. Additive cytotoxic effects were observed with trastuzumab plus doxorubicin, paclitaxel, methotrexate, and vinblastine. One drug, 5-fluorouracil was found to be antagonistic with trastuzumab in vitro. In vivo drug/trastuzumab studies were conducted with HER-2/neu-transfected MCF7 human breast cancer xenografts in athymic mice. Combinations of trastuzumab plus cisplatin, docetaxel, cyclophosphamide, doxorubicin, paclitaxel, methotrexate, etoposide, and vinblastine in vivo resulted in a significant reduction in xenograft volume compared to chemotherapy-alone controls (P < .05). The synergistic interaction of trastuzumab with specific chemotherapeutic agents suggests rational combinations for testing in human clinical trials.

A model-based approach for assessing in vivo combination therapy interactions

We present an approach for evaluating the efficacy of combination antitumor agent schedules that accounts for order and timing of drug administration. Our model-based approach compares in vivo tumor volume data over a time course and offers a quantitative definition for additivity of drug effects, relative to which synergism and antagonism are interpreted. We begin by fitting data from individual mice receiving at most one drug to a differential equation tumor growth/drug effect model and combine individual parameter estimates to obtain population statistics. Using two null hypotheses: (i) combination therapy is consistent with additivity or (ii) combination therapy is equivalent to treating with the more effective single agent alone, we compute predicted tumor growth trajectories and their distribution for combination treated animals. We illustrate this approach by comparing entire observed and expected tumor volume trajectories for a data set in which HER-2/neu-overexpressing MCF-7 human breast cancer xenografts are treated with a humanized, anti-HER-2 monoclonal antibody (rhuMAb HER-2), doxorubicin, or one of five proposed combination therapy schedules.

Biologic effects of heregulin/neu differentiation factor on normal and malignant human breast and ovarian epithelial cells

The heregulins are a family of ligands with ability to induce phosphorylation of the p185HER-2/neu receptor. Various investigators have reported a variety of responses of mouse and human breast and ovarian cells to this family of ligands including growth stimulation, growth inhibition, apoptosis and induction of differentiation in cells expressing the HER-2/neu receptor. Some of the disparity in the literature has been attributed to variations in the cell lines studied, ligand dose applied, methodologies utilized or model system evaluated (i.e. in vitro or in vivo). To evaluate the effects of heregulin on normal and malignant human breast and ovarian epithelial cells expressing known levels of the HER-2/neu receptor, this report presents the use of several different assays, performed both in vitro and in vivo, in vitro proliferation assays, direct cell counts, clonogenicity under anchorage-dependent and anchorage-independent conditions, as well as the in vivo effects of heregulin on human cells growing in nude mice to address heregulin activity. Using a total of five different biologic assays in nine different cell lines, across two different epithelia and over a one log heregulin dose range, we obtained results that clearly indicate a growth-stimulatory role for this ligand in human breast and ovarian epithelial cells. We find no evidence that heregulin has any growth-inhibitory effects in human epithelial cells. We also quantitated the amount of each member of the type I receptor tyrosine kinase family (RTK I, i.e. HER-1, HER-2, HER-3 and HER-4) in the cell lines employed and correlated this to their respective heregulin responses. These data demonstrate that HER-2/neu overexpression itself affects the expression of other RTK I members and that cells expressing the highest levels of HER-2/neu have the greatest response to HRG.

Combination therapy with trastuzumab (Herceptin) and cisplatin for chemoresistant metastatic breast cancer: evidence for receptor-enhanced chemosensitivity

The anti-HER-2/neu antibody trastuzumab (Herceptin; Genentech, San Francisco, CA) interferes with DNA repair induced by cisplatin and, as a result, promotes cytotoxicity in HER-2/neu-overexpressing tumor target cells in a synergistic fashion. This effect of trastuzumab, termed receptor-enhanced chemosensitivity, is specific for HER-2/neu-overexpressing cells, having no effect on cells without overexpression. Based on these findings, we conducted phase I and II clinical trials of trastuzumab plus cisplatin to determine the toxicity, pharmacokinetics, response rate, and response duration of this combination in patients with HER-2/neu-overexpressing metastatic breast cancer who had demonstrated disease progression (chemoresistance) while on active chemotherapy just prior to study entry. In phase I, four of 15 patients had objective clinical responses, including one complete response of several years' duration. Of 37 assessable patients enrolled in phase II, nine (24.3%) had objective clinical responses and an additional nine had minor responses or stable disease. The median time to progression among the responders was 8.4 months. The toxicity profile reflected that expected from cisplatin alone, with no apparent increase in toxicity caused by the addition of trastuzumab. Moreover, the pharmacokinetics of trastuzumab were unaltered by coadministration of cisplatin. We conclude that the combination of trastuzumab and cisplatin results in response rates higher than that reported for either single agent alone. Such receptor-enhanced chemosensitivity offers a new approach to target overexpressed growth factor receptors in a variety of cancers, which will lead to new, biologically based therapeutic strategies for clinical intervention.

HER-2/neu as a predictive marker of response to breast cancer therapy

Amplification of the HER-2/neu (c-erbB-2) gene resulting in overexpression of the p185HER-2 growth factor receptor occurs in approximately 25% of early stage breast cancers. HER-2/neu has been established as an important independent prognostic factor in early stage breast cancer in large cohorts of patients and in cohorts with very long (30 year) follow-up duration. New data are emerging to suggest that HER-2/neu may be useful not only as a prognostic factor but also as a predictive marker for projecting response to chemotherapeutics, antiestrogens, and therapeutic anti-HER-2/neu monoclonal antibodies. In this review we highlight recent data on HER-2/neu as a predictive marker of response to breast cancer therapy and discuss the clinical implications of this information. The difficulty in comparing results from different data sets due to the wide variety of reagents and technologies used to detect HER-2/neu amplification/overexpression in clinical specimens is also discussed. Finally, we report results from experimental models of HER-2/neu overexpression which have been used in an effort to understand the relationship between HER-2/neu and response to chemotherapeutics and antiestrogens in breast cancer.

Remission of human breast cancer xenografts on therapy with humanized monoclonal antibody to HER-2 receptor and DNA-reactive drugs

HER-2 oncogene encodes a transmembrane growth factor receptor that is overexpressed in 25-30% of patients with primary breast and ovarian cancer. A murine monoclonal antibody, 4D5, to the extracellular domain of HER-2 receptor elicits cytostatic growth inhibition of tumor cells overexpressing HER-2 protein, but clinical use of this antibody is limited by genesis of human anti-mouse antibodies. To avoid this problem, a recombinant humanized 4D5 monoclonal antibody (rhuMAb HER-2) was developed and tested using a human tumor xenograft model. Human breast and ovarian cancer cells which overexpress HER-2 were inhibited in vivo by the rhuMAb HER-2 antibody. Tumor growth relative to control was reduced at all doses of antibody tested, and the magnitude of growth inhibition was directly related to dose of rhuMAb HER-2. Tumor growth resumed on termination of antibody therapy, indicating a cytostatic effect. To elicit a cytotoxic response, human breast tumor xenografts were treated with a combination of antibody and antitumor drugs, cisplatin or doxorubicin. The combination of antibody with either cisplatin or doxorubicin resulted in significantly greater growth inhibition, with the cisplatin combination demonstrating a greater response. In addition, therapy with cisplatin and antireceptor antibody elicited complete tumor remissions after 2-3 cycles of therapy. The schedule of administration of anti-receptor antibody and cisplatin was critical for occurrence of antibody-induced potentiation in cisplatin cytotoxicity. Enhanced killing of tumor cells was found only if antibody and drug were given in close temporal proximity. Since interference with DNA repair pathways may contribute to this receptor-enhanced chemosensitivity, repair of cisplatin-damaged reporter DNA (pCMV-beta) was determined in human breast cells. As in studies of antibody-enhanced cisplatin cytotoxicity in vivo, treatment with rhuMAb HER-2 blocked the repair of cisplatin-damaged DNA only if the antibody was administered in close temporal proximity to transfection of the drug-exposed reporter DNA. An alternative measure of DNA repair, unscheduled DNA synthesis, was also assessed. Treatment with either cisplatin or doxorubicin led to an increase in unscheduled DNA synthesis that was reduced by combined therapy with antireceptor antibody specific to HER-2-overexpressing breast cancer cells. Using a direct measure of DNA repair, therapy of HER-2-overexpressing cells with rhuMAb HER-2 also blocked the removal of cisplatin-induced DNA adducts. Expression of p21/WAF1, an important mediator of DNA repair, was disrupted in breast cancer cells with HER-2 overexpression, but not in control cells, after treatment with HER-2 antibody, thus suggesting cross-communication between the HER-2 signaling and DNA repair pathways. These data demonstrate an in vivo antiproliferative effect of rhuMAb HER-2 on tumors that overexpress HER-2 receptor and a therapeutic advantage in the administration of the antireceptor antibody in combination with chemotherapeutic agents.

Phase II study of receptor-enhanced chemosensitivity using recombinant humanized anti-p185HER2/neu monoclonal antibody plus cisplatin in patients with HER2/neu-overexpressing metastatic breast cancer refractory to chemotherapy treatment

PURPOSE

To determine the toxicity, pharmacokinetics, response rate, and response duration of intravenous (i.v.) administration of recombinant, humanized anti-p185HER2 monoclonal antibody (rhuMAb HER2) plus cisplatin (CDDP) in a phase II, open-label, multicenter clinical trial for patients with HER2/neu-overexpressing metastatic breast cancer.

PATIENTS AND METHODS

The study population consisted of extensively pretreated advanced breast cancer patients with HER2/neu overexpression and disease progression during standard chemotherapy. Patients received a loading dose of rhuMAb HER2 (250 mg i.v.) on day 0, followed by weekly doses of 100 mg i.v. for 9 weeks. Patients received CDDP (75 mg/m2) on days 1, 29, and 57.

RESULTS

Of 37 patients assessable for response, nine (24.3%) achieved a PR, nine (24.3%) had a minor response or stable disease, and disease progression occurred in 19 (51.3%). The median response duration was 5.3 months (range, 1.6-18). Grade III or IV toxicity was observed in 22 of 39 patients (56%). The toxicity profile reflected that expected from CDDP alone with the most common toxicities being cytopenias (n = 10), nausea/vomiting (n = 9), and asthenia (n = 5). Mean pharmacokinetic parameters of rhuMAb HER2 were unaltered by coadministration of CDDP.

CONCLUSION

The use of rhuMAb HER2 in combination with CDDP in patients with HER2/neu-overexpressing metastatic breast cancer results in objective clinical response rates higher than those reported previously for CDDP alone, or rhuMAb HER2 alone. In addition, the combination results in no apparent increase in toxicity. Finally, the pharmacology of rhuMAb HER2 was unaffected by coadministration with CDDP.

The effect of HER-2/neu overexpression on chemotherapeutic drug sensitivity in human breast and ovarian cancer cells

Recent studies indicate that oncogenes may be involved in determining the sensitivity of human cancers to chemotherapeutic agents. To define the effect of HER-2/neu oncogene overexpression on sensitivity to chemotherapeutic drugs, a full-length, human HER-2/neu cDNA was introduced into human breast and ovarian cancer cells. In vitro dose-response curves following exposure to 7 different classes of chemotherapeutic agents were compared for HER-2- and control-transfected cells. Chemosensitivity was also tested in vivo for HER-2- and control-transfected human breast and ovarian cancer xenografts in athymic mice. These studies indicate that HER-2/neu overexpression was not sufficient to induce intrinsic, pleomorphic drug resistance. Furthermore, changes in chemosensitivity profiles resulting from HER-2/neu transfection observed in vitro were cell line specific. In vivo, HER-2/neu-overexpressing breast and ovarian cancer xenografts were responsive to different classes of chemotherapeutic drugs compared to control-treated xenografts with no statistically significant differences between HER-2/neu-overexpressing and nonoverexpressing xenografts. We found no instance in which HER-2/neu-overexpressing xenografts were rendered more sensitive to chemotherapeutic drugs in vivo. HER-2/neu-overexpressing xenografts consistently exhibited more rapid regrowth than control xenografts following initial response to chemotherapy suggesting that a high rate of tumor cell proliferation rather than intrinsic drug resistance may be responsible for the adverse prognosis associated with HER-2/neu overexpression in human cancers.

HER-2 tyrosine kinase pathway targets estrogen receptor and promotes hormone-independent growth in human breast cancer cells

Growth of human breast cells is closely regulated by steroid hormone as well as peptide hormone receptors. Members of both receptor classes are important prognostic factors in human breast cancer. Clinical data indicate that overexpression of the HER-2 gene is associated with an estrogen receptor-negative phenotype. In this study, we demonstrate that introduction of a HER-2 cDNA, converting non-overexpressing breast cancer cells to those which overexpress this receptor, results in development of estrogen-independent growth which is insensitive to both estrogen and the antiestrogen, tamoxifen. Moreover, activation of the HER-2 receptor in breast cancer cells by the peptide growth factor, heregulin, leads to direct and rapid phosphorylation of ER on tyrosine residues. This is followed by interaction between ER and the estrogen-response elements in the nucleus and production of an estrogen-induced protein, progesterone receptor. In addition, overexpression of HER-2 receptor in estrogen-dependent tumor cells promotes ligand-independent down-regulation of ER and a delayed autoregulatory suppression of ER transcripts. These data demonstrate a direct link between these two receptor pathways and suggest one mechanism for development of endocrine resistance in human breast cancers.

Antibody to HER-2/neu receptor blocks DNA repair after cisplatin in human breast and ovarian cancer cells

Approximately 30% of human breast and ovarian cancers have amplification and/or overexpression of HER-2/neu gene which encodes a cell surface growth-factor receptor. Overexpression of this receptor, p185HER-2/neu, is associated with poor outcome and may predict clinical response to chemotherapy. Antibodies to HER-2/neu receptor have a cytostatic effect in suppressing growth of cells with overexpression of p185HER-2/neu. To elicit a cytocidal effect, therapy with antireceptor antibody was used in combination with the DNA-damaging drug, cisplatin, and this combined treatment produced a synergistic decrease in cell growth. In addition, antibody mediated an increased sensitivity to cisplatin in drug-resistant ovarian carcinoma cells containing multiple copies of HER-2/neu gene. To evaluate the mechanism for this synergy, unscheduled DNA synthesis was measured in cancer cells using incorporation of [3H]thymidine and autoradiography, and formation and repair of cisplatin-induced DNA adducts was also measured. Treatment with cisplatin led to a marked, dose-dependent increase in unscheduled DNA synthesis which was significantly reduced by combined treatment with antireceptor antibody in HER-2/neu-overexpressing cells. Therapy with antibody to HER-2/neu receptor also led to a 35-40% reduction in repair of cisplatin-DNA adducts after cisplatin exposure and, as a result, promoted drug-induced killing in target cells. This phenomenon which we term receptor-enhanced chemosensitivity may provide a rationale for more selective targeting and exploitation of overexpressed growth factor receptors in cancer cells, thus leading to new strategies for clinical intervention.

Diagnosis of infective and inflammatory disorders by flow cytometric analysis of blood neutrophils

The utility of neutrophil parameters provided by two flow cytometric hematologic analyzers (the H-1 and H6000, Technicon Instruments Corporation, Tarrytown, NY) was investigated for the diagnosis of infective and/or inflammatory disorders. The test population of 156 hospital patients was selected on the basis of a blood culture request. Positivity or negativity for infective and/or inflammatory disease was inferred from chart review. The parameters evaluated included the absolute neutrophil count, the lobularity index, and the left shift flag from the H-1, the percentage of high peroxidase cells from the H6000, the routine laboratory band count, and a reference band count. Significant intercorrelations were observed between these parameters. The diagnostic performance of the routine laboratory band count was significantly inferior to that of all other parameters. At equivalent points on their receiver operating characteristic curves, the diagnostic efficiencies of the remaining tests ranged from 61.5% for the lobularity index to 67% for the left shift flag and the percentage of high peroxidase cells. These differences were not significant statistically.