Systemic treatment of brain metastases in HER2-positive breast cancer: current status and future directions

Current progress in chimeric antigen receptor-modified T cells for the treatment of metastatic breast cancer

Breast cancer is the leading cancer in women. Around 20-30% breast cancer patients undergo invasion or metastasis after radical surgical resection and eventually die. Number of breast cancer patients show poor sensitivity toward treatments despite the advances in chemotherapy, endocrine therapy, and molecular targeted treatments. Therapeutic resistance and tumor recurrence or metastasis develop with the ongoing treatments. Conducive treatment strategies are thus required. Chimeric antigen receptor (CAR)-modified T-cell therapy has progressed as a part of tumor immunotherapy. However, CAR-T treatment has not been effective in solid tumors because of tumor microenvironment complexity, inhibitory effects of extracellular matrix, and lacking ideal tumor antigens. Herein, the prospects of CAR-T cell therapy for metastatic breast cancer are discussed, and the targets for CAR-T therapy in breast cancer (HER-2, C-MET, MSLN, CEA, MUC1, ROR1, EGFR) at clinical level are reviewed. Moreover, solutions are proposed for the challenges of breast cancer CAR-T therapy regarding off-target effects, heterogeneous antigen expression by tumor cells and immunosuppressive tumor microenvironment. Ideas for improving the therapeutics of CAR-T cell therapy in metastatic breast cancer are suggested.

Emerging Targeted Therapies for HER2-Positive Breast Cancer

Breast cancer is the most common cancer in women and the leading cause of death. HER2 overexpression is found in approximately 20% of breast cancers and is associated with a poor prognosis and a shorter overall survival. Tratuzumab, a monoclonal antibody directed against the HER2 receptor, is the standard of care treatment. However, a third of the patients do not respond to therapy. Given the high rate of resistance, other HER2-targeted strategies have been developed, including monoclonal antibodies such as pertuzumab and margetuximab, trastuzumab-based antibody drug conjugates such as trastuzumab-emtansine (T-DM1) and trastuzumab-deruxtecan (T-DXd), and tyrosine kinase inhibitors like lapatinib and tucatinib, among others. Moreover, T-DXd has proven to be of use in the HER2-low subtype, which suggests that other HER2-targeted therapies could be successful in this recently defined new breast cancer subclassification. When patients progress to multiple strategies, there are several HER2-targeted therapies available; however, treatment options are limited, and the potential combination with other drugs, immune checkpoint inhibitors, CAR-T cells, CAR-NK, CAR-M, and vaccines is an interesting and appealing field that is still in development. In this review, we will discuss the highlights and pitfalls of the different HER2-targeted therapies and potential combinations to overcome metastatic disease and resistance to therapy.

A novel ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases

Pancreatic ribonuclease is known to participate in host defense system against pathogens, such as parasites, bacteria, and virus, which results in innate immune response. Nevertheless, its potential impact to host cells remains unclear. Of interest, several ribonucleases do not act as catalytically competent enzymes, suggesting that ribonucleases may be associated with certain intrinsic functions other than their ribonucleolytic activities. Most recently, human pancreatic ribonuclease 5 (hRNase5; also named angiogenin; hereinafter referred to as hRNase5/ANG), which belongs to the human ribonuclease A superfamily, has been demonstrated to function as a ligand of epidermal growth factor receptor (EGFR), a member of the receptor tyrosine kinase family. As a newly identified EGFR ligand, hRNase5/ANG associates with EGFR and stimulates EGFR and the downstream signaling in a catalytic-independent manner. Notably, hRNase5/ANG, whose level in sera of pancreatic cancer patients, serves as a non-invasive serum biomarker to stratify patients for predicting the sensitivity to EGFR-targeted therapy. Here, we describe the hRNase5/ANG-EGFR pair as an example to highlight a ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases, which are thought as two unrelated protein families associated with distinct biological functions. The notion of serum biomarker-guided EGFR-targeted therapies will also be discussed. Furthering our understanding of this novel ligand-receptor interaction will shed new light on the search of ligands for their cognate receptors, especially those orphan receptors without known ligands, and deepen our knowledge of the fundamental research in membrane receptor biology and the translational application toward the development of precision medicine.

Antibody pharmacokinetics in rat brain determined using microdialysis

Here, we present the first case-study where microdialysis is used to investigate the pharmacokinetics of antibody in different regions of rat brain. Endogenous IgG was used to understand antibody disposition at steady-state and exogenously administered trastuzumab was used to understand the disposition in a dynamic setting. Microdialysis samples from the striatum (ST), lateral ventricle (LV), and cisterna magna (CM) were collected, along with plasma and brain homogenate, to comprehensively understand brain pharmacokinetics of antibodies. Antibody concentrations in cerebrospinal fluid (CSF) were found to vary based on the site-of-collection, where CM concentrations were several-fold higher than LV. In addition, antibody concentrations in CSF (CM/LV) were found to not accurately represent the concentrations of antibody inside brain parenchyma (e.g., ST). Elimination of CSF from CM was found to be slower than LV, and the entry and exit of antibody from ST was also slower. Pharmacokinetics of exogenously administered antibody revealed that the entry of antibody into LV via the blood-CSF barrier may represent an early pathway for antibody entry into the brain. Plasma concentrations of antibody were 247-667, 104-184, 165-435, and 377-909 fold higher than the antibody concentrations in LV, CM, ST, and brain homogenate. It was found that the measurement of antibody pharmacokinetics in different regions of the brain using microdialysis provides an unprecedented insight into brain disposition of antibody. This insight can help in designing better molecules, dosing regimens, and route of administration, which can in turn improve the efficacy of antibodies for central nervous system disorders.

Regional Delivery of Chimeric Antigen Receptor-Engineered T Cells Effectively Targets HER2+ Breast Cancer Metastasis to the Brain

Purpose: Metastasis to the brain from breast cancer remains a significant clinical challenge, and may be targeted with CAR-based immunotherapy. CAR design optimization for solid tumors is crucial due to the absence of truly restricted antigen expression and potential safety concerns with "on-target off-tumor" activity. Here, we have optimized HER2-CAR T cells for the treatment of breast to brain metastases, and determined optimal second-generation CAR design and route of administration for xenograft mouse models of breast metastatic brain tumors, including multifocal and leptomeningeal disease.Experimental Design: HER2-CAR constructs containing either CD28 or 4-1BB intracellular costimulatory signaling domains were compared for functional activity in vitro by measuring cytokine production, T-cell proliferation, and tumor killing capacity. We also evaluated HER2-CAR T cells delivered by intravenous, local intratumoral, or regional intraventricular routes of administration using in vivo human xenograft models of breast cancer that have metastasized to the brain.Results: Here, we have shown that HER2-CARs containing the 4-1BB costimulatory domain confer improved tumor targeting with reduced T-cell exhaustion phenotype and enhanced proliferative capacity compared with HER2-CARs containing the CD28 costimulatory domain. Local intracranial delivery of HER2-CARs showed potent in vivo antitumor activity in orthotopic xenograft models. Importantly, we demonstrated robust antitumor efficacy following regional intraventricular delivery of HER2-CAR T cells for the treatment of multifocal brain metastases and leptomeningeal disease.Conclusions: Our study shows the importance of CAR design in defining an optimized CAR T cell, and highlights intraventricular delivery of HER2-CAR T cells for treating multifocal brain metastases. Clin Cancer Res; 24(1); 95-105. ©2017 AACR.

Effect of Oncoxin Oral Solution in HER2-Overexpressing Breast Cancer

One of the most aggressive breast cancer subtypes includes tumors with high expression of HER2. Gene expression and functional studies have shown a link between HER2 overexpression and oxidative stress. Because of this, we hypothesized that Oncoxin Oral Solution (OOS), a composite product that contains several antioxidants, could have an antitumoral effect against HER2+ tumors. Dose-response studies, biochemical and cytometric assessment of the effect of OOS on cell cycle and apoptosis, and drug combination analyses were performed on BT474 and SKBR3 cells, 2 HER2-overexpressing breast cancer cell lines. OOS reduced the proliferation of these cells, and augmented the action of lapatinib, a HER2 inhibitor used in the breast cancer clinic. Moreover, OOS decreased growth of HER2+ tumors in mice. Mechanistically, OOS provoked cell cycle blockade through upregulation of p27 expression and downregulation of cyclin D levels. OOS also caused apoptotic cell death in HER2+ breast cancer cells, as indicated by increases in PARP cleavage as well as upregulation of caspase 8 and caspase 3 activities. These results demonstrate an antitumoral action of OOS in preclinical models of HER2+ breast cancer and suggest that it can be used with anti-HER2 therapies currently adopted as standard of care in the oncology clinic.

Analysis of gene expression of secreted factors associated with breast cancer metastases in breast cancer subtypes

Breast cancer is a heterogeneous disease, having multiple subtypes with different malignant phenotypes. The triple-negative breast cancer, or basal breast cancer, is highly aggressive, metastatic, and difficult to treat. Previously, we identified that key molecules (IL6, CSF2, CCL5, VEGFA, and VEGFC) secreted by tumor cells and stromal cells in basal breast cancer can promote metastasis. It remains to assess whether these molecules function similarly in other subtypes of breast cancer. Here, we characterize the relative gene expression of the five secreted molecules and their associated receptors (GP130, GMRA, GMRB, CCR5, VEGFR2, NRP1, VEGFR3, NRP2) in the basal, HER2 (human epidermal growth factor receptor 2) positive, luminal A, and luminal B subtypes using high throughput data from tumor samples in The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC). IL6 and CCL5 gene expression are basal breast cancer specific, whereas high gene expression of GP130 was observed in luminal A/B. VEGFA/C and CSF2 mRNA are overexpressed in HER2 positive breast cancer, with VEGFA and CSF2 also overexpressed in basal breast cancer. Further study of the specific protein function of these factors within their associated cancer subtypes may yield personalized biomarkers and treatment modalities.

Pattern of rash, diarrhea, and hepatic toxicities secondary to lapatinib and their association with age and response to neoadjuvant therapy: analysis from the NeoALTTO trial

PURPOSE

We investigated the pattern of rash, diarrhea, and hepatic adverse events (AEs) secondary to lapatinib and their association with age and pathologic complete response (pCR) in the Neoadjuvant Lapatinib and/or Trastuzumab Treatment Optimisation (NeoALLTO) phase III trial.

PATIENTS AND METHODS

Patients with HER2-positive early breast cancer were randomly assigned to receive lapatinib (Arm A), trastuzumab (Arm B), or their combination (Arm C) for 6 weeks followed by the addition of paclitaxel for 12 weeks before surgery. We investigated the frequency and time to developing each AE according to age (≤ 50 v > 50 years) and their association with pCR in a logistic regression model adjusted for age, hormone receptors, tumor size, nodal status, planned breast surgery, completion of lapatinib administration, and treatment arm.

RESULTS

Only patients randomly assigned to arms A and C were eligible (n = 306). Younger patients (≤ 50 years) experienced significantly more rash compared with older patients (74.4% v 47.9%; P < .0001). Diarrhea and hepatic AEs were observed in 78.8% and 41.2% of patients, respectively, with no differences in rate or severity or time of onset according to age. Early rash (ie, before starting paclitaxel) was independently associated with a higher chance of pCR, mainly in patients older than 50 years (odds ratio [OR] = 3.76; 95% CI, 1.69 to 8.34) but not in those ≤ 50 years (OR = 0.92; 95% CI, 0.45 to 1.88; P for interaction = .01). No significant association was observed between pCR and diarrhea or hepatic AEs.

CONCLUSION

Our results indicate that the frequency and clinical relevance of lapatinib-related rash is largely dependent on patient age.

Effect of adjuvant trastuzumab treatment in conventional clinical setting: an observational retrospective multicenter Italian study

Clinical trials have shown the efficacy of trastuzumab-based adjuvant therapy in HER2-positive breast cancers, but routine clinical use awaits evaluation of compliance, safety, and effectiveness. Adjuvant trastuzumab-based therapy in routine clinical use was evaluated in the retrospective study GHEA, recording 1,002 patients treated according to the HERA protocol between March 2005 and December 2009 in 42 Italian oncology departments; 874 (87.23 %) patients completed 1-year trastuzumab treatment. In 128 patients (12.77 %), trastuzumab was withdrawn due to cardiac or non-cardiac toxicity (28 and 29 patients, respectively), disease progression (5 patients) or the clinician's decision (66 patients). In addition, 156 patients experienced minor non-cardiac toxicities; 10 and 44 patients showed CHF and decreased LVEF, respectively, at the end of treatment. Compliance and safety of adjuvant trastuzumab-based therapy in Italian hospitals were high and close to those reported in the HERA trial. With a median follow-up of 32 months, 107 breast cancer relapses were recorded (overall frequency, 10.67 %), and lymph node involvement, estrogen receptor negativity, lymphoid infiltration, and vascular invasion were identified as independent prognostic factors for tumor recurrence, indicating that relapses were associated with advanced tumor stage. Analysis of site and frequency of distant metastases showed that bone metastases were significantly more frequent during or immediately after trastuzumab (<18 months from the start of treatment) compared to recurrences in bone after the end of treatment and wash-out of the drug (>18 months from the start of treatment) (35.89 vs. 14.28 %, p = 0.0240); no significant differences were observed in recurrences in the other recorded body sites, raising the possibility that the protection exerted by trastuzumab is lower in bone metastases.

Surgical resection of brain metastases-impact on neurological outcome

Brain metastases (BM) develop in about 30% of all cancer patients. Surgery plays an important role in confirming neuropathological diagnosis, relieving mass effects and improving the neurological status. To select patients with the highest benefit from surgical resection, prognostic indices (RPA, GPA) have been formulated which are solely focused on survival without considering neurological improvement. In this study we analyzed the impact of surgical resection on the neurological status in addition to overall survival in 206 BM patients. Surgical mortality and morbidity was 0.0% and 10.3% respectively. New neurologic deficits occurred in 6.3% of all patients. The median overall survival was 6.3 months. Poor RPA class and short time interval between diagnosis of cancer and the occurrence of BM were independent factors predictive for poor survival. Improvement of neurological performance was achieved in 56.8% of all patients, with the highest improvement rate seen in patients presenting with increased intracranial pressure and hemiparesis. Notably, the neurological benefits were independent from RPA class. In conclusion, surgical resection leads to significant neurological improvement despite poor RPA class and short overall survival. Considering the low mortality and morbidity rates, resection should be considered as a valid option to increase neurological function and quality of life for patients with BM.

Synergistic Effect between Sphingosine-1-Phosphate and Chemotherapy Drugs against Human Brain-metastasized Breast Cancer MDA-MB-361 cells

Sphingosine-1-phosphate (S1P) is an important sphingolipid metabolite regulating key physiological and pathophysiological processes such as cell growth and survival and tumor angiogenesis. Significant research evidence links elevated cellular S1P concentration to cancer cell proliferation, migration and angiogenesis. Physiological levels of S1P are tightly regulated and maintained at the low nanomolar level. In cancer, S1P may exist well beyond the low nanomolar level. Recently, we reported that S1P selectively induces cell apoptosis of the breast cancer MCF7 cell line at concentrations higher than 1 µM and co-administration of 1 µM S1P significantly increased the cytotoxicity of chemotherapy drug docetaxel. In this study, we show that S1P caused minor increases in cell proliferation or apoptosis, in a concentration-dependent manner, yet co-administration of 10 µM S1P exhibited a significant synergistic effect with chemotherapy drugs docetaxel, doxorubicin and cyclophosphamide. S1P increased the cytotoxic potential of each drug by 2-fold, 3-fold, and 10-fold, respectively, against the breast cancer metastatic cell line MDA-MB-361. This synergism may suggest improved anticancer drug therapy by co-administration of exogenous S1P.