HER2 siRNA Research Articles

HER2 siRNA Facilitated Gene Silencing Coupled with Doxorubicin Delivery: A Dual Responsive Nanoplatform Abrogates Breast Cancer.

The present study investigated the concurrent delivery of antineoplastic drug, doxorubicin, and HER2 siRNA through a targeted theranostic metallic gold nanoparticle designed using polysaccharide, PSP001. The as-synthesized HsiRNA@PGD NPs were characterized in terms of structural, functional, physicochemical, and biological properties. HsiRNA@PGD NPs exposed adequate hydrodynamic size, considerable ζ potential, and excellent drug/siRNA loading and encapsulation efficiency. Meticulous exploration of the biocompatible dual-targeted nanoconjugate exhibited an appealing biocompatibility and pH-sensitive cargo release kinetics, indicating its safety for use in clinics. HsiRNA@PGD NPs deciphered competent cancer cell internalization, enhanced cytotoxicity mediated via the induction of apoptosis, and excellent downregulation of the overexpressing target HER2 gene. Further in vivo explorations in the SKBR3 xenograft breast tumor model revealed the appealing tumor reduction properties, selective accumulation in the tumor site followed by significant suppression of the HER2 gene which contributed to the exclusive abrogation of breast tumor mass by the HsiRNA@PGD NPs. Compared to free drugs or the monotherapy constructs, the dual delivery approach produced a synergistic suppression of breast tumors both in vitro and in vivo. Hence the drawings from these findings implicate that the as-synthesized HsiRNA@PGD NPs could offer a promising platform for chemo-RNAi combinational breast cancer therapy.

Abstract A007: Modulation of HER2 as a mechanism for AR expression

Abstract Background: Intense neoadjuvant androgen deprivation therapy (inADT) is an emerging treatment paradigm for localized high-risk prostate cancer, but in certain patients a subset of tumors will recur after surgery. In tumors with endogenously low androgen receptor (AR) activity, expression of the EGFR family protein HER2 was enriched. We sought to investigate the role of HER2 in driving the proliferation of prostate cancer under androgen-depleted environments. We hypothesized that overexpression of HER2 would decrease AR activity, while its knockdown would conversely increase AR expression beyond baseline levels. Methods: The AR-expressing 22Rv1 and LNCaP prostate cancer cell lines were cultured and plated for transfection. HER2 overexpression was achieved using an exogenous HER2 (ERBB2) plasmid, while HER2 knockdown was performed using siRNA, alongside controls for both groups. Cell lysates were collected at 24-, 48-, and 72-hour time points. Western blotting was performed to examine HER2, AR, PSA, and actin expression. Results: Western blot analysis confirmed successful overexpression and knockdown of HER2, using an exogenous HER2 plasmid and siRNA, respectively. In 22Rv1 and LNCaP cells overexpressing HER2, AR (and AR-V7 in 22Rv1 cells) levels were decreased compared to the control cells. Conversely, 22Rv1 and LNCaP cells with knockdown of HER2 exhibited elevated AR expression. Biological replicates to confirm these findings are in progress. Additional studies will also examine the impact of HER2 signaling and activity on downstream pro-proliferative pathways. Conclusions: Manipulation of HER2 expression highlights a potential role of EGFR family proteins as a mechanism for prostate cancer growth in androgen-deprived environments. Future studies will validate this finding at the RNA level using qPCR and probe downstream targets of HER2 using western blotting. These preliminary findings have implications for the treatment of advanced tumors for which inADT is not a viable option. Targeting HER2 and its downstream signaling pathways represent an intriguing mechanism to overcome resistance to androgen deprivation therapy in newly-diagnosed, treatment-naïve patients. Citation Format: Daniel K.Y. Low, Scott Wilkinson, Isaiah M. King, Shana Y. Trostel, Adam G. Sowalsky. Modulation of HER2 as a mechanism for AR expression [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A007.

Targeted Nanoparticle for Co‐delivery of HER2 siRNA and a Taxane to Mirror the Standard Treatment of HER2+ Breast Cancer: Efficacy in Breast Tumor and Brain Metastasis (Small 11/2022)

Breast Cancer Treatment In article number 2107550, Wassana Yantasee and co-workers develop polymer-decorated mesoporous silica nanoparticles for HER2-positive breast cancer treatment. This patented versatile platform can co-deliver multiple therapeutic classes to ensure that they reach the target cells at the same time to fully realize their synergy. Illustrated herein are nanoparticles with three drug cargos: HER2 antibody, HER2 siRNA, and chemotherapeutic docetaxel.

Targeted Nanoparticle for Co-delivery of HER2 siRNA and a Taxane to Mirror the Standard Treatment of HER2+ Breast Cancer: Efficacy in Breast Tumor and Brain Metastasis.

The first-line treatment of advanced and metastatic human epidermal growth factor receptor type 2 (HER2+) breast cancer requires two HER2-targeting antibodies (trastuzumab and pertuzumab) and a taxane (docetaxel or paclitaxel). The three-drug regimen costs over $320,000 per treatment course, requires a 4 h infusion time, and has many adverse side effects, while achieving only 18 months of progression-free survival. To replace this regimen, reduce infusion time, and enhance efficacy, a single therapeutic is developed based on trastuzumab-conjugated nanoparticles for co-delivering docetaxel and siRNA against HER2 (siHER2). The optimal nanoconstruct has a hydrodynamic size of 100nm and specifically treats HER2+ breast cancer cells over organ-derived normal cells. In a drug-resistant orthotopic HER2+ HCC1954 tumor mouse model, the nanoconstruct inhibits tumor growth more effectively than the docetaxel and trastuzumab combination. When coupled with microbubble-assisted focused ultrasound that transiently disrupts the blood brain barrier, the nanoconstruct inhibits the growth of trastuzumab-resistant HER2+ BT474 tumors residing in the brains of mice. The nanoconstruct has a favorable safety profile in cells and in mice. Combination therapies have become the cornerstone of cancer treatment and this versatile nanoparticle platform can co-deliver multiple therapeutic types to ensure that they reach the target cells at the same time to realize their synergy.

PS02.153: HER2 PATHWAY CONTROL SENSITIVITY TO CISPLATIN IN ESOPHAGEAL ADENOCARCINOMA CELL LINES

Abstract Background Adenocarcinoma of the esophagus is increasing in frequency and is the 6th most common cause of cancer death in North America. Cisplatin has been the backbone of neoadjuvant therapy but despite improved 5-year survival with neoadjuvant chemoradiation, many tumor cells survive chemotherapy leading to distant metastases. This study investigated the molecular changes in tumors when they become cisplatin resistant by focussing on the HER family of proteins. Methods We created 2 cisplatin resistant cell lines and a matching control by exposing the adenocarcinoma cell lines SK-GT-4 and FLO-1 to repeated cycles of cisplatin. Resistance to cisplatin was assessed at the end of the treatment. The expression levels of the HER family members was assessed. Cell proliferation, resistance to cisplatin and siRNA transfection were used to assess the role of HER family members in cisplatin resistance in EAC. Results The cisplatin resistant cell line displayed a lower rate of proliferation than the matching control (1.5 fold difference after 72h, P < 0.05). When the level of HER family members in the cisplatin resistant and control cell lines were measured, we observed a downregulation of HER2 in both cisplatin resistant cell lines (FLO-1: 78.31 mean expression (control) vs 17.43 mean expression (cisplatin resistant), P < 0.05), whereas the EGFR level were unchanged (FLO-1: 154.76 mean expression (control) vs 137.64 mean expression (cisplatin resistant), P > 0.05). In order to confirm this observation, we downregulated HER2 by siRNA and by a HER2 specific inhibitor in control cells. Resistance to cisplatin was similar to the cisplatin resistant cell lines (3.33μM cisplatin for 72h, death rate: 72.1% control vs 23.6% HER2 siRNA, P < 0.05). Similar results were observed in two other EAC cell lines (OE33 And JHESO-AD1). Conclusion Our results suggest that there is a correlation between HER2 level/activity and cisplatin resistance in EAC cells. It appears that as EAC cells acquire cisplatin resistance, they block the HER2 pathway. Disclosure All authors have declared no conflicts of interest.

Lack of acquired resistance in HER2-positive breast cancer cells after long-term HER2 siRNA nanoparticle treatment.

Intrinsic and acquired resistance to current HER2 targeted therapies remains a challenge in clinics. We have developed a therapeutic HER2 siRNA delivered using mesoporous silica nanoparticles modified with polymers and conjugated with HER2 targeting antibodies. Our previous studies have shown that our HER2 siRNA nanoparticles could overcome intrinsic and acquired resistance to trastuzumab and lapatinib in HER2-positive breast cancers. In this study, we investigated the effect of long-term (7 months) treatment using our therapeutic HER2 siRNA. Even after the removal of HER2 siRNA, the long-term treated cells grew much slower (67% increase in doubling time) than cells that have not received any treatment. The treated cells did not undergo epithelial-mesenchymal transition or showed enrichment of tumor initiating cells. Unlike trastuzumab and lapatinib, which induced resistance in BT474 cells after 6 months of treatment, HER2 siRNA did not induce resistance to HER2 siRNA, trastuzumab, or lapatinib. HER2 ablation with HER2 siRNA prevented reactivation of HER2 signaling that was observed in cells resistant to lapatinib. Altogether, our results indicate that a HER2 siRNA based therapeutic provides a more durable inhibition of HER2 signaling in vitro and can potentially be more effective than the existing therapeutic monoclonal antibodies and small molecule inhibitors.

Abstract 471: HER2 regulates PARP-1 expression by suppressing the let-7a microRNA in HER2+ breast cancer

Abstract Background: HER2+ breast cancers are sensitive to PARP inhibition and express elevated levels of the PARP-1 protein. However, the mode of regulation of PARP-1 expression by HER2 is not well understood. MicroRNAs are small non-coding RNAs that function in RNA silencing and post-transcriptional regulation of gene expression. In this study, we investigate whether PARP1 expression in human breast cancer cells is regulated by HER2 regulation of microRNAs. Methods: Human HER2+ breast cancer cell lines BT-474 and SKBR3 were used in this study. MDA-MB-231 (non-HER2 expressing breast cancer cells) stably transfected with a HER2 wild-type plasmid (231 HER2) or the vector control (231 NEO) were also utilized. To identify candidate microRNAs regulated by HER2 overexpression, we performed the nCounter miRNA Expression Assay. MicroRNA and mRNA expression were validated via qRT-PCR analysis in breast cancer cell lines or patient primary tumors. Cells were also transfected with a HER2 siRNA, a let-7a mimic, and an inhibitor of let-7a as well as their respective controls. Western blot analysis and firefly luciferase assays were used to determine whether the 3’UTR of PARP1 was being directly targeted by the let-7a microRNA. Results: HER2 did not regulate PARP-1 at the mRNA level but increased PARP-1 protein in HER2+ breast cancer cells. Specifically, ectopic HER2 overexpression correlated with increased PARP-1 protein levels in the 231 HER2 cell line. Conversely, silencing HER2 reduced PARP-1 protein levels in the BT-474 and SKBR3 cell lines. NanoString nCounter analysis revealed that the HER2+ breast cancer cell lines expressed low levels of the let-7a microRNA. Further, let-7a expression was upregulated after HER2 knockdown in the two native HER2+ breast cancer cell lines. The let-7a mimic also reduced both PARP1 protein expression and luciferase activity in the 231 HER2 and BT-474 cell lines, whereas the let-7a inhibitor reversed these effects in the 231 NEO cell line. Importantly, human HER2+ breast tumors expressed higher levels of PARP-1 and lower levels of let-7a; whereas, the HER2- breast tumors expressed lower levels of PARP-1 and higher levels of let-7a. Further, overexpression of the let-7a mimic reduced cell proliferation in HER2+ breast cancer cells. Conclusions: These results suggest that let-7a regulates PARP-1 expression in HER2+ breast tumors. Let-7a may also be a potential therapeutic target and predictive biomarker of PARPi sensitivity in HER2+ breast cancer patients. Citation Format: Eddy Shih-Hsin Yang, Monicka Wielgos, Rajani Rajbhandari, Shi Wei, Susan Nozell. HER2 regulates PARP-1 expression by suppressing the let-7a microRNA in HER2+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 471. doi:10.1158/1538-7445.AM2017-471

PD-L1 overexpression is partially regulated by EGFR/HER2 signaling and associated with poor prognosis in patients with non-small-cell lung cancer.

Immunocheckpoint inhibitors targeting the programmed cell death-1 (PD-1) and PD-1 ligand 1 (PD-L1) axis have shown promising results in patients with non-small-cell lung cancer (NSCLC). Recent research has shown that epidermal growth factor receptor (EGFR) signaling affects PD-L1 expression in NSCLC cells; however, the mechanism regulating PD-L1 expression in tumor cells remains unclear. Using immunohistochemistry, we evaluated the impact of expression of PD-L1 and EGF family receptors EGFR and human epidermal growth factor receptor 2 (HER2) in tumor cells from 91 patients with pathological Stage IA-IIIA NSCLC. Overexpression of PD-L1 was observed in 14% of the resected tumors, and associated with poor recurrence-free survival (p = 0.021) and overall survival (p = 0.033). PD-L1 expression is positively correlated with EGFR expression and inversely correlated with HER2. NSCLC cell lines were treated in vitro with the EGFR ligand EGF with or without inhibition of EGFR or HER2, after which PD-L1 expression was evaluated using flow cytometry. Consistent with previous reports, PD-L1 expression was clearly enhanced by EGF. EGFR-tyrosine kinase inhibitors or EGFR small interfering RNA (siRNA) blocked EGF-induced PD-L1 overexpression in NSCLC cell lines, but HER2 siRNA did not. Moreover, our findings suggest that PD-L1 expression could be partially regulated via the PI3K/AKT and JAK/STAT pathways. We conclude that PD-L1 overexpression is associated with poor prognosis and is positively correlated with EGFR expression but inversely correlated with HER2 expression in NSCLC. We also showed that EGFR and HER2 have different effects on EGF-induced PD-L1 expression in NSCLC cell lines.

Abstract B11: HER2 regulates PARP-1 expression via the let-7a microRNA in HER2+ breast cancer

Abstract Background: HER2+ breast cancers are sensitive to PARP inhibition and express elevated levels of the PARP-1 protein. However, the mode of regulation of PARP-1 expression by HER2 is not well understood. In this study, we report that the let-7a microRNA is regulating PARP-1 expression at the post-transcriptional level in HER2+ breast cancer cells. Methods: Human HER2+ breast cancer cell lines BT-474 and SKBR3 were used in this study. MDA-MB-231 (non-HER2 expressing breast cancer cells) were also stably transfected with a HER2 wild-type plasmid (231 HER2) or the vector control (231 NEO). Further, to identify candidate microRNAs regulated by HER2 overexpression we used the nCounter miRNA Expression Assay. MicroRNA and mRNA expression were validated via qRT-PCR analysis in breast cancer cell lines or patient primary tumors. Cells were also transfected with a HER2 siRNA, a let-7a mimic, and an inhibitor of let-7a as well as their respective controls. Western blot analysis and firefly luciferase assays were used to determine whether the 3'UTR of PARP1 was being directly targeted by the let-7a microRNA. Results: HER2 did not regulate PARP-1 at the mRNA level but increased PARP-1 protein in HER2+ breast cancer cells. Specifically, ectopic HER2 overexpression correlated with increased PARP-1 protein levels in the 231 HER2 cell line. Conversely, silencing HER2 reduced PARP-1 protein levels in the BT-474 and SKBR3 cell lines. NanoString nCounter analysis revealed that the HER2+ breast cancer cell lines expressed low levels of the let-7a microRNA. Further, let-7a expression was upregulated after HER2 knockdown in the two native HER2+ breast cancer cell lines. The let-7a mimic also reduced both PARP1 protein expression and luciferase activity in the 231 HER2 and BT-474 cell lines, whereas the let-7a inhibitor reversed these effects in the 231 NEO cell line. Importantly, HER2+ breast tumors expressed higher levels of PARP-1 and lower levels of let-7a; whereas, the HER2- breast tumors expressed lower levels of PARP-1 and higher levels of let-7a. Conclusions: These results suggest that let-7a regulates PARP-1 expression in HER2+ breast tumors. Let-7a may also be a potential therapeutic target and predictive biomarker of PARPi sensitivity in HER2+ breast cancer patients. Citation Format: Monicka Wielgos, Rajani Rajbhandari, Susan Nozell, Shi Wei, Eddy S. Yang. HER2 regulates PARP-1 expression via the let-7a microRNA in HER2+ breast cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr B11.

Dimerization of EGFR and HER2 induces breast cancer cell motility through STAT1-dependent ACTA2 induction.

The dimerization of EGFR and HER2 is associated with poor prognosis such as induction of tumor growth and cell invasion compared to when EGFR remains as a homodimer. However, the mechanism for events after dimerization in breast cancer models is not clear. We found that expressions of alpha-smooth muscle actin (ACTA2) and signal transducer and activator of transcription 1 (STAT1) significantly increased with transient or stable overexpression of HER2 in EGFR-positive breast cancer cells. ACTA2 and STAT1 expression was also increased in HER2-positive breast cancer patients. In contrast, ACTA2 expression was decreased by HER2 siRNA. Next, we investigated the co-relation between STAT1 and ACTA2 expression. Basal ACTA2 expression was significantly decreased by treatment with the STAT1 inhibitor fludarabine or the JAK2 inhibitor AG490. In contrast, ACTA2 expression was increased by STAT1 overexpression. Levels of ACTA2, STAT1, and HER2 were increased and relapse free survival was decreased in high-risk breast cancer patients. We also investigated the effect of ACTA2 on cell motility, which was suppressed by ACTA2 shRNA overexpression in MDA-MB231 HER2 and 4T1 mammary carcinoma cells. The number of lung metastatic nodules was significantly decreased in ACTA2 knockdown mice. Taken together, these results demonstrated that induction of ACTA2 by EGFR and HER2 dimerization was regulated through a JAK2/STAT1 signaling pathway, and aberrant ACTA2 expression accelerated the invasiveness and metastasis of breast cancer cells.

Enhancement of breast cancer cell radiosensitivity by knockdown of HER-2 and TOP2A

Objective To study the individual and combined effects of HER-2 and TOP2A on the radiosensitivity of breast cancer SK-Br-3 cells, and to provide a basis for clinical research. Methods To knock down the expression of HER-2 and TOP2A, the recombinant plasmids expressing HER-2 siRNA or/and TOP2A siRNA were constructed and used to transfect SK-Br-3 cells using Lipofectamine 2000. Western blot was used to evaluate the knockdown efficiency two days later. Flow cytometry and MTT assay were used to evaluate apoptosis and proliferation in cells exposed to radiation, respectively. The expression of apoptosis-and proliferation-related proteins, consisting of caspase-3, Bcl-2, and Ki-67, was determined. The colony-formation assay was used to measure radiosensitivity. Results The breast cancer SK-Br-3 cells with HER-2 or TOP2A knockdown had a higher apoptosis rate and a lower proliferation rate after exposure to radiation. The apoptotic marker, activated caspase-3, had elevated expression, while the anti-apoptotic protein Bcl-2 and the proliferation marker Ki-67 had reduced expression. Knockdown of both HER-2 and TOP2A further promoted apoptosis and inhibited proliferation and colony formation, indicating a synergistic effect of HER-2 and TOP2A. Conclusions Knockdown of HER-2 and TOP2A expression elevates the radiosensitivity and apoptosis rate, and reduces the proliferation rate and colony-formation rate in the breast cancer SK-Br-3 cells. Moreover, there is a synergistic effect between HER-2 and TOP2A. The mechanism is probably related to the proliferation-related protein Ki-67 and the apoptosis pathway involving caspase-3 and Bcl-2. Key words: HER-2 gene; TOP2A gene; SK-Br-3 cell line; Radiosensitivity

HER2 induces cell proliferation and invasion of non-small-cell lung cancer by upregulating COX-2 expression via MEK/ERK signaling pathway.

HER2 positivity has been well studied in various cancers, but its importance in non-small-cell lung cancer (NSCLC) is still being explored. In this study, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to detect HER2 and COX-2 expression in NSCLC tissues. Then, pcDNA3.1-HER2 was used to overexpress HER2, while HER2 siRNA and COX-2 siRNA were used to silence HER2 and COX-2 expression. MTT assay and invasion assay were used to detect the effects of HER2 on cell proliferation and invasion. Our study revealed that HER2 and COX-2 expression were upregulated in NSCLC tissues and HER2 exhibited a significant positive correlation with the levels of COX-2 expression. Overexpression of HER2 evidently elevated COX-2 expression, while silencing of HER2 evidently decreased COX-2 expression. Furthermore, overexpressed HER2 induced the ERK phosphorylation, and this was abolished by the treatment with U0126, a pharmacological inhibitor of MEK, an upstream kinase of ERK. HER2-induced expression and promoter activity of COX-2 were also suppressed by U0126, suggesting that the MEK/ERK signaling pathway regulates COX-2 expression. In addition, HER2 induced activation of AKT signaling pathway, which was reversed by pretreatment with U0126 and COX-2 siRNA. MTT and invasion assays revealed that HER2 induced cell proliferation and invasion that were reversed by pretreatment with U0126 and COX-2 siRNA. In this study, our results demonstrated for the first time that HER2 elevated COX-2 expression through the activation of MEK/ERK pathway, which subsequently induced cell proliferation and invasion via AKT pathway in NSCLC tissues.

Therapeutic siRNA for drug-resistant HER2-positive breast cancer.

HER2 is overexpressed in about 20% of breast cancers and contributes to poor prognosis. Unfortunately, a large fraction of patients have primary or acquired resistance to the HER2-targeted therapy trastuzumab, thus a multi-drug combination is utilized in the clinic, putting significant burden on patients. We systematically identified an optimal HER2 siRNA from 76 potential sequences and demonstrated its utility in overcoming intrinsic and acquired resistance to trastuzumab and lapatinib in 18 HER2-positive cancer cell lines. We provided evidence that the drug-resistant cancer maintains dependence on HER2 for survival. Importantly, cell lines did not readily develop resistance following extended treatment with HER2 siRNA. Using our recently developed nanoparticle platform, systemic delivery of HER2 siRNA to trastuzumab-resistant tumors resulted in significant growth inhibition. Moreover, the optimal HER2 siRNA could also silence an exon 16 skipped HER2 splice variant reported to be highly oncogenic and linked to trastuzumab resistance.

SERPINA1 is a direct estrogen receptor target gene and a predictor of survival in breast cancer patients.

Of all breast cancer patients, about 70% are ER+ and 10% are ER+/HER2+. The ER+/HER2+ patients have a worse outcome compared to ER+/HER2- patients. Currently there is a lack of effective prognosis biomarkers for the prediction of outcome in ER+/HER2+ patients. Genome-wide differences in ER binding between the endocrine-responsive and endocrine-resistant cells were discovered using ChIP-seq, and combined with gene expression microarray data to identify direct ER target genes. These genes were correlated to survival outcome using publicly available breast cancer patient cohorts. We found the expression of the gene SERPINA1 to have a significant predictive value for the overall survival (OS) of ER+ patients in the TCGA cohort, and validated this finding in the Curtis cohort. SERPINA1 also has a significant predictive value for the OS of ER+/HER2+ patients in the TCGA cohort, with validation in the Bild cohort. The expression of SERPINA1 can be suppressed by fulvestrant and HER2 siRNA. Our results indicate that ER is constitutively activated, resulting in an E2-independent ER binding to the SERPINA1 gene and upregulation of SERPINA1 expression. Importantly, results of survival correlation suggests that high expression of SERPINA1 could be predictive for a better clinical outcome of ER+ and ER+/HER2+ patients.

Abstract B140: Positron emission tomography imaging of HER2 expression and pharmacodynamic response to HSP90 inhibition with the next-generation ZHER2:2891 Affibody molecule [18F]GE-226.

Abstract Accurate assessment of HER2 status remains a clinical challenge, with up to 20% of patients being potentially withdrawn from therapy or exposed to unnecessary toxicity. Non-invasive imaging is widely seen as a viable alternative to current methods, in particular in the setting of locoregional and distant recurrences not amenable to biopsy. A next-generation HER2-targeting Affibody-based radiotracer has been developed, [18F]GE-226, with enhanced pharmacokinetic characteristics and improved properties for large-scale and GMP grade synthesis. Kinetic modeling gave insights into Affibody-HER2 interactions. Intrinsic affinity to HER2 (KD = 76 pM) resulted in 11 to 67-fold higher [18F]GE-226 uptake in ten HER2 positive versus negative cell lines in vitro independent of lineage. Uptake correlated with HER2 protein expression but was independent of presence of other targets like EGFR. Blocking with [19F]GE-226 and HER2 siRNA treatment reduced uptake by 96.8 ± 2.6% and 81.7 ± 9.2%, respectively. Uptake in HER2 positive xenografts was rapid with steady state net irreversible binding kinetics making possible the distinction of HER2 negative (MCF7 (n = 6) and MCF7-p95HER2 (n = 3): NUV60 (normalized uptake value at 60 min; %ID/mL) 6.1 ± 0.7; Ki (irreversible uptake rate; mL/cm3/min) 0.0069 ± 0.0014) from HER2 positive tumors (NUV60 and Ki: MCF7-HER2, 10.9 ± 1.5 and 0.015 ± 0.0035; MDA-MB-361, 18.2 ± 3.4 and 0.025 ± 0.0052; SKOV-3, 18.7 ± 2.4 and 0.036 ± 0.0065; all n = 6) within 1 h. Tumor uptake correlated with HER2 expression determined by ELISA (r2=0.78). Specificity was further determined by comparing tumor localization of a fluorescently labeled tracer analogue with DAKO HercepTest. Affibody signal co-localized with HER2 expression at the cellular level independent of spatial heterogeneity. Tracer binding was not influenced by short-term or continuous exposure to trastuzumab in SKOV-3 xenografts (n=6) in keeping with differential epitope binding. Inhibition of the chaperone HSP90– of which HER2 is a client protein– by the therapeutic development candidate NVP-AUY922 caused dose-dependent HER2 degradation and consequently reduced tracer uptake in SKOV-3 cells in vitro and xenografts in vivo (area under the curve, AUC0-60: 618.4±90.1 and 446.7±42.8 %ID/mL*min for vehicle (n=4) and drug (n=5), respectively; P=0.043). In conclusion, [18F]GE-226 differentiates HER2 negative from HER2 expressing tumors. The tracer has potential utility for HER2 detection, irrespective of prior trastuzumab treatment and to monitor response to HSP90 inhibition. Lineage-independence of these results extends application beyond breast cancer. Due to the specific annotation to HER2, enhanced pharmacokinetic properties and completion of initial preclinical toxicology testing, [18F]GE-226 is now transitioning into clinical development. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B140. Citation Format: Sebastian Trousil, Susan Hoppmann, Quang-Dé Nguyen, Maciej Kaliszczak, Giampaolo Tomasi, Peter Iveson, Duncan Hiscock, Eric O. Aboagye. Positron emission tomography imaging of HER2 expression and pharmacodynamic response to HSP90 inhibition with the next-generation ZHER2:2891 Affibody molecule [18F]GE-226. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B140.

HER2 mediates epidermal growth factor-induced down-regulation of E-cadherin in human ovarian cancer cells

Overexpression of HER2 is correlated with a poor prognosis in many types of human cancers. Due to the interaction between HER2 and other ErbB receptors, HER2 is implicated in the EGF family of ligands-regulated tumor progression. In ovarian cancer, although the relationships between HER2 amplification and patient prognosis remain controversial, the underlying molecular mechanisms of HER2-mediated tumor progression are not fully understood. Our previous studies demonstrated that EGF induces ovarian cancer cell invasion by down-regulating E-cadherin expression through the up-regulation of its transcriptional repressors, Snail and Slug. It has been shown that overexpression of HER2 down-regulates E-cadherin expression in human mammary epithelial cells. However, whether HER2 mediates EGF-induced down-regulation of E-cadherin remains unknown. In this study, we examined the potential role of HER2 in EGF-induced down-regulation of E-cadherin and increased cell invasion. We show that EGF treatment induces the interaction of EGFR with HER2 and increases the activation of HER2 in human ovarian cancer cells; we also show that these effects are diminished by knockdown of EGFR. Importantly, treatment with HER2-specific tyrosine kinase inhibitor, AG825, and HER2 siRNA diminished the up-regulation of Snail and Slug as well as the down-regulation of E-cadherin by EGF. Finally, we also show that EGF-induced cell invasion was attenuated by treatment with HER2 siRNA. This study demonstrates an important role for HER2 in mediating the effects of EGF on Snail, Slug and E-cadherin expression as well as invasiveness in human ovarian cancer cells.

Different mechanisms for resistance to trastuzumab versus lapatinib in HER2-positive breast cancers--role of estrogen receptor and HER2 reactivation.

IntroductionThe human epidermal growth factor receptor 2 (HER2)-targeted therapies trastuzumab (T) and lapatinib (L) show high efficacy in patients with HER2-positive breast cancer, but resistance is prevalent. Here we investigate resistance mechanisms to each drug alone, or to their combination using a large panel of HER2-positive cell lines made resistant to these drugs.MethodsResponse to L + T treatment was characterized in a panel of 13 HER2-positive cell lines to identify lines that were de novo resistant. Acquired resistant lines were then established by long-term exposure to increasing drug concentrations. Levels and activity of HER2 and estrogen receptor (ER) pathways were determined by qRT-PCR, immunohistochemistry, and immunoblotting assays. Cell growth, proliferation, and apoptosis in parental cells and resistant derivatives were assessed in response to inhibition of HER or ER pathways, either pharmacologically (L, T, L + T, or fulvestrant) or by using siRNAs. Efficacy of combined endocrine and anti-HER2 therapies was studied in vivo using UACC-812 xenografts.ResultsER or its downstream products increased in four out of the five ER+/HER2+ lines, and was evident in one of the two intrinsically resistant lines. In UACC-812 and BT474 parental and resistant derivatives, HER2 inhibition by T reactivated HER network activity to promote resistance. T-resistant lines remained sensitive to HER2 inhibition by either L or HER2 siRNA. With more complete HER2 blockade, resistance to L-containing regimens required the activation of a redundant survival pathway, ER, which was up-regulated and promoted survival via various Bcl2 family members. These L- and L + T-resistant lines were responsive to fulvestrant and to ER siRNA. However, after prolonged treatment with L, but not L + T, BT474 cells switched from depending on ER as a survival pathway, to relying again on the HER network (increased HER2, HER3, and receptor ligands) to overcome L's effects. The combination of endocrine and L + T HER2-targeted therapies achieved complete tumor regression and prevented development of resistance in UACC-812 xenografts.ConclusionsCombined L + T treatment provides a more complete and stable inhibition of the HER network. With sustained HER2 inhibition, ER functions as a key escape/survival pathway in ER-positive/HER2-positive cells. Complete blockade of the HER network, together with ER inhibition, may provide optimal therapy in selected patients.

Abstract 5126: Development of a high throughput quantitative phosphoproteomic method to study trastuzumab resistance

Abstract Her2 is a receptor tyrosine kinase that is overexpressed in approximately 20-30% of human breast cancers and affects clinical prognosis and outcome of these cancers. Treatment of Her2-positive breast cancer with the monoclonal antibody, trastuzumab, has improved the outcomes and prognosis for patients with this breast cancer subtype. However, development of resistance to trastuzumab is a major clinical problem in metastatic Her2-positive breast cancer. Many of the known mechanisms of trastuzumab resistance cause changes in protein phosphorylation patterns and therefore we have employed quantitative phosphoproteomics to further study trastuzumab resistance. Quantitative phosphoproteomics is a powerful method to comparatively identify phosphorylated proteins between different samples. Using electrospray tandem-mass spectrometry coupled with immunoaffinity purification and titanium dioxide (TiO2) phosphoenrichment, we wanted to identify differentially phosphorylated proteins in a pair of trastuzumab sensitive and resistant cells. We used stable isotope labeling of amino acids in cell culture (SILAC) to obtain quantitative information on the proteins identified by mass spectrometry. We have obtained quantitative data on two trastuzumab sensitive and resistant pairs of Her2 overexpressing human breast cancer cell lines (BT474 and SKBR3). 275 proteins were identified in the phosphoenriched fraction from the SKBR3 pair with 83 proteins reporting a ratio. 769 proteins were identified in the phosphoenriched fraction from the BT474 pair with 683 proteins reporting a ratio. Treatment of the trastuzumab resistant cells with Her2 siRNA drastically resulted in cell death indicating the sustained dependence of these cells on Her2 despite the resistance to Her2 targeted therapy. RNAi experiments, in combination with trastuzumab exposure, of candidate proteins expressing an increase in phosphorylation will be tested further to determine if trastuzumab resistance can be reversed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5126. doi:10.1158/1538-7445.AM2011-5126

Nudix‐type motif 2 in human breast carcinoma: A potent prognostic factor associated with cell proliferation

Nudix-type motif 2 (NUDT2) hydrolyzes diadenosine 5',5'''-p1,p4-tetraphosphate (Ap4A) associated with various cellular functions. Previous studies demonstrated its regulation through estrogens, suggesting possible importance of NUDT2 in breast carcinoma. NUDT2, however, has not been examined in malignant tissues. Therefore, we examined its expression and functions in breast carcinoma. Immunohistochemistry for NUDT2 was examined by invasive ductal carcinoma (IDC: n = 145) and pure ductal carcinoma in situ (DCIS: n = 82), and NUDT2 mRNA was examined by real-time PCR in 9 DCIS, 19 IDC and 6 non-neoplastic breast tissues. We also used T47D breast carcinoma cells in in vitro studies. NUDT2 immunoreactivity was detected in 78% of DCIS and 63% of IDC, and NUDT2 mRNA level was significantly higher in DCIS or IDC than non-neoplastic breast. NUDT2 status was significantly correlated with Van Nuys classification, HER2 or Ki-67 in DCIS, and with stage, lymph node metastasis, histological grade or HER2 in IDC. NUDT2 status was significantly associated with adverse clinical outcome of IDC patients and proved an independent prognostic factor. Results of transfection experiments demonstrated that proliferation activity of T47D cells was significantly associated with NUDT2 expression level according to the treatment of estradiol and/or tamoxifen. NUDT2 expression was significantly decreased by estradiol, and it was also significantly decreased in T47D cells transfected with HER2 siRNA. These findings suggest that NUDT2 is an estrogen-repressed gene and is also induced by HER2 pathways in breast carcinoma cells. NUDT2 promotes proliferation of breast carcinoma cells and is a potent prognostic factor in human breast carcinomas.

Increase of the therapeutic effect by treating nasopharyngeal tumor with combination of HER-2 siRNA and paclitaxel

Therapeutic agents targeting HER-2/neu have been intensively addressed over the past decades. Previously, we reported that HER-2 synthetic small interfering RNA (HER-2 siRNA) could suppress the growth of human nasopharyngeal KB tumor xenografts by intratumoral injection with lipid-based nanoparticles; however, complete regression of the tumor was not achieved. In this study, we investigated antitumor activity by RNA interference in combination with paclitaxel (PTX) for KB cells using HER-2 siRNA and HER-2 short hairpin RNA-expressing plasmid DNA (HER-2 shRNA pDNA). Suppression of HER-2 expression by siRNA or shRNA pDNA caused significant reduction of proliferation by inducing apoptosis and enhancing the sensitivity for PTX in HER-2 positive KB cells. Interestingly, an HER-2 antibody trastuzumab could not increase the antitumor effect by PTX in KB xenografts. Combination therapy by intratumoral injection of HER-2 siRNA or HER-2 shRNA pDNA with PTX significantly inhibited the tumor growth of xenografts compared with each therapy used individually. In particular, HER-2 shRNA pDNA plus PTX largely extended the mean survival days compared with HER-2 siRNA plus PTX. Collectively, these findings suggest that HER-2 shRNA-based combined therapy with PTX could be a novel strategy to inhibit the progression of HER-2-positive cancer.