Lupu, Ruth

Abstract About 25% of breast carcinomas are characterized by over-expression and/or amplification of the HER2 receptor, one of four members of the HER family of receptor tyrosine kinases. The strong correlation between HER2 levels/activity with more aggressive breast cancer disease, poor prognosis as well as resistance to chemo- and endocrine therapies made it a preferred target for anti-cancer therapy. However, current treatment strategies are only partially effective and the majority of breast cancer patients who initially respond favorably rapidly develop resistance to treatments for still not fully understood reasons. Thus, novel strategies/agents are in need. Structural analyses revealed that sub-domain III in the extracellular domain (ECD) of the HER family members is responsible for dimerization. We hypothesized that disrupting the dimerization loop in the HER2-ECD sub-domain III would ultimately convert HER2 to a non-functional receptor with diminished transforming capacity. To this end, we generated a series of HER2-ECD deletion mutants located in sub-domain III and assessed their oncogenic potential compared to the HER2-wild type (WT) after their expression in MCF10A cells. Importantly, a small deletion (16 amino acids) of the HER2 extracellular domain (named HER2Δ6) abolished its homo- and hetero-dimerization and profoundly affected HER2-catalyzed activation of the HER network. Moreover, this mutant was not able to transform MCF10 cells as it failed to promote anchorage-independent growth and interfered with the activation/Tyr phosphorylation of HER1, HER2 and HER3. Compared to HER2-WT-expressing cells, the HER2α6 mutant proved to be even more effective in inhibiting the oncogenic properties of the receptor than the current drugs of choice such as Trastuzumab and Pertuzumab alone or in combination. In addition, while expression of HER2-WT conferred resistance of MCF10A cells to Paclitaxel, the HER2Δ6 variant failed to do so. To determine the molecular mechanisms underlying this behavior, we assessed the mutant and WT expressing cells lines morphologically and biochemically and demonstrated that the HER2Δ6 is absent from the plasma membrane (PM) in MCF10A cells. Interestingly, we found that the mutant receptor displayed an intracellular trafficking defect and was trapped in the endoplasmic reticulum (ER). Our results reveal that the HER2-ECD bears an essential “activating” region that is indispensable for HER2-mediated oncogenic transformation. Targeting and eliminating this “activating” element in HER2 seems to provide a strong innovative approach for developing a valuable novel anti-HER2 therapeutic drug that would specifically benefit patients with HER2 positive tumors resistant to current therapies. Citation Format: Barbara Schroeder, Ghiara Lugo, Javier Menendez, Ingrid Espinoza, Ruth Lupu. Identification of a key region in the HER2 subdomain III required for transformation capability. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 133. doi:10.1158/1538-7445.AM2015-133

Abstract Heregulin (HRG)s are high-affinity combinatorial ligands for the HER family of tyrosine kinase receptors. HRG induces heterodimerization and cross-talk between members of the HER tyrosine kinase receptor family. HRG interaction with HER3 induces heterodimerization between HER3 and other HER receptors, including epidermal growth factor receptor (EGFR) and HER2, resulting in cross-talk-induced tyrosine phosphorylation. Several studies have revealed that HRG is expressed in about 40% of invasive breast carcinomas, many of which are triple negative breast carcinomas. We have previously demonstrated that HRG expression induces tumorigenesis and metastasis of MCF-7 cells. We tested the effect of HRG on non-committed MCF10A cells. MCF-10A cell line is an immortalized, non-transformed epithelial cell line derived from human fibrocystic mammary tissue. These cells lack the ability to form tumors in nude mice and the ability to grow in anchorage-independent assays. We found that forced expression of HRG in MCF10A induced cellular transformation, while the control MCF10A/Vector cells did not growth. MCF10A/HRG cells express constitutive phosphorylation of HER3 and induction of the signaling cascade. HER3 phosphorylation occurs as a result of HRG induction of HER3 heterodimerization with EGFR in an autocrine manner. Lapatinib, a dual tyrosine kinase inhibitor which interrupts the HER2 and EGFR pathways, blocked HER3 phosphorylation and the resulted signaling in MCF10A/HRG cells and prevented their anchorage-independent growth demonstrating that HER3 phosphorylation is responsible, at least in part, for the transformation of MCF10A/HRG cells. This study provides an alternate targeting prospective for breast carcinomas that express HER3 and HRG by targeting the autocrine-loop (HRG/HER3) and thus preventing HRG from binding to HER3, disrupting the possible receptor heterodimerization, and leading to blockage of the proliferative signals and promoting inhibition of growth. Citation Format: Ruth Lupu, Ashwani Khurana, Ghiara Lugo, Anatilde Gonzalez Guerrico. Heregulin induces transformation of mammary epithelial cells via HER3 activation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3506. doi:10.1158/1538-7445.AM2014-3506

Abstract Increased de novo lipogenesis due to enhanced expression of several lipogenic enzymes has been found in many types of human cancers. Fatty acid synthase (FASN), the key enzyme in the de novo lipogenesis pathway, is one of the most commonly over-expressed lipogenic enzymes. Studies in the past decade have recognized FASN overexpression as a molecular marker for poor prognosis and malignant phenotype of many cancers. Tumor-associated FASN, by conferring growth and survival advantages rather than functioning as an anabolic energy-storage pathway, has also been suggested to play an active part in the development, maintenance, and metastatic progression of human cancers. More recently, FASN has been implicated in contributing to cellular resistance to several anticancer treatments. A variety of agents have been developed to target lipogenic enzymes and the key regulators involved in lipid metabolism in cancer cell for therapeutic purposes. The development of several FASN inhibitors has been reported from both academic labs and industries. When used in in vitro, xenograft and genetically induced mouse model studies, these inhibitors have supported FASN as an excellent target. A new generation of FASN inhibitors was developed at 3-V Biosciences that are highly specific, reversible inhibitors of FASN. One compound in this series, TVB-2640, is orally bioavailable and has progressed into Phase 1 clinical studies. The effect of two anti-FASN drugs in this series, TVB-3150 and TVB-3199 were tested for their effect on breast cancer cells. We demonstrated that the EC50 is between 9-50 nM, depending on the drug and the tested cell line. We then demonstrated that the drugs inhibited the anchorage-dependent and -independent growth of FASN expressing cells in a dose dependent manner. The apparent mechanism by which the FASN inhibitors promote inhibition of growth is by inducing apoptotic cell death in a time- and dose-dependent manner that involves regulation of apoptotic and pro-apoptotic proteins. Furthermore, the combination of the anti-FASN drugs with small molecule inhibitors of the antiapoptotic proteins Bcl-2 and Bcl-xL significantly increased the apoptotic effect in a synergistic manner compared to either of the synthetic inhibitors alone. In vivo studies demonstrate tumor growth inhibition without toxicity. Clinical development of a first-in-class, orally active, potent, and reversible FASN inhibitor as a novel cancer therapeutic is ongoing. Citation Format: Ruth Lupu, Anatilde Gonzalez Guerrico, Ashwani Khurana, Timothy Heuer, George Kemble, Chandra Mohan KVP. Small-molecule FASN inhibitors promote growth inhibition growth and apoptosis of breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2713. doi:10.1158/1538-7445.AM2014-2713

Abstract The HER2 receptor is over-expressed in about 25% of breast carcinomas and correlates with more aggressive breast cancer disease, poor prognosis as well as resistance to chemo- and endocrine therapies. The strong correlation between HER2 levels/activity and the malignancy of the disease made it a preferred target for anti-cancer therapy. For example, Trastuzumab, which targets HER2 homo-dimerization and Pertuzumab, which interferes with HER2 hetero-dimerization, are in clinical use. Unfortunately, Trastuzumab monotherapy is only partially effective and the majority of breast cancer patients who initially respond to Trastuzumab rapidly develop resistance to the drug. Thus, novel strategies/agents are in need, especially drugs that prevent hetero-dimerization with other HER family members. Structural analyses revealed that sub-domain III in the extracellular domain (ECD) of the HER family members is responsible for dimerization. Therefore, we hypothesized that disabling the dimerization loop in the HER2-ECD sub-domain III would ultimately convert HER2 to a non-functional receptor. Therefore, we introduced a series of deletions in the HER2-ECD sub-domain III and determined their oncogenic properties compared to HER2wt expressing cells. Importantly, a small deletion (16 amino acids) of the HER2 extracellular domain (named HER2Δ6) abolished its homo- and hetero-dimerization and profoundly affected HER2-catalyzed activation of the HER network, both in the context of HER2 over-expression and ligand-induced trans-activation of HER2. Expression of the HER2Δ6 variant failed to promote anchorage-independent growth and interfered with the activation/Tyr phosphorylation of HER1, HER2 and HER3. Moreover, this mutant failed to promote resistance to Paclitaxel treatment in HER2-overexpressing breast cancer cells. To determine the molecular mechanisms underlying this behavior, we assessed the mutant and wt expressing cells lines morphologically and biochemically and demonstrated that the HER2Δ6 is absent from the plasma membrane (PM), most likely due to a intracellular trafficking defect that mistargets the receptor to or traps it in an endomembrane compartment. Compared to HER2wt-expressing cells, the HER2Δ6 mutant proves to be even more effective in inhibiting the oncogenic properties of the receptor than the current drugs of choice such as Trastuzumab, Pertuzumab and Cetuximab alone or in combination as measured by anchorage-independent growth. These findings reveal that the HER2-ECD bears an essential "activating" region that is indispensable for HER2 homo-and heterodimerization. Elimination of this "activating" element in HER2 seems to recapitulate and greatly improve the combined actions of Trastuzumab and Pertuzumab. These findings offer a strong rationale for developing this peptide sequence into a valuable anti-HER2 therapeutic drug. Citation Format: Barbara Schroeder, Menendez Javier, Espinoza Ingrid, Lupu Ruth. Blocking a key region in the HER2 subdomain III inhibits the HER2-network in patients with resistance to HER2-targeted therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-08.

Abstract Overcoming drug resistance, emerging either on recurring cancer or metastasis, is a major challenge of cancer treatments. The combination of anti-angiogenic agents with chemotherapeutic ones offers a promising therapeutic approach. Such combination can be achieved exploiting the multivalency of polymer therapeutics. We have recently showed that polymer conjugation of paclitaxel (PTX), a potent cytotoxic and anti-angiogenic drug, improved its pharmacokinetic profile. We hypothesized that actively targeting PTX to αvβ3-integrin, presents an attractive therapeutic strategy for breast cancer. Interestingly, overexpression of αvβ3-integrin, occurring on tumor endothelial and some epithelial cells during tumor growth, invasion, and metastasis, was found to correlate with PTX-resistance of breast cancer cells. We designed and synthesized a novel polyglutamic acid (PGA)-PTX-E-[c(RGDfK)2] nano-sized conjugate. Polymer conjugation converted PTX to a water-soluble macromolecule, which passively targeted the tumor tissue exploiting the enhanced permeability and retention (EPR) effect. The E-[c(RGDfK)2] was utilized as an additional active targeting moiety to αvβ3 integrin. PGA is enzymatically-degradable by cathepsin B, leading to PTX release. PGA-PTX-E-[c(RGDfK)2] displayed a potent anti-angiogenic activity, determined by several well-established in vitro assays. Preferential tumor accumulation of the RGD-bearing conjugate in orthotopic mammary tumors inoculated in mice, lead to enhanced antitumor efficacy and a marked decrease in toxicity compared with free PTX. We found that metastasis establishment was dependent on αvβ3-integrin expression as determined in vitro and ex vivo. PGA-PTX-E-[c(RGDfK)2] conjugate inhibited metastatic growth in an experimental breast cancer metastases model in mice. Taken together, inclusion of an active targeting moiety to integrin expressing-cells has the potential to decrease breast cancer metastases establishment by displaying an anti-angiogenic and anticancer activity. Citation Format: Anat Eldar-Boock, Dikla Ben-Shushan, Joaquin Sanchis, Ruth Lupu, Maria J. Vicent, Ronit Satchi-Fainaro. Preventing breast cancer metastases with an anti-angiogenic and anticancer RGD-bearing nanomedicine. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-196. doi:10.1158/1538-7445.AM2014-LB-196

Abstract Fatty acid synthase (FASN), the key enzyme in de novo lipogenesis, is significantly upregulated and activated in many carcinomas, including breast cancer. Pharmacological inhibition of FASN induces apoptosis of FASN expressing cancer cells. However, the mechanism is still unclear. Inhibition of FASN in breast cancer cells induces a dose dependent increase in apoptotic cell death with a concomitant upregulation of the pro-apoptotic BH3-only proteins Noxa, Bim and Puma (mRNA and protein). Blockage of the BH3-only protein expression using specific small interfering ribonucleic acid (siRNA), significantly diminishes the apoptotic effect induced by the inhibition of FASN. Moreover, addition of palmitate, the end product of FASN, protects the cells from the proapoptotic effects of FASN inhibition by suppressing expression of Noxa, Bim and Puma. These data indicate that Noxa, Bim and Puma are essential for the apoptotic effect induced by the inhibition of FASN. Combination therapeutic regimens have received growing attention for the possibility of higher efficacy with reduced toxicity. Thus, we investigated the combinatorial effect of pharmacological inhibition of FASN and Bcl-2/Bcl-xL. While a small molecule Bcl-2/Bcl-xL inhibitor alone did not induce apoptosis, co-treatment of the small molecule Bcl-2/Bcl-xL inhibitor with a synthetic FASN inhibitor significantly surpassed the apoptotic effect of the synthetic FASN inhibitor alone. Accordingly, combined treatment of a FASN inhibitors and Bcl-2/Bcl-xL antagonists represents a new rational combination that merits further consideration in FASN overexpressing tumors. Citation Format: Chandra Mohan Kurapaty Venkatapoorna, Ingrid Espinoza, Scott H Kaufmann, Ruth Lupu. Pharmacological inhibition of fatty acid synthase regulates BH3-only proteins and sensitizes breast cancer cells to a small molecule Bcl-2/Bcl-xL inhibitor to induce apoptosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1737. doi:10.1158/1538-7445.AM2013-1737 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.