Conjugateswith an active participation of somatostatin receptors in cellular uptake. Similar cytotoxic activity was found in a normal cell line (IC 50 = 45 + 2.6 µM in CHO cells), which can be attributed to a similar level of expression of somatostatin subtype-2 receptor. These studies provide new insights into the effect of receptor-binding peptide conjugation on the activity of metal-based anticancer drugs, and demonstrate the potential of such hybrid compounds to target tumor cells specifically.

Blocking the enzyme Fatty Acid Synthase (FASN) leads to apoptosis of HER2-positive breast carcinoma cells. The hypothesis is that blocking FASN, in combination with anti-HER2 signaling agents, would be an effective antitumor strategy in preclinical HER2+ breast cancer models of trastuzumab and lapatinib resistance. We developed and molecularly characterized in vitro HER2+ models of resistance to trastuzumab (SKTR), lapatinib (SKLR) and both (SKLTR). The cellular interactions of combining anti-FASN polyphenolic compounds (EGCG and the synthetic G28UCM) with anti-HER2 signaling drugs (trastuzumab plus pertuzumab and temsirolimus) were analyzed. Tumor growth inhibition after treatment with EGCG, pertuzumab, temsirolimus or the combination was evaluated in two in vivo orthoxenopatients: one derived from a HER2+ patient and another from a patient who relapsed on trastuzumab and lapatinib-based therapy. SKTR, SKLR and SKLTR showed hyperactivation of EGFR and p-ERK1/2 and PI3KCA mutations. Dual-resistant cells (SKLTR) also showed hyperactivation of HER4 and recovered levels of p-AKT compared with mono-resistant cells. mTOR, p-mTOR and FASN expression remained stable in SKTR, SKLR and SKLTR. In vitro, anti-FASN compounds plus pertuzumab showed synergistic interactions in lapatinib- and dual- resistant cells and improved the results of pertuzumab plus trastuzumab co-treatment. FASN inhibitors combined with temsirolimus displayed the strongest synergistic interactions in resistant cells. In vivo, both orthoxenopatients showed strong response to the antitumor activity of the combination of EGCG with pertuzumab or temsirolimus, without signs of toxicity. We showed that the simultaneous blockade of FASN and HER2 pathways is effective in cells and in breast cancer models refractory to anti-HER2 therapies.

Abstract. The deregulation of the epidermal growth factor receptor (EGFR) pathway plays a major role in the pathogenesis of prostate cancer (PCa). However, therapies targeting EGFR have demonstrated limited effectiveness in PCa. A potential mechanism to overcome EGFR blockade in cancer cells is the autocrine activation of alternative receptors of the human EGFR (HER) family through the overexpression of the HER receptors and ligands. In the present study, we were interested in analyzing if this intrinsic resistance mechanism might contribute to the inefficacy of EGFR inhibitors in PCa. To this end, we selected two androgen-independent human prostate carcinoma cell lines (DU145 and PC3) and established DU145 erlotinib-resistant cells (DUErR). Cells were treated with three EGFR inhibitors (cetuximab, gefinitib and erlotinib) and the sensitivity to each treatment was assessed. The gene expression of the four EGFR/HER receptors and seven ligands of the HER family was analyzed by real-time PCR prior to and after each treatment. The receptors expression and activation were further characterized by flow cytometry and western blot analysis. EGFR inhibition rapidly induced enhanced gene expression of the EGF, betacellulin and neuregulin-1 ligands along with HER2, HER3 and HER4 receptors in the DU145 cells. In contrast, slight changes were observed in the PC3 cells, which are defective in the phosphatase and tensin homolog (PTEN) tumor suppressor gene. In the erlotinib-resistant DUErR cells, the expression of HER2 and HER3 was increased at mRNA and protein levels together with neuregulin-1, leading to enhanced HER3 phosphorylation and the activation of the downstream PI3K/Akt survival pathway. HER3 blockage by a monoclonal antibody restored the cytostatic activity of erlotinib in DUErR cells. Our results confirm that the overexpression and autocrine activation of HER3 play a key role in mediating the resistance to EGFR inhibitors in androgen-independent PCa cells.

&These two authors contributed equally to this work. ABSTRACTA straightforward methodology for the synthesis of conjugates between a cytotoxic organometallic ruthenium(II) complex and amino-and guanidinoglycosides, as potential RNA-targeted anticancer compounds, is described. Under microwave irradiation, the imidazole ligand incorporated on the aminoglycoside moiety (neamine or neomycin) was found to replace one triphenylphosphine ligand from the ruthenium precursor [(η 6 -p-cym)RuCl(PPh 3 ) 2 ] + , allowing the assembly of the target conjugates. The guanidinylated analogue was easily prepared from the neomycin-ruthenium conjugate by reaction with N,N'-di-Boc-N"-triflylguanidine, a powerful guanidinylating reagent that was compatible with the integrity of the metal complex. All conjugates were purified by semi-preparative HPLC and characterized by ESI and MALDI-TOF MS and NMR spectroscopy. The cytotoxicity of the compounds was tested in and DU-145 (prostate) human cancer cells, as well as in the normal HEK293 (Human Embryonic Kidney) cell line, revealing a dependence on the nature of the glycoside moiety and the type of cell (cancer or healthy). Indeed, neomycin-ruthenium conjugate (2) displayed moderate anti-proliferative activity in both cancer cell lines (IC 50 ≈ 80 µM), whereas that of the neamine conjugate (4) was inactive (IC 50 ≈ 200 µM).However, the guanidinylated analogue of the neomycin-ruthenium conjugate (3) required much lower concentrations than the parent conjugate for equal effect (IC 50 = 7.17 µM in DU-145 and IC 50 = 11.33 µM in MCF-7). Although the same ranking in anti-proliferative activity was found in the non-tumorigenic cell line (3 >> 2 > 4), IC 50 values indicate that aminoglycoside-containing conjugates are about 2-fold more cytotoxic in normal cells (e.g. IC 50 = 49.4 µM for 2) than in cancer cells, whereas an opposite tendency was found with the guanidinylated conjugate, since its cytotoxicity in the normal cell line (IC 50 = 12.75 µM for 3) was similar or even lower than that found in MCF-7 and DU-145 cancer cell lines, respectively. Cell uptake studies performed by ICP-MS with conjugates 2 and 3 revealed that guanidinylation of the neomycin moiety had a positive effect on accumulation (about 3-fold higher in DU-145 and 4-fold higher in HEK293), which correlates well with the higher anti-proliferative activity of 3.Interestingly, despite the slightly higher accumulation in the normal cell than in the cancer cell line (about 1.4-fold), guanidinoneomycin-ruthenium conjugate (3) was more cytotoxic to cancer cells (about 1.8-fold), whereas the opposite tendency applied for neomycin-ruthenium conjugate (2). Such differences in cytotoxic activity and cellular 3 accumulation between cancer and normal cells open the way to the creation of more selective, less toxic anticancer metallodrugs by conjugating cytotoxic metal-based complexes such as ruthenium(II) arene derivatives to guanidinoglycosides.

Introduction: Resistance to dual biological blockade of HER2 positive breast cancer arises as a novel therapeutic challenge with high clinical relevance. We have shown that inhibition of fatty acid synthase (FASN) has anticancer activity and enhances the effect of chemotherapy and anti-HER2 drugs in pre-clinical breast cancer models. Furthermore, our group has recently observed that inhibition of FASN can reverse resistance to anti-HER2 therapies. The development of FASN inhibitors has consequently appeared as a novel anti-target modality for treating cancer. However, the clinical use of FASN inhibitors, such as Cerulenin, C75 and Epigallocatechin 3-gallate (EGCG) is limited by anorexia and induced body weight loss or by its low in vivo potency and stability. We synthesized novel EGCG-related inhibitors to improve their use as anti-tumor agents. Within these, G28UCM was selected for its inhibitory effect of FASN activity and selective cytotoxicity in tumor cells. Recently, it has been reported that mTOR blockade acts synergistically with HER2 inhibition to induce cell death and tumor regression in resistant breast cancer models. Materials and Methods: We have developed long term HER2+/ FASN+ breast cancer cell lines (SKBr3) resistant to the HER2-monoclonal antibody Trastuzumab (SKTR), the EGFR/HER2-tyrosine kinase inhibitor Lapatinib (SKLR) or both (SKLTR). Once established, we have characterized these cells by studying a panel of EGF receptors signaling proteins with western blot analysis, changes in adherence to extracellular matrix proteins and invasion capacity with colorimetric assays. Using MTT assay, we have assessed the effect of the mTOR-inhibitor, Temsirolimus, and G28UCM on viability of parental and resistant cells. The isobologram method has been used to estimate the possible synergistic effect between both treatments. Results: Resistant cells maintained downstream HER2 pathway activation by stimulating the expression/activation of alternative EGF family receptors and/or those specific ligands. Moreover, these cells increased adherence to extracellular matrix proteins and invasion capacity. Different combination regiment of Temsirolimus with G28UCM displayed a strong synergistic effect in inducing cell death of both, parental and resistant HER2+ breast cancer cells. Conclusions: The inhibition of mTOR and FASN is a potential novel therapeutic strategy in dual resistant HER2 positive breast cancer. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-11-02.