Lonidamine causes inhibition of angiogenesis-related endothelial cell functions

Epigenetics as a strategic intervention for early diagnosis and combatting glycolyis-induced chemoresistance in gynecologic cancers

Prospective prediction from the Australian Institute of Health and Welfare (AIHW) showed a likely incidence of 1 in 23 women diagnosed with gynaecological malignancy, where the incidence of relapse with a drug-resistant clone poses a significant challenge in dealing with it even after initial treatment. Glucose metabolism has been exploited as a therapeutic target under anti-metabolomic study, but the non-specificity narrowed its applicability in cancer. Novel updates over epigenetics as a target in gynaecological cancer offer a rational idea of using this in the metabolic rewiring in mutated glycolytic flux-induced drug resistance. This review focuses on the application of epigenetic intervention at a diagnostic and therapeutic level to shift the current treatment paradigm of gynaecological cancers from reactive medicine to predictive, preventive, and personalised medicine. It presents the likely epigenetic targets that can be exploited potentially to prevent the therapeutic failure associated with glucose metabolism-induced chemotherapeutic drug resistance.

Effects of metabolic cancer therapy on tumor microenvironment

Targeting tumor metabolism for cancer therapy is an old strategy. In fact, historically the first effective cancer therapeutics were directed at nucleotide metabolism. The spectrum of metabolic drugs considered in cancer increases rapidly - clinical trials are in progress for agents directed at glycolysis, oxidative phosphorylation, glutaminolysis and several others. These pathways are essential for cancer cell proliferation and redox homeostasis, but are also required, to various degrees, in other cell types present in the tumor microenvironment, including immune cells, endothelial cells and fibroblasts. How metabolism-targeted treatments impact these tumor-associated cell types is not fully understood, even though their response may co-determine the overall effectivity of therapy. Indeed, the metabolic dependencies of stromal cells have been overlooked for a long time. Therefore, it is important that metabolic therapy is considered in the context of tumor microenvironment, as understanding the metabolic vulnerabilities of both cancer and stromal cells can guide new treatment concepts and help better understand treatment resistance. In this review we discuss recent findings covering the impact of metabolic interventions on cellular components of the tumor microenvironment and their implications for metabolic cancer therapy.

The lonidamine derivative H2-gamendazole reduces cyst formation in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a debilitating renal neoplastic disorder with limited treatment options. It is characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. We tested the effectiveness of the indazole carboxylic acid H2-gamendazole (H2-GMZ), a derivative of lonidamine, to inhibit these processes using in vitro and in vivo models of ADPKD. H2-GMZ was effective in rapidly blocking forskolin-induced, Cl--mediated short-circuit currents in human ADPKD cells, and it significantly inhibited both cAMP- and epidermal growth factor-induced proliferation of ADPKD cells. Western blot analysis of H2-GMZ-treated ADPKD cells showed decreased phosphorylated ERK and decreased hyperphosphorylated retinoblastoma levels. H2-GMZ treatment also decreased ErbB2, Akt, and cyclin-dependent kinase 4, consistent with inhibition of heat shock protein 90, and it decreased levels of the cystic fibrosis transmembrane conductance regulator Cl- channel protein. H2-GMZ-treated ADPKD cultures contained a higher proportion of smaller cells with fewer and smaller lamellipodia and decreased cytoplasmic actin staining, and they were unable to accomplish wound closure even at low H2-GMZ concentrations, consistent with an alteration in the actin cytoskeleton and decreased cell motility. Experiments using mouse metanephric organ cultures showed that H2-GMZ inhibited cAMP-stimulated cyst growth and enlargement. In vivo, H2-GMZ was effective in slowing postnatal cyst formation and kidney enlargement in the Pkd1flox/flox: Pkhd1-Cre mouse model. Thus, H2-GMZ treatment decreases Cl- secretion, cell proliferation, cell motility, and cyst growth. These properties, along with its reported low toxicity, suggest that H2-GMZ might be an attractive candidate for treatment of ADPKD.NEW & NOTEWORTHY Autosomal dominant polycystic kidney disease (ADPKD) is a renal neoplastic disorder characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. This study shows that the lonidamine derivative H2-GMZ inhibits Cl- secretion, cell proliferation, and cyst growth, suggesting that it might have therapeutic value for the treatment of ADPKD.

Endothelial Cell Glucose Metabolism and Angiogenesis

Angiogenesis, a process of new blood vessel formation from the pre-existing vascular bed, is a critical event in various physiological and pathological settings. Over the last few years, the role of endothelial cell (EC) metabolism in angiogenesis has received considerable attention. Accumulating studies suggest that ECs rely on aerobic glycolysis, rather than the oxidative phosphorylation pathway, to produce ATP during angiogenesis. To date, numerous critical regulators of glucose metabolism, fatty acid oxidation, and glutamine metabolism have been identified to modulate the EC angiogenic switch and pathological angiogenesis. The unique glycolytic feature of ECs is critical for cell proliferation, migration, and responses to environmental changes. In this review, we provide an overview of recent EC glucose metabolism studies, particularly glycolysis, in quiescent and angiogenic ECs. We also summarize and discuss potential therapeutic strategies that take advantage of EC metabolism. The elucidation of metabolic regulation and the precise underlying mechanisms could facilitate drug development targeting EC metabolism to treat angiogenesis-related diseases.

Potentiation of the Effect of Lonidamine by Quercetin in MCF-7 human breast cancer cells through downregulation of MMP-2/9 mRNA Expression

Combination therapies are becoming increasingly important to develop an effective treatment in cancer. Lonidamine is frequently used in cancer treatment, but it's often preferred to be used in combination with other drugs because of its side effects. In the present study, the efficacy of the combination of lonidamine with quercetin, a flavonoid of natural origin, on human MCF-7 breast cancer cells was evaluated. The results showed that the combined use of the compounds significantly increased cytotoxicity compared to administration alone (p<0.0001). In addition, while lonidamine induced a cell cycle arrest in the G2/M phase, administration of quercetin and its combination with lonidamine arrested the cell division at S point, indicating the synergistic strength of quercetin on cytotoxicity. The combination of quercetin and lonidamine significantly induced apoptosis of MCF-7 cells (p<0.0001) and increased caspase levels (p<0.0001). In this study, the combination of quercetin and lonidamine has been evaluated for the first time and the combination treatment decreased MMP-2/-9 mRNA expression more potently than the effects of the compounds alone. The results showed that lonidamine was more effective when combined with quercetin, and their combination may be a candidate for a novel strategy of treatment for breast cancer.

Clinicopathological and immunohistochemical evaluation of lonidamine-entrapped lipid-polymer hybrid nanoparticles in treatment of benign prostatic hyperplasia: An experimental rat model

Benign prostatic hyperplasia (BPH) is a progressive proliferative disease, the incidence of which is constantly increasing due to aging of population. In this research, a hexokinase-II enzyme inhibiting agent, lonidamine - the use of which is limited in BPH treatment due to high hepatic toxicity observed after three months of treatment - was selected as an active agent, based on its mechanism of action in treating BPH. The aim of this study was to evaluate in vivo therapeutic efficacy and hepatic toxicity of lipid-polymer hybrid nanoparticles of lonidamine in a rat BPH model created in rat prostates. After local injections of hybrid nanoparticles of lonidamine were administered to the rat prostates, hyperplasic structures of prostates were evaluated in terms of prostatic index values, immunohistochemical evaluations, and histopathological findings. Liver blood enzyme values were also determined to specify hepatic toxicity. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) reaction and histopathological methods to determine intravital degenerative destruction in liver. Through this study, lonidamine-loaded hybrid nanoparticles were found to reduce the hepatic toxicity and increase therapeutic efficiency of lonidamine. Therefore, lonidamine-entrapped hybrid nanoparticles may provide a promising, and very safe, drug delivery strategy in the treatment of BPH.

Inhibition of lysine acetyltransferases impairs tumor angiogenesis acting on both endothelial and tumor cells

Background

Understanding the signalling pathways involved in angiogenesis, and developing anti-angiogenic drugs are one of the major focuses on cancer research. Herein, we assessed the effect of CPTH6, a lysine acetyltransferase inhibitor and anti-tumoral compound, on angiogenesis-related properties of both endothelial and cancer cells.

Methods

The in vitro effect of CPTH6 on protein acetylation and anti-angiogenic properties on endothelial and lung cancer cells was evaluated via wound healing, trans-well invasion and migration, tube formation, immunoblotting and immunofluorescence. Matrigel plug assay, zebrafish embryo and mouse xenograft models were used to evaluate in vivo anti-angiogenic effect of CPTH6.

Results

CPTH6 impaired in vitro endothelial angiogenesis-related functions, and decreased the in vivo vascularization both in mice xenografts and zebrafish embryos. Mechanistically, CPTH6 reduced α-tubulin acetylation and induced accumulation of acetylated microtubules in the perinuclear region of endothelial cells. Interestingly, CPTH6 also affected the angiogenesis-related properties of lung cancer cells, and conditioned media derived from CPTH6-treated lung cancer cells impaired endothelial cells morphogenesis. CPTH6 also modulated the VEGF/VEGFR2 pathway, and reshaped cytoskeletal organization of lung cancer cells. Finally, anti-migratory effect of CPTH6, dependent on α-tubulin acetylation, was also demonstrated by genetic approaches in lung cancer cells.

Conclusion

Overall, this study indicates that α-tubulin acetylation could play a role in the anti-angiogenic effect of CPTH6 and, more in general, it adds information to the role of histone acetyltransferases in tumor angiogenesis, and proposes the inhibition of these enzymes as an antiangiogenic therapy of cancer.

Fasentin diminishes endothelial cell proliferation, differentiation and invasion in a glucose metabolism-independent manner

The synthetic compound fasentin has been described as a modulator of GLUT-1 and GLUT-4 transporters, thus inhibiting glucose uptake in some cancer cells. Endothelial glucose metabolism has been recently connected to angiogenesis and it is now an emerging topic in scientific research. Indeed, certain compounds with a known effect on glucose metabolism have also been shown to inhibit angiogenesis. In this work we tested the capability of fasentin to modulate angiogenesis in vitro and in vivo. We show that fasentin inhibited tube formation in endothelial cells by a mechanism that involves a negative effect on endothelial cell proliferation and invasion, without affecting other steps related to the angiogenic process. However, fasentin barely decreased glucose uptake in human dermal microvascular endothelial cells and the GLUT-1 inhibitor STF-31 failed to inhibit tube formation in these cells. Therefore, this modulatory capacity on endothelial cells function exerted by fasentin is most likely independent of a modulation of glucose metabolism. Taken together, our results show a novel biological activity of fasentin, which could be evaluated for its utility in cancer and other angiogenesis-dependent diseases.

Antitumor activity of a novel anti-vascular endothelial growth factor receptor-1 monoclonal antibody that does not interfere with ligand binding

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase transmembrane receptor that has also a soluble isoform containing most of the extracellular ligand binding domain (sVEGFR-1). VEGF-A binds to both VEGFR-2 and VEGFR-1, whereas placenta growth factor (PlGF) interacts exclusively with VEGFR-1. In this study we generated an anti-VEGFR-1 mAb (D16F7) by immunizing BALB/C mice with a peptide that we had previously reported to inhibit angiogenesis and endothelial cell migration induced by PlGF. D16F7 did not affect binding of VEGF-A or PlGF to VEGFR-1, thus allowing sVEGFR-1 to act as decoy receptor for these growth factors, but it hampered receptor homodimerization and activation. D16F7 inhibited both the chemotactic response of human endothelial, myelomonocytic and melanoma cells to VEGFR-1 ligands and vasculogenic mimicry by tumor cells. Moreover, D16F7 exerted in vivo antiangiogenic effects in a matrigel plug assay. Importantly, D16F7 inhibited tumor growth and was well tolerated by B6D2F1 mice injected with syngeneic B16F10 melanoma cells. The antitumor effect was associated with melanoma cell apoptosis, vascular abnormalities and decrease of both monocyte/macrophage infiltration and myeloid progenitor mobilization. For all the above, D16F7 may be exploited in the therapy of metastatic melanoma and other tumors or pathological conditions involving VEGFR-1 activation.

ROS homeostasis and metabolism: a critical liaison for cancer therapy

Evidence indicates that hypoxia and oxidative stress can control metabolic reprogramming of cancer cells and other cells in tumor microenvironments and that the reprogrammed metabolic pathways in cancer tissue can also alter the redox balance. Thus, important steps toward developing novel cancer therapy approaches would be to identify and modulate critical biochemical nodes that are deregulated in cancer metabolism and determine if the therapeutic efficiency can be influenced by changes in redox homeostasis in cancer tissues. In this review, we will explore the molecular mechanisms responsible for the metabolic reprogramming of tumor microenvironments, the functional modulation of which may disrupt the effects of or may be disrupted by redox homeostasis modulating cancer therapy.

Aberrant activation of the mTOR pathway and anti-tumour effect of everolimus on oesophageal squamous cell carcinoma

Background:

The mammalian target of rapamycin (mTOR) protein is important for cellular growth and homeostasis. The presence and prognostic significance of inappropriate mTOR activation have been reported for several cancers. Mammalian target of rapamycin inhibitors, such as everolimus (RAD001), are in development and show promise as anti-cancer drugs; however, the therapeutic effect of everolimus on oesophageal squamous cell carcinoma (OSCC) remains unknown.

Methods:

Phosphorylation of mTOR (p-mTOR) was evaluated in 167 resected OSCC tumours and 5 OSCC cell lines. The effects of everolimus on the OSCC cell lines TE4 and TE11 in vitro and alone or in combination with cisplatin on tumour growth in vivo were evaluated.

Results:

Mammalian target of rapamycin phosphorylation was detected in 116 tumours (69.5%) and all the 5 OSCC cell lines. Everolimus suppressed p-mTOR downstream pathways, inhibited proliferation and invasion, and induced apoptosis in both TE4 and TE11 cells. In a mouse xenograft model established with TE4 and TE11 cells, everolimus alone or in combination with cisplatin inhibited tumour growth.

Conclusion:

The mTOR pathway was aberrantly activated in most OSCC tumours. Everolimus had a therapeutic effect both as a single agent and in combination with cisplatin. Everolimus could be a useful anti-cancer drug for patients with OSCC.

Development of EGFR-targeted polymer blend nanocarriers for combination paclitaxel/lonidamine delivery to treat multi-drug resistance in human breast and ovarian tumor cells

Multi-drug resistant (MDR) cancer is a significant clinical obstacle and is often implicated in cases of recurrent, nonresponsive disease. Targeted nanoparticles were made by synthesizing a poly(D,L-lactide-co-glycolide)/poly(ethylene glycol)/epidermal growth factor receptor targeting peptide (PLGA/PEG/EGFR-peptide) construct for incorporation in poly(epsilon-caprolactone) (PCL) nanoparticles. MDR was induced in a panel of nine human breast and ovarian cancer cell lines using hypoxia. EGFR-targeted polymer blend nanoparticles were shown to actively target EGFR overexpressing cell lines, especially upon induction of hypoxia. The nanoparticles were capable of sustained drug release. Combination therapy with lonidamine and paclitaxel significantly improved the therapeutic index of both drugs. Treatment with a nanoparticle dose of 1 μM paclitaxel/10 μM lonidamine resulted in less than 10% cell viability for all hypoxic/MDR cell lines and less than 5% cell viability for all normoxic cell lines. Comparatively, treatment with 1 μM paclitaxel alone was the approximate IC₅₀ value of the MDR cells while treatment with lonidamine alone had very little effect. The PLGA/PEG/EGFR-peptide delivery system actively targets a MDR cell by exploiting the expression of EGFR. This system treats MDR by inhibiting the Warburg effect and promoting mitochondrial binding of pro-apoptotic Bcl-2 proteins (lonidamine), while hyperstabilizing microtubules (paclitaxel). This nanocarrier system actively targets a MDR associated phenotype (EGFR receptor overexpression), further enhancing the therapeutic index of both drugs and potentiating the use of lonidamine/paclitaxel combination therapy in the treatment of MDR cancer.

Functional activity of CXCL8 receptors, CXCR1 and CXCR2, on human malignant melanoma progression

We examined the autocrine/paracrine role of interleukin-8 (CXCL8) and the functional significance of CXCL8 receptors, CXCR1 and CXCR2, in human malignant melanoma proliferation, migration, invasion and angiogenesis. We found that a panel of seven cell lines, even though at different extent, secreted CXCL8 protein, and expressed CXCR1 and CXCR2 independently from the CXCL8 expression, but depending on the oxygen level. In fact, hypoxic exposure increases the expression of CXCR1 and CXCR2. The cell proliferation of both M20 and A375SM lines, expressing similar levels of both CXCR1 and CXCR2 but secreting low and high amounts of CXCL8, respectively, was significantly enhanced by CXCL8 exposure and reduced by CXCL8, CXCR1 and CXCR2 neutralising antibodies, indicating the autocrine/paracrine role of CXCL8 in melanoma cell proliferation. Moreover, an increased invasion and migration in response to CXCL8 was observed in several cell lines, and a further enhancement evidenced under hypoxic conditions. A CXCL8-dependent in vivo vessel formation, evaluated through a matrigel assay, was also demonstrated. Furthermore, when neutralising antibodies against CXCR1 or CXCR2 were used, only the involvement of CXCR2, but not CXCR1 was observed on cell migration and invasion, while both receptors played a role in angiogenesis. In summary, our data demonstrate that CXCL8 induces cell proliferation and angiogenesis through both receptors and that CXCR2 plays an important role in regulating the CXCL8-mediated invasive and migratory behaviour of human melanoma cells. Thus, blocking the CXCL8 signalling axis promises an improvement for the therapy of cancer and, in particular, of metastatic melanoma.

Telomere damage induced by the G-quadruplex ligand RHPS4 has an antitumor effect

Functional telomeres are required for the replicability of cancer cells. The G-rich strand of telomeric DNA can fold into a 4-stranded structure known as the G-quadruplex (G4), whose stabilization alters telomere function limiting cancer cell growth. Therefore, the G4 ligand RHPS4 may possess antitumor activity. Here, we show that RHPS4 triggers a rapid and potent DNA damage response at telomeres in human transformed fibroblasts and melanoma cells, characterized by the formation of several telomeric foci containing phosphorylated DNA damage response factors gamma-H2AX, RAD17, and 53BP1. This was dependent on DNA repair enzyme ATR, correlated with delocalization of the protective telomeric DNA-binding protein POT1, and was antagonized by overexpression of POT1 or TRF2. In mice, RHPS4 exerted its antitumor effect on xenografts of human tumor cells of different histotype by telomere injury and tumor cell apoptosis. Tumor inhibition was accompanied by a strong DNA damage response, and tumors overexpressing POT1 or TRF2 were resistant to RHPS4 treatment. These data provide evidence that RHPS4 is a telomere damage inducer and that telomere disruption selectively triggered in malignant cells results in a high therapeutic index in mice. They also define a functional link between telomere damage and antitumor activity and reveal the key role of telomere-protective factors TRF2 and POT1 in response to this anti-telomere strategy.

Modulation of bcl-xL in tumor cells regulates angiogenesis through CXCL8 expression

In this paper, we investigated whether bcl-xL can be involved in the modulation of the angiogenic phenotype of human tumor cells. Using the ADF human glioblastoma and the M14 melanoma lines, and their derivative bcl-xL-overexpressing clones, we showed that the conditioned medium of bcl-xL transfectants increased in vitro endothelial cell functions, such as proliferation and morphogenesis, and in vivo vessel formation in Matrigel plugs, compared with the conditioned medium of control cells. Moreover, the overexpression of bcl-xL induced an increased expression of the proangiogenic interleukin-8 (CXCL8), both at the protein and mRNA levels, and an enhanced CXCL8 promoter activity. The role of CXCL8 on bcl-xL-induced angiogenesis was validated using CXCL8-neutralizing antibodies, whereas down-regulation of bcl-xL through antisense oligonucleotide or RNA interference strategies confirmed the involvement of bcl-xL on CXCL8 expression. Transient overexpression of bcl-xL led to extend this observation to other tumor cell lines with different origin, such as colon and prostate carcinoma. In conclusion, our results showed that CXCL8 modulation by bcl-xL regulates tumor angiogenesis, and they point to elucidate an additional function of bcl-xL protein.

Expression of cyclooxygenase-2, vascular endothelial growth factor and matrix metalloproteinase-2 in patients with primary laryngeal carcinoma: a tissue microarray study

OBJECTIVE

To determine the correlation between expression of cyclooxygenase-2, vascular endothelial growth factor and matrix metalloproteinase-2, in patients with laryngeal carcinoma.

DESIGN

The study included 85 primary laryngeal squamous cell carcinoma cases. Expression was assessed using Envision immunohistochemical stains for cyclooxygenase-2, vascular endothelial growth factor and matrix metalloproteinase-2.

SUBJECTS

A tissue microarray containing samples from the 85 primary laryngeal squamous cell carcinoma cases was assembled. Immunohistochemical testing for cyclooxygenase-2, vascular endothelial growth factor and matrix metalloproteinase-2 was performed. Using Pearson correlation, expression of these proteins was compared with the following clinicopathological variables: age, sex, clinical tumour-node-metastasis staging, and prognosis. Three-year survival curves, factored by cyclooxygenase-2, vascular endothelial growth factor and matrix metalloproteinase-2 expression, were generated for overall survival, by Kaplan-Meier analysis.

RESULTS

The expression of cyclooxygenase-2 significantly differed between patients with different pathology, tumour-node-metastasis stage and prognosis. A marked difference in vascular endothelial growth factor expression was seen between two histological grade groups. Expression of matrix metalloproteinase-2 protein statistically significantly differed between patients with different tumour-node-metastasis stages, lymph node metastases and three-year survival rates. The expression of cyclooxygenase-2 in laryngeal carcinoma tissue was found to be associated with the expression of matrix metalloproteinase-2.

CONCLUSION

Cyclooxygenase-2 and matrix metalloproteinase-2 may act as clinical prognostic indicators of tumour growth and differentiation in laryngeal carcinoma.

Antiangiogenic potential of the Mammalian target of rapamycin inhibitor temsirolimus

Mammalian target of rapamycin (mTOR) is increasingly recognized as a master regulator of fundamental cellular functions, whose deregulation may underlie neoplastic transformation and progression. Hence, mTOR has recently emerged as a promising target for therapeutic anticancer interventions in several human tumors, including breast cancer. Here, we investigated the antiangiogenic potential of temsirolimus (also known as CCI-779), a novel mTOR inhibitor currently in clinical development for the treatment of breast cancer and other solid tumors. Consistent with previous reports, sensitivity to temsirolimus-mediated growth inhibition varied widely among different breast cancer cell lines and was primarily due to inhibition of proliferation with little, if any, effect on apoptosis induction. In the HER-2 gene-amplified breast cancer cell line BT474, temsirolimus inhibited vascular endothelial growth factor (VEGF) production in vitro under both normoxic and hypoxic conditions through inhibition of hypoxia-stimulated hypoxia-inducible factor (HIF)-1alpha expression and transcriptional activation. Interestingly, these effects were also observed in the MDA-MB-231 cell line, independent of its inherent sensitivity to the growth-inhibitory effects of temsirolimus. A central role for mTOR (and the critical regulator of cap-dependent protein translation, eIF4E) in the regulation of VEGF production by BT474 cells was further confirmed using a small interfering RNA approach to silence mTOR and eIF4E protein expression. In addition to its effect on HIF-1alpha-mediated VEGF production, temsirolimus also directly inhibited serum- and/or VEGF-driven endothelial cell proliferation and morphogenesis in vitro and vessel formation in a Matrigel assay in vivo. Overall, these results suggest that antiangiogenic effects may substantially contribute to the antitumor activity observed with temsirolimus in breast cancer.

Trastuzumab down-regulates Bcl-2 expression and potentiates apoptosis induction by Bcl-2/Bcl-XL bispecific antisense oligonucleotides in HER-2 gene--amplified breast cancer cells

PURPOSE

To investigate the possible existence of an antiapoptotic cross-talk between HER-2 and antiapoptotic Bcl-2 family members.

EXPERIMENTAL DESIGN

Bcl-2 and Bcl-XL expression and apoptosis induction were analyzed in HER-2 gene-amplified (BT474) and nonamplified (ZR 75-1) breast cancer cell lines exposed to trastuzumab, alone or in combination with either Bcl-2/Bcl-XL bispecific antisense oligonucleotides (AS-4625) or the small-molecule Bcl-2 antagonist HA14-1.

RESULTS

In addition to HER-2 and epidermal growth factor receptor, trastuzumab down-regulated Bcl-2, but not Bcl-XL, protein, and mRNA expression in BT474 cells. Interestingly, trastuzumab-induced down-regulation of HER-2 and Bcl-2 was also observed in three of five and two of three breast cancer patients undergoing trastuzumab treatment, respectively. Despite Bcl-2 down-regulation, however, trastuzumab only marginally increased the rate of apoptosis (7.3 +/- 3.5%). We therefore investigated whether a combination of AS-4625 and trastuzumab might increase proapoptotic efficiency. AS-4625 treatment of BT474 cells decreased both Bcl-2 and Bcl-XL expression, resulting in a 21 +/- 7% net apoptosis induction; the combination of AS-4625 followed by trastuzumab resulted in a significantly stronger induction of apoptosis (37 +/- 6%, P <0.01) that was not observed with the reverse treatment sequence (trastuzumab followed by AS-4625). Similar results were obtained with the Bcl-2 antagonist HA14-1; indeed, exposure of BT474 cells to HA14-1 followed by trastuzumab resulted in a striking proapoptotic synergism (combination index=0.58 +/- 0.18), as assessed by isobologram analysis.

CONCLUSIONS

Altogether our findings suggest that combined targeting of HER-2 and Bcl-2 may represent a novel, rational approach to more effective breast cancer therapy.