Efficacy Of Chemotherapeutic Agents Research Articles

Biomarkers in Breast Cancer and the Implications of Their Discordance

The analysis of biomarkers in breast cancer has made a large impact in treatment decisions and determining prognosis. Information gained from the phenotypic and molecular profile helps both in prognostic stratification as well as treatment selection. With the advent of newer more efficacious chemotherapeutic and biological agents in the management of metastatic breast cancer, most women with this disease are exposed to multiple lines of therapy. Discordance in the receptor status between the primary and metastatic sites is frequently encountered and may play an important role in deciding subsequent therapy. In this review, we look at the role of current biomarkers in the management of breast cancer, which are promising and the therapeutic and prognostic implications of their discordance during the natural course of disease progression.

Anti-CD30 antibody conjugated liposomal doxorubicin with significantly improved therapeutic efficacy against anaplastic large cell lymphoma

The use of nano-carriers has been shown to improve the delivery and efficacy of chemotherapeutic agents in cancer patients. Recent studies suggest that decoration of the surface of nano-carriers with various targeting moieties may further improve the overall therapeutic efficacy. In this study, we compared the therapeutic efficacy of Doxil® (commercial doxorubicin-loaded liposomes) and that of Doxil® conjugated with anti-CD30 antibodies (CD30-targeted Doxil®) in treating anaplastic large cell lymphoma (ALCL), a type of T-cell lymphoma characterized by a high CD30 expression. Compared to Doxil®, the CD30-targeted Doxil® showed a significantly higher binding affinity to ALCL cells (5.3% versus 27%, p = 0.005) and a lower inhibitory concentration at 50% (IC50) in-vitro (32.6 μg/mL versus 12.6 μg/mL, p = 0.006). In a SCID mouse xenograft model, CD30-targeted Doxil® inhibited tumor growth more significantly than the unconjugated formulation; specifically, tumors in mice treated with CD30-targeted Doxil® were significantly smaller than those in mice treated with Doxil® (average, 117 mm3 versus 270 mm3, p = 0.001) at 18 days after the tumors were inoculated. Our findings have provided the proof-of-principle of using CD30-targeted nano-carriers to treat cancers that are characterized by a high level of CD30 expression, such as ALCL.

Abstract 4959: Targeting pancreatic stellate cells (PSC) to treat pancreatic cancer.

Abstract Pancreatic cancer (PC) is characterized by a prominent stromal reaction. Recently, the contribution of the stromal elements to the initiation and progression of the disease has come to be appreciated. In this context, targeting this tumor microenvironment represents a potential strategy to improve the delivery and efficacy of chemotherapeutic agents leading a better prognosis for the patients. Pancreatic stellate cells (PSC) have been recognized as the principal cells responsible for the production of fibrosis in pancreatic cancer. In the current study, we observed that PSC possess α-naphthyl acetate esterase (ANAE) activity, which is a specific marker enzyme for monocytes and macrophages, these cells can be differentiated/activated in a similar fashion as a monocytes/macrophages, suggesting that PSC behave in a similar fashion as macrophages, and hence can be treated as such. Based on these data we targeted PSC in vitro and in vivo by using bisphosphonates (BPs) that are macrophages inhibitors. BPs inhibited proliferation and inactivated PSC in vitro through inhibition of protein prenylation, and increased cell apoptosis and cell cycle arrest in G1. Furthermore, BPs inactivated PSC, inhibited tumor growth (p<0.0005), tumor weight (p<0.001) and number of nodules (p<0.001) in an orthotopic animal model of pancreas. These antitumor effects were enhanced when BPs were combined with a taxane. These data suggest that BPs could disrupt the pancreatic cancer, which could offer a better prognosis to PC patients. Citation Format: Vianey Gonzalez-Villasana, Cristian Rodriguez-Aguayo, Thiru Arumugam, Zobeida Cruz-Monserrate, Defeng Deng, Enrique Fuentes-Mattei, Rosa F. Hwang, Huamin Wang, Guillermo N. Armaiz Pena, Burcu Aslan, Yolanda Gutierrez-Puente, Anil K. Sood, Craig Logsdon, Gabriel Lopez-Berestein. Targeting pancreatic stellate cells (PSC) to treat pancreatic cancer. [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 4959. doi:10.1158/1538-7445.AM2013-4959

Pathology vs medical oncology: the crucial exchange of accurate information

Over the past two decades we have seen some truly exciting advances made in the biological understanding, diagnosis and management of breast cancer. We now recognise that breast cancer is a heterogeneous disease made of up of several subtypes. The introduction of an anthracycline polychemotherapy adjuvant regimen has reduced the 10-year breast cancer mortality by approximately one-third and the introduction of the monoclonal antibody trastuzumab for the treatment of HER2-positive breast cancer has in the adjuvant setting been associated with an unprecedented relative improvement in disease-free survival by almost 50%. Research is now focused on further improving prognostic outcome by exploring novel biomarkers that will better select patients requiring chemotherapy, identification and development of agents to overcome primary and secondary resistance of tumours to existing therapeutic agents as well as introducing new more efficacious chemotherapeutic and biological agents into adjuvant treatment protocols.

Role of the Immune Tolerance-Inducing Molecule Indoleamine 2,3-Dioxygenase in Gynecologic Cancers

Immune escape and acquisition of tolerance by tumor cells are essential to cancer growth and progression. Therefore, considerable attention has been paid to overcoming the immune resistance of tumors as a novel strategy for cancer therapy. This review focuses on the tryptophan-catabolizing and immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO), and its functional role in gynecologic cancers, such as endometrial cancer, ovarian cancer, cervical cancer, and vulvar cancer. IDO induces tolerance to the host immune surveillance through suppressing the proliferation of effector T-cells or natural killer cells and their killer functions within the tumor microenvironment. In gynecologic cancers, IDO is highly expressed in more than half of cases, and tumoral IDO expression is correlated with advanced surgical stage and impaired patient survival. In preclinical studies in mice, an IDO inhibitor 1-methyltryptophan suppresses tumor growth and peritoneal dissemination, and increases the efficacy of chemotherapeutic agents. In summary, IDO is a novel prognostic indicator for endometrial, ovarian, cervical, and vulvar cancers. IDO inhibition may be a promising strategy to restore host anti-tumor immunity and to enhance the anti-tumor potential of current chemotherapy, radiotherapy, and immunotherapy for gynecologic cancers.

715P - Timing and Patterns of Disease Progression Following Concurrent Radiochemotherapy in Patients with Unresectable Locally-Advanced Pancreas Cancer

ABSTRACT Background Timing and patterns of disease progression in patients with unresectable locally-advanced pancreas carcinoma (LAPC) treated with definitive concurrent radiochemotherapy (C-RCT) was analyzed. Materials and method Fifty-two patients with histologic proof of LAPC underwent 50.4 Gy (1.8 Gy per fraction) of C-RCT with 5-FU followed by maintenance gemcitabine. Disease was considered to be unresectable if contrast-enhanced CT or staging laparoscopy/laparotomy revealed a low likelihood of complete resection and/or any of the following: involvement of superior mesenteric artery/cealiac trunk, encasement of 180 degrees or more of the circumference of superior mesenteric/portal vein, and/or evidence of narrowing of or thrombus within the superior mesenteric/portal vein. Elective nodal irradiation was not adopted. Primary aim was to assess timing and patterns of disease progression. Results Treatment was well tolerated and all patients were able to receive intended C-RCT regimen. At median 17.4 months of follow-up 38 (73.1%) were dead. Median, 1- and 2-year overall- and progression-free survival estimates were 16.1 months, 61.2% and 22.6%, and 7.4 months, 27% and 12.3% respectively. Analysis for timing of disease progression revealed that 7 (13.5%), 15 (28.8%), 20 (38.5%), and 22 (42.3%) patients experienced disease progression at 3, 4, 5, and 6 months, respectively, since initiation of R-RCT. Interestingly, although there were no isolated local or regional failures during this early follow-up period, all failures were presented as distant metastases with/without local/regional disease progression. Conclusion Results of this study demonstrated that, despite aggressive staging and treatment strategies, early distant disease progression are common source of treatment failures in unresectable LAPC. Present findings impact the urgent need for more efficacious chemotherapeutic agents for control of distant metastatatic tumor deposits and better treatment strategies, such as induction chemotherapy followed by C-RCT, to eliminate early treatment failures and unnecessary and futile C-RCT in metastatic disease state. Disclosure All authors have declared no conflicts of interest.

The anti-Fn14 antibody BIIB036 inhibits tumor growth in xenografts and patient derived primary tumor models and enhances efficacy of chemotherapeutic agents in multiple xenograft models

Agonistic antibodies targeting Fn14, the receptor for TWEAK, have demonstrated anti-tumor activity in xenograft models. Herein, we further explore the therapeutic potential of the humanized anti-Fn14 agonistic antibody, BIIB036, as a single agent and in combination with standard of care cancer therapeutics. Pharmacokinetic studies of BIIB036 in tumor-bearing mice revealed a half-life of approximately three days suggesting twice a week dosing would be necessary to maintain efficacy. However, in multiple xenograft models, BIIB036 treatment resulted in extended tumor growth inhibition up to 40–50 d following cessation of dosing, suggesting that frequent administration of BIIB036 may not be necessary to maintain prolonged anti-tumor activity. Subsequent xenograft studies revealed that maximal efficacy was achieved with BIIB036 dosing once every two weeks, by either intraperitoneal or subcutaneous administration. Xenograft tumors that were initially treated with BIBI036 and then re-grew up to 1000 mm3 following cessation of the first cycle of treatment remained sensitive to a second cycle of treatment. BIIB036 was also evaluated in patient derived primary colon tumor models, where efficacy compared favorably with a standard of care agent. Lastly, BIIB036 enhanced the efficacy of several standard of care chemotherapeutics, including paclitaxel in MDA-MBA-231 breast tumor xenografts, paclitaxel or carboplatin in HOP62 non-small cell lung xenografts, and 5-FU in NCI-N87 gastric xenografts, with no overlapping toxicities. These studies thus establish BIIB036 as a promising therapeutic agent with durable anti-tumor activity in human xenografts as well as patient derived primary tumor models, and enhanced activity and tolerability in combination with standard of care chemotherapeutics. Taken together, the data presented herein suggest that BIIB036 warrants evaluation in the clinic.

Abstract 4227: Sensitizing resistant ovarian cancer to chemotherapy through inhibition of small GTPases

Abstract Platinum- or paclitaxel-resistance is a major problem in women with advanced ovarian cancer (OVCA) and that confers a poor prognosis for patients. Consequently there is a great need to identify new drugs and drug targets for the management of residual and recurrent metastatic OVCA. About 90% of OVCA starts on the ovarian surface epithelium, but individual cells or multicellular aggregates (MCAs) shed into the peritoneal cavity and contribute to OVCA's metastasis into adjacent organs. These MCAs are resistant to apoptosis and to radio- and chemo-therapy. In OVCA, resistance to chemotherapy and apoptosis has been linked to the small GTPases, Rac1 and Cdc42, and their downstream effectors. Identifying compounds that disperse MCAs through disrupting adhesions would sensitize this resistant subpopulation to chemotherapy. We hypothesize that inhibition of one or both of these GTPases disrupts MCAs and sensitizes drug-resistant OVCA cells to respond to chemotherapeutic agents. We assessed if chemical inhibition of Rac1 or Cdc42 would sensitize drug-resistant OVCA monolayers and in vitro MCAs to cisplatin's cytotoxicity. The OVCA cell lines evaluated were OVCA 429 and SKOV-3ip. The inhibitors we used included: (1) NSC 23766, a Rac1-specific inhibitor, (2) ML141, a Cdc42-specific inhibitor, (3) Toxin B, an inhibitor of Rac, Cdc42 and Rho, and (4) R-naproxen, an inhibitor of Rac1 and Cdc42 (based on our data). We found that Rac1 and Cdc42 inhibitors disperse MCAs in a liquid overlay assay. Furthermore, these inhibitors sensitized OVCA cells to cisplatin's cytotoxic effect. Finding drugs that increase efficacy of chemotherapeutic agents against resistant OVCA cell populations is of particular importance. Thus far, GTPases have not been extensively examined as therapeutic targets, but they offer new opportunities for OVCA therapy. Our findings indicate that Rac1 and Cdc42 inhibitors disperse MCAs and improve their response to chemotherapeutic agents. This could increase the effectiveness of intraperitoneal chemotherapy and improve patient outcomes and survival. Since one of these inhibitors is R-Naproxen (an FDA approved off-patent drug), it has potential for rapid clinical application. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4227. doi:1538-7445.AM2012-4227

Mechanisms of Cisplatin-Induced Apoptosis and of Cisplatin Sensitivity: Potential of BIN1 to Act as a Potent Predictor of Cisplatin Sensitivity in Gastric Cancer Treatment

Cisplatin is the most important and efficacious chemotherapeutic agent for the treatment of advanced gastric cancer. Cisplatin forms inter- and intrastrand crosslinked DNA adducts and its cytotoxicity is mediated by propagation of DNA damage recognition signals to downstream pathways involving ATR, p53, p73, and mitogen-activated protein kinases, ultimately resulting in apoptosis. Cisplatin resistance arises through a multifactorial mechanism involving reduced drug uptake, increased drug inactivation, increased DNA damage repair, and inhibition of transmission of DNA damage recognition signals to the apoptotic pathway. In addition, a new mechanism has recently been revealed, in which the oncoprotein c-Myc suppresses bridging integrator 1 (BIN1), thereby releasing poly(ADP-ribose)polymerase 1, which results in increased DNA repair activity and allows cancer cells to acquire cisplatin resistance. The present paper focuses on the molecular mechanisms of cisplatin-induced apoptosis and of cisplatin resistance, in particular on the involvement of BIN1 in the maintenance of cisplatin sensitivity.

Dendrimer phthalocyanine-encapsulated polymeric micelle-mediated photochemical internalization extends the efficacy of photodynamic therapy and overcomes drug-resistance in vivo

Clinically, the efficacy of chemotherapeutic agents can be dramatically reduced in cancer cells with multiple drug resistance (MDR). In doxorubicin-resistant breast cancer cells, drugs accumulate only within discrete cytosolic organelles that abrogate their therapeutic effects in vitro and in vivo. Photochemical internalization (PCI), a specific branch of photodynamic therapy (PDT), is a novel strategy utilized for the site-specific triggered drug/gene release. The objective of this study was to evaluate the nanoparticle-based PDT/PCI effects on the reversal of drug resistance. Dendrimer phthalocyanine-encapsulated polymeric micelle (DPc/m)-mediated PCI, combined with doxorubicin, was studied in drug-resistant MCF-7 cells and a xenograft model. Our results show that the internalized DPc/m showed unique PCI properties inside the cells and thereby facilitating doxorubicin release from the endo-lysosomes to nuclei after photoirradiation. Moreover, ‘light before’ PCI showed the highest antitumor efficacy and the depth of the proliferating cell nuclear antigen-negative area in tumor sections after DPc/m-mediated PDT was obviously increased by combination therapy with doxorubicin; this indicates the limitation of depth of light penetration in PDT, which may be improved by PCI. We conclude that nanotechnology-based PCI possesses several clinical benefits, such as overcoming drug resistance and treating deeper lesions that are intractable by PDT alone.

Increased Vascular Delivery and Efficacy of Chemotherapy after Inhibition of Platelet-Derived Growth Factor-B

Inhibition of platelet-derived growth factor-B (PDGF-B) has multiple effects on tumors, including loss of pericytes, regression of some vessels, normalization of other vessels, and reduction of interstitial pressure. PDGF-B inhibition also increases the efficacy of cancer therapeutics, but the role on tumor vessel efficiency and drug delivery is unclear. We sought to determine whether inhibition of PDGF-B signaling can increase delivery and efficacy of cyclophosphamide in Lewis lung carcinomas or RIP-Tag2 tumors. PDGF-B blockade in Lewis lung carcinoma tumors by the DNA aptamer AX102 for 14 days increased the number of perfused tumor vessels marked by lectin in the bloodstream by 50%. AX102 also increased the width of sleeves of viable tumor cells around blood vessels by 66%, increased tumor cell proliferation by 90%, and increased intratumoral delivery of Hoechst 33342 by 78%. A low dose of cyclophosphamide (20 mg/kg) reduced tumor cell proliferation by 31% when combined with AX102 but not when given alone. Synergy of cyclophosphamide and AX102 on tumor cell proliferation also was found in RIP-Tag2 tumors. Similarly, the PDGF receptor signaling inhibitor imatinib increased delivery of cyclophosphamide and reduced tumor burden in RIP-Tag2 mice, without evidence of tumor cell sensitization to chemotherapy. Together, these findings indicate that inhibition of PDGF-B signaling promotes the delivery and efficacy of chemotherapeutic agents by increasing the efficiency of tumor blood vessels.

Abstract 715: TGF-beta blockade improves the distribution and efficacy of chemotherapeutic agents in breast carcinoma

Abstract Although the role of TGF-β has been studied extensively, its impact upon drug delivery within tumors remains poorly understood. In this study, we blocked the TGF-β pathway in mouse models of breast cancer and studied the effect on delivery and efficacy of chemotherapeutics. We used both genetic (overexpression of sTβRII, a soluble TGF-β type II receptor) and pharmaceutical (1D11, a TGF-β antibody) approaches to block the TGF-β signaling in two orthotopic breast cancer models (human MDA-MB-231 cells and murine 4T1 cells). TGF-β blockade significantly decreased the growth and metastasis of orthotopic human breast carcinoma xenografts. In addition, TGF-β blockade increased the recruitment and incorporation of myofibroblasts into tumor blood vessels and restored vascular perfusion. Moreover, TGF-β blockade normalized the tumor extracellular matrix (ECM) by decreasing collagen I content. As a result of this vessel and ECM normalization, TGF-β blockade improved the transvascular and interstitial transport of both small and large molecular weight chemotherapeutic agents, and consequently enhanced their efficacy. In conclusion, our study shows that TGF-β blockade might represent a new approach to improve delivery of both low molecular weight conventional drugs as well as nanomedicines in order to maximize therapeutic outcomes. 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 715. doi:10.1158/1538-7445.AM2011-715

Abstract 2555: Drug repositioning: Propanolol potentiates the anticancer efficacy of chemotherapeutic agents through modulation of angiogenesis

Abstract Background: Recently, the beta-blocker propranolol was found to be of clinical benefit in the treatment of severe hemangioma of infancy. Although its precise mechanisms of action have not been fully elucidated, it could involve vasoconstriction, inhibition of angiogenic signalling and direct induction of apoptosis in endothelial cells. Here, we evaluate whether propranolol could improve the antitumor efficacy of standard chemotherapeutic agents. Methods: The impact of adding concomitantly propranolol to 5-FU was first investigated on a representative panel of human colorectal, breast and medulloblastoma cell lines (SW620, HT29, BT474, MDA231, HTB186). Their effects on angiogenesis were further investigated in 2 different endothelial cell lines (HMEC-1 and BMH29L), by Matrigel assay using time-lapse videomicroscopy. The combination treatment was then evaluated in 2 different xenograft mouse models of human breast cancer. Results: Propranolol showed little cytotoxic activity at clinically relevant concentrations in vitro. Results from combination studies of 5-FU and propranolol were cell line-dependent and ranged from no significant effect (HTB186, SW620), to additivity (HT29, BT474), and synergism (MDA-231). Increase in early and late apoptosis, with accumulation in the sub-G0/G1 phase, was observed in the most sensitive models exposed to the combination of 5-FU and propranolol. In endothelial cells, combination index calculations revealed a synergistic effect on angiogenesis (CI = 0.54 ± 0.09). For instance, 5-FU and propranolol alone (50 µM) inhibited the differentiation of HMEC-1 cells into vascular structures by 10 and 27%, respectively while the equimolar combination of drugs resulted in a 52% inhibition (p<0.001). In vivo, all treatments were well tolerated. In the MDA-231 orthotopic model, 5-FU (30 mg/kg 3QW × 5wks) alone achieved only mild reduction in tumor size (−38% at Day-30; n.s.) as compared with control animals. Combining 5-FU with low (0.15 mg/kg) and high (7 mg/kg) doses of propranolol led to a further 49 and 70% reduction in tumor growth, respectively (Day-30; p<0.05). Accordingly, the combination led to a marked increase in animal survival. Mean survival at Day-50 increased from 0% (control) and 44% (5-FU) to 77% (combination). Finally, additional in vitro angiogenesis experiments revealed a powerful synergism between propranolol and paclitaxel. Further investigations are currently underway to validate the potential efficacy of the propranolol/paclitaxel combination in vitro and in vivo. Conclusions & perspectives: This study provides strong evidence that propranolol can improve the antitumor efficacy of major cytotoxic drugs in vitro and in vivo. Propranolol mediates these effects, at least in part, through anti-angiogenic mechanisms. Additional studies are currently ongoing to refine the mechanisms of action of propranolol. 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 2555. doi:10.1158/1538-7445.AM2011-2555

Abstract 3626: Targeting of essential gene products in breast cancer with cell penetrating neutralizing antibodies

Abstract We present a novel nuclear, targeted therapeutic strategy that disrupts intracellular essential gene products selectively in tumors. Therapeutic antibodies against external cell surface receptors are effective. However, the limited permeability of antibodies through cellular and nuclear membranes restricts their use as therapeutics for targeting intracellular gene products of cancer cells. Many of the oldest and most efficacious cancer chemotherapeutic agents target cellular elements essential to the growth and proliferation of all cells (e.g. DNA with alkylating agents or dihydrofolate reductase with methotrexate) accentuating the utility of targeting essential gene products. However, the toxicity of traditional broad-based drugs to normal cells is high, limiting its utility. Thus, we seek to inactivate essential gene products by selectively delivering targeted biologic therapeutics, i.e. neutralizing monoclonal antibodies, against specific intracellular essential gene products thereby killing cancer cells. To selectively target tumors, we are employing tumor-associated protease “activatable” cell penetrating peptide (CPP) motif described by Tsein and co-workers. To demonstrate our novel approach, we are initially focusing on the intracellular delivery of RPA70 which is an essential gene product that functions in DNA replication and is found to be an attractive therapeutic target in breast and prostate cancers. Thus far, we synthesized a cell penetrating peptide (CPP) and a tumor-associated “activatable” CPP that can be conjugated to IgGs. We screened various bioconjugation techniques and found that thiolation of IgG with thiolane followed by incubation with CPP-maleimide was the most efficient with good CPP-to-antibody ratio. With these antibody bioconjugates, we are able to show that anti-RPA70 and control antibodies were taken up to the cytoplasm as well as into the nucleus of cells. Monitoring of cell growth and proliferation of cancer cell lines in the presence of CPP-anti-RPA70 are underway. Progress in these studies will also be presented. 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 3626. doi:10.1158/1538-7445.AM2011-3626

Abstract LB-202: Therapeutic efficacy of coencapsulated cisplatin and arsenic trioxide nanobins in murine models of breast cancer

Abstract We have developed a novel strategy to encapsulate a combination of cisplatin and arsenic trioxide as a precipitate inside 100 nm liposomal nanobins, NB(Pt, As). Cisplatin is a widely used chemotherapeutic but has significant dose-limiting toxicity. Arsenic trioxide (ATO) is a potent FDA-approved therapy for acute promyelocytic leukemia; however, ATO has not been effective in clinical trials of solid tumors. Encapsulation in nanoliposomes can improve the anti-cancer efficacy of chemotherapeutic agents by extending serum half-life, increasing tumor drug delivery and attenuating toxicity. We have tested the therapeutic efficacy of NB(Pt, As) in orthotopic xenograft models of triple negative breast cancer using MDA-MB-231 and MDA-MB-435/LvBr1 cancer cell lines. Treatment with either NB(Pt, As) or cisplatin for three weeks inhibited growth of MDA-MB-231 mammary tumors in vivo. However, the NB(Pt, As) did not cause weight loss in treated animals and did not result in abnormal serum chemistries. NB(Pt, As) was also evaluated for its ability to inhibit lung metastases. Mice inoculated intraductally with highly metastatic MDA-MB-435/LvBr1 cancer cells develop mammary tumors that metastasize and form macroscopic lesions in the lung. Treatment with NB(Pt, As) was initiated when primary tumors reached∼250 mm3. Both NB(Pt, As) and cisplatin inhibited primary tumor growth in this model, whereas only NB(Pt, As) treatment significantly reduced lung metastatic burden. Our results suggest that nanobin encapsulated cisplatin and ATO is a promising nanoscale therapeutic agent for metastatic breast cancer. 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 LB-202. doi:10.1158/1538-7445.AM2011-LB-202

Abstract 1710: Expression of erbB3 upregulates Survivin via transcription-independent mechanism in erbB2-overexpressing breast cancer cells to confer Paclitaxel resistance

Abstract The erbB2 receptor is often activated via dimerization with another erbB receptor, such as EGFR or erbB3. Studies show that co-expression of erbB3 and erbB2 is frequently observed in breast cancer; and erbB2 requires erbB3 to stimulate breast cancer cell proliferation. Increased resistance to therapeutic agents such as paclitaxel is one of the mechanisms by which erbB2 contributes to breast tumorigenesis. While several molecular mechanisms contributing to paclitaxel resistance have been proposed, a series studies demonstrate that overexpression of erbB2 inhibits paclitaxel-induced apoptosis in breast cancer cells. However, the role of erbB3 in paclitaxel resistance remains unclear. Our current studies focus on determining the role(s) of erbB3 in erbB2-mediated paclitaxel resistance in breast cancer cells. Overexpression of exogenous erbB3 via either stable or transient transfection in erbB2-overexpressing, but not EGFR-expressing, breast cancer cells significantly decreases paclitaxel-induced growth inhibition and apoptosis. Consistently, knockdown of erbB3 expression with a specific shRNA in breast cancer cells with coexpression of both erbB2 and erbB3 enhances paclitaxel-induced apoptosis evidenced by increased DNA fragmentation, PARP cleavage, and activation of caspase-3, and -8. Furthermore, while forced overexpression of erbB3 increases, specific knockdown of erbB3 decreases the protein but not mRNA expression levels of Survivin only in the erbB2-overexpressing breast cancer cells. Targeting Survivin with specific shRNA overcomes paclitaxel resistance without effect on the expression levels of either erbB2 or erbB3. Mechanistic studies indicate that the specific PI-3K, Akt, and mTOR inhibitors, but not the MEK inhibitor, not only abrogate erbB3-mediated upregulation of Survivin, but also reinforce the erbB2/erbB3-coexpressing breast cancer cells to paclitaxel-induced growth inhibition. Our studies demonstrate that heterodimerization of erbB2/erbB3 results in paclitaxel resistance in breast cancer cells via PI-3K/Akt/mTOR signaling pathway. Elevated expression of erbB3 upregulates Survivin through transcription-independent mechanism in erbB2-overexpressing cancer cells, suggesting that novel strategies targeting erbB3 or Survivin protein translation may enhance the efficacy of chemotherapeutic agents against breast cancer with erbB2-overexpressing tumors. 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 1710. doi:10.1158/1538-7445.AM2011-1710

Abstract LB-196: A folate receptor-targeted nanoparticle minimizes multidrug resistance in human cancer xenograft model

Abstract Resistance to chemotherapy is a major obstacle in cancer therapy. Intrinsic or acquired drug resistance occurs frequently in most cancers. In this report, we developed a novel nanoparticle formulation with the intent of significantly increasing the bioavailability and enhancing the efficacy of chemotherapeutic agent, paclitaxel in the experimental model of resistant human squamous cell carcinama. The targeted nanoparticle (HFT-T) was loaded with paclitaxel in its hydrophobic core, which is composed of Heparin-Folate-Paclitaxel (HFT) conjugates (Wang X., et al. ACS Nano 2009, 3, 3165–3174). In vitro cytotoxicity of nanoparticle HFT-T was assessed on a resistant human squamous cancer cell line KB-8–5 (ten time resistant to paclitaxel compare to the sensitive cell line KB-3–1). The targeted nanoparticle HFT-T was more effective in inhibiting cell growth, when compared with non-targeted nanoparticle (HT-T) or free paclitaxel in multidrug resistance cells. In vitro cellular uptake, retention, and efflux of HFT-T nanoparticles studies suggested that the HFT-T formulation may counteract the transporter-mediated drug resistance in KB-8–5 cells, thereby increasing intracellular concentrations of paclitaxel and enhancing its cytotoxicity. Compared to free paclitaxel, HFT-T was found to be capable of effectively delivering and maintaining markedly higher concentrations (by 2∼3-fold) of paclitaxel in KB-8–5 cells when added to the cultures at various times. To test the in vivo efficacy of HFT-T particles, nude mice bearing subcutaneous human KB-8–5 tumors were randomly divided into four groups (n=8 per group), and treated with HFT-T, free paclitaxel, HT-T or PBS (control), respectively. The drugs (at a dose of 40 mg/kg paclitaxel or equivalent) were administrated intravenously via tail vein once a week for 3 weeks (3 injections in total). At the end of the experiment, the tumor volume in the HFT-T-treated group were significantly reduced compared with all other treatment groups including the control (p=0.0075), free paclitaxel (p=0.0155), and HT-T (p=0.0381) treated groups. In contrast, tumor volumes in paclitaxel (p=0.2287) or HT-T-treated (P=0.1423) groups were not significantly different from the control group. The results indicated that the therapeutic efficacy of targeting HFT-T nanoparticle is significantly superior to free paclitaxel and non-targeted nanoparticle in drug-resistant xenograft models. In conclusion, this study provides a novel strategy using targeted nanoparticle as drug deliver system to minimize the drug resistance in human cancers. (Supported by NCI P50 CA128613 and U54CA119338–04) 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 LB-196. doi:10.1158/1538-7445.AM2011-LB-196

Abstract B32: TGF-β blockade improves the distribution and efficacy of chemotherapeutic agent in breast carcinoma

Abstract In its journey from blood vessels to cancer cells, a therapeutic agent must overcome the transport barrier posed by the interstitial matrix. In contrast to our understanding of blood vessels, our understanding of the formation and function of the tumor interstitial matrix is still in its infancy. A primary component of the interstitial matrix, collagen type I, has been shown to inversely correlate with diffusive transport in solid tumors. TGF-β can stimulate production of collagen by stromal cells in tumors. Thus, we studied the effect of blocking TGF-β pathway in breast carcinoma progression and response to chemotherapy. To this end, we used a soluble Fc:TGF-β type II receptor fusion protein (sTβRII) to block TGF-β pathway in two breast cancer models (human MDA-MB-231 cells and mouse 4T1 cells). TGF-β blockade significantly impaired the growth and metastasis of orthotopic tumors in both tumor models. The recruitment of myofibroblasts and interstitial matrix content was determined by immunohistochemistry, TGF-β blockade significantly decreased the recruitment of myofibroblast and the level of collagen I. Next, to determine the effect of TGF-β blockade on interstitial transport, we injected fluorescent doxorubicin into the tail vein of mice and observed the intratumoral distribution of doxorubicin autofluorescence by confocal microscopy. We found that TGF-β blockade increased the transvascular flux of fluorescent doxorubicin. As a result, doxorubicin liposome (DOXIL) treatment was significantly more effective in inhibiting tumor progression in TGF-β blocked tumors compared to parental tumors. In summary, our study characterized the functional role of TGF-β in modulating tumor interstitial matrix in breast cancer xenografts and suggested that blocking TGF-β signaling pathway may represent a testable therapeutic approach to be combined with conventional chemotherapy in breast cancer treatment. Citation Information: Clin Cancer Res 2010;16(14 Suppl):B32.

Abstract 4964: Transcriptional repression of MYCN is mediated by TAp63 in human neuroblastomas

Abstract p53 is one of the major tumor suppressors and promotes apoptotic cell death by transcriptional activation of pro-apoptotic target genes. In malignant human tumors, however, its tumor suppressive activity is frequently inactivated by somatic mutation and/or chromosomal deletion. To enhance the efficacy of chemotherapeutic agents in p53-deficient tumors, it is necessary to elucidate the p53-independent mechanisms of apoptotic cell death. Recently, we have shown that TATA-binding protein-like protein (TLP) transactivates one of p53 family members, TAp63, and induces apoptosis in a p53-independent manner. In response to DNA damage by etoposide, TLP is induced to translocate from cytoplasm to nucleus and enhance promoter activity of TAp63 through direct recruitment onto the promoter. TAp63 stimulated by TLP promotes apoptotic cell death in Hep3B cells null for the p53 alleles. The expression levels of TLP mRNA in human primary non-small lung cancers is low compared with corresponding normal tissues and the downregulation is significantly correlated with low levels of TAp63 and poor outcome of patients’ survival. These results suggest the potential for TLP-TAp63 pro-apoptotic pathway as a therapeutic target for malignant lung cancers. In this study, we analyzed expression of p53 family genes in 106 primary neuroblastomas using quantitative real time RT-PCR, and found that the levels of only TAp63 expression was significantly high in favorable neuroblastomas as compared with unfavorable tumors (p=0.00696) and that its expression was inversely correlated with MYCN expression (p=0.0350). MYCN oncogene is frequently amplified and overexpressed in unfavorable neuroblastoma, and in vitro studies have demonstrated that downregulation of MYCN is the critical steps for neuronal cell death induced by retinoic acids (RA) regardless of p53 status in tumors. However, the precise molecular mechanisms of the down-regulation of MYCN by RA have not been elusive. Intriguingly, TLP and TAp63 are induced in response to RA treatment and TAp63 directly represses MYCN transcription. In addition, RA treatment also inhibits positive auto-regulation of MYCN, leading to further down-regulation of MYCN mRNA levels. Collectively, our results suggest that TAp63 is highly expressed in favorable neuroblastomas and contributes to repression of MYCN by RA treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4964.

Abstract 3651: Methylseleninic acid (MSA) is an HDAC inhibitor and suppresses VEGF production in lymphoma cell lines

Abstract Background: Serum selenium (Se) concentration at presentation is prognostic of outcome in patients with aggressive B-cell lymphoma (Last et al., JCO, 2003). We have shown that the Se compound MSA enhanced the efficacy of chemotherapeutic agents at non-cytotoxic concentrations in lymphoma cell lines (Juliger et al., Can Res, 2007). Others have reported that Se enhanced the anti-tumour activity of cytotoxic agents, but reduced toxicity to normal tissue in a xenograft model (Cao et al., Clin Can Res, 2004). In addition, Se has been reported to have antiangiogenic properties including the reduction of tumour microvessel density (Wang et al., Int J Can, 2008). We have therefore investigated the effect of MSA on histone deacetylases (HDACs) and HIF1α, the latter being in part regulated by HDAC activity. Methods: Lymphoma cell lines (RL, SUD4, DHL4) and peripheral blood mononuclear cells (PBMCs) were exposed to MSA in concentration and time-course experiments in normoxic and hypoxic conditions (1% O2). Changes in protein expression were determined by western blotting, HDAC activity measured using an HDAC fluorimetric assay (Biomol), and VEGF levels in cellular supernatants determined using an electrochemiluminescence assay (Meso Scale Discovery). Results: In lymphoma cell lines, exposure to MSA concentrations ≥5μM for 24 hours resulted in acetylation of histone H3 and induction of p21 protein. Acetylation of α-tubulin (mediated by HDAC6, a class II HDAC) occurred to a lesser extent. MSA did not inhibit HDAC activity in an isolated enzyme assay using HeLa cell nuclear extract. However, in whole cells pre-incubated with MSA HDAC activity was inhibited in a concentration-dependent manner. In DHL4 cells, exposure to 10μM and 30μM MSA for 2 hours inhibited HDAC activity by 34% (p=0.01 cf control) and 50% (p=0.02) respectively. 24 hour exposure to MSA concentrations ≥5μM markedly increased histone H3 acetylation in PBMCs. These results suggest that a cellular metabolite of MSA inhibits HDAC activity in intact cells. The effect of MSA on HIF1α expression and VEGF secretion was then investigated. In DHL4 cells, exposure to hypoxia for 24 hours induced HIF1α expression (1.8 fold), an effect not seen in the presence of 20µM MSA. In addition, hypoxia increased VEGF levels to 157% of basal levels, but this was reduced to 43% by 20μM MSA (p=0.007). Conclusions: At clinically relevant concentrations, a cellular metabolite of MSA inhibits HDAC activity and suppresses HIFα induction and VEGF secretion. This effect may account for some of the observed pre-clinical activity with Se species, particularly in animal models. The mechanism of HDAC inhibition is now being investigated. In addition, histone H3 acetylation in PBMCs may serve as a biomarker of Se activity in the clinic. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3651.