Decreased Ki67 Staining Research Articles

Palbociclib, a selective CDK4/6 inhibitor, enhances the effect of selumetinib in RAS-driven non-small cell lung cancer

KRAS is one of the most commonly mutated oncogenes in non-small cell lung cancer (NSCLC). Resistance to MEK inhibitor monotherapy develops through a variety of mechanisms. CDK4 was reported to have a synthetic lethal interaction with KRAS. In this study, we demonstrated the combination effects of the MEK inhibitor selumetinib and the CDK4/6 inhibitor palbociclib in RAS-driven NSCLC. In vitro, cell lines with CDKN2A mutations were insensitive to selumetinib. We used siRNA and pharmacologic inhibition of CDK4 and found that the combination of selumetinib and palbociclib synergistically inhibited RAS-driven NSCLC cases with CDKN2A mutations but not those with wild type CDKN2A. The combination treatment potentiated growth inhibition and increased the population of cells in G1 phase. Selumetinib completely inhibited p-ERK but not p-RB. The addition of palbociclib markedly inhibited p-RB and downregulated survivin expression. In vivo, the combination treatment inhibited the growth of NSCLC xenografts, which correlated with decreased levels of p-RB, downregulated survivin and decreased Ki-67 staining. These data suggest that the combination treatment of palbociclib and selumetinib is effective in preclinical models of RAS-driven NSCLC with CDKN2A mutations.

A novel synthetic analogue of ω-3 17,18-epoxyeicosatetraenoic acid activates TNF receptor-1/ASK1/JNK signaling to promote apoptosis in human breast cancer cells.

A saturated analog of the cytochrome P450-mediated ω-3-17,18-epoxide of ω-3-eicosapentaenoic acid (C20E) activated apoptosis in human triple-negative MDA-MB-231 breast cancer cells. This study evaluated the apoptotic mechanism of C20E. Increased cytosolic cytochrome c expression and altered expression of pro- and antiapoptotic B-cell lymphoma-2 proteins indicated activation of the mitochondrial pathway. Caspase-3 activation by C20E was prevented by pharmacological inhibition and silencing of the JNK and p38 MAP kinases (MAPK), upstream MAPK kinases MKK4 and MKK7, and the upstream MAPK kinase kinase apoptosis signal-regulating kinase 1 (ASK1). Silencing of the death receptor TNF receptor 1 (TNFR1), but not Fas, DR4, or DR5, and the adapters TRADD and TNF receptor-associated factor 2, but not Fas-associated death domain, prevented C20E-mediated apoptosis. B-cell lymphoma-2 homology 3-interacting domain death agonist (Bid) cleavage by JNK/p38 MAPK linked the extrinsic and mitochondrial pathways of apoptosis. In further studies, an antibody against the extracellular domain of TNFR1 prevented apoptosis by TNF-α but not C20E. These findings suggest that C20E acts intracellularly at TNFR1 to activate ASK1-MKK4/7-JNK/p38 MAPK signaling and to promote Bid-dependent mitochondrial disruption and apoptosis. In in vivo studies, tumors isolated from C20E-treated nu/nu mice carrying MDA-MB-231 xenografts showed increased TUNEL staining and decreased Ki67 staining, reflecting increased apoptosis and decreased proliferation, respectively. ω-3-Epoxy fatty acids like C20E could be incorporated into treatments for triple-negative breast cancers.-Dyari, H. R. E., Rawling, T., Chen, Y., Sudarmana, W., Bourget, K., Dwyer, J. M., Allison, S. E., Murray, M. A novel synthetic analogue of ω-3 17,18-epoxyeicosatetraenoic acid activates TNF receptor-1/ASK1/JNK signaling to promote apoptosis in human breast cancer cells.

U1 Adaptors Suppress the KRAS-MYC Oncogenic Axis in Human Pancreatic Cancer Xenografts.

Targeting KRAS and MYC has been a tremendous challenge in cancer drug development. Genetic studies in mouse models have validated the efficacy of silencing expression of both KRAS and MYC in mutant KRAS-driven tumors. We investigated the therapeutic potential of a new oligonucleotide-mediated gene silencing technology (U1 Adaptor) targeting KRAS and MYC in pancreatic cancer. Nanoparticles in complex with anti-KRAS U1 Adaptors (U1-KRAS) showed remarkable inhibition of KRAS in different human pancreatic cancer cell lines in vitro and in vivo As a nanoparticle-free approach is far easier to develop into a drug, we refined the formulation of U1 Adaptors by conjugating them to tumor-targeting peptides (iRGD and cRGD). Peptides coupled to fluorescently tagged U1 Adaptors showed selective tumor localization in vivo Efficacy experiments in pancreatic cancer xenograft models showed highly potent (>90%) antitumor activity of both iRGD and (cRGD)2-KRAS Adaptors. U1 Adaptors targeting MYC inhibited pancreatic cancer cell proliferation caused by apoptosis in vitro (40%-70%) and tumor regressions in vivo Comparison of iRGD-conjugated U1 KRAS and U1 MYC Adaptors in vivo revealed a significantly greater degree of cleaved caspase-3 staining and decreased Ki67 staining as compared with controls. There was no significant difference in efficacy between the U1 KRAS and U1 MYC Adaptor groups. Our results validate the value in targeting both KRAS and MYC in pancreatic cancer therapeutics and provide evidence that the U1 Adaptor technology can be successfully translated using a nanoparticle-free delivery system to target two undruggable genes in cancer. Mol Cancer Ther; 16(8); 1445-55. ©2017 AACR.

Inhibition of N-methyl-N-nitrosourea-induced gastric tumorigenesis by Liuwei Dihuang Pill in db/db mice

AIMTo investigate the inhibitory effect of Liuwei Dihuang Pill (LDP) on gastric tumorigenesis induced by N-methyl-N-nitrosourea (MNU) in diabetic mice.METHODSFour-week-old mice were divided into four groups: A, 12 db/m mice treated with MNU and saline, as the non-diabetic control; B, 12 db/db mice treated with MNU and saline, as the diabetic control; C, 12 db/db mice treated with MNU and metformin, as the positive control; and D, 12 db/db mice treated with MNU and LDP. MNU was administrated for 20 wk to induce gastric carcinogenesis. LDP was administrated for 10 wk for improvement of insulin resistance. Body weight and food intake were measured every week. Blood samples were collected for assays of fasting blood glucose, insulin, insulin-like growth factor (IGF)-1, adiponectin and leptin. Stomach tissues were collected for histopathological analysis, immunohistochemical staining of Ki67, quantitative reverse transcription-polymerase chain reaction and western blotting.RESULTSThe incidence of MNU-induced gastric dysplasia was significantly elevated in diabetic (db/db) mice relative to the control (db/m) mice. The incidence of gastric dysplasia was significantly reduced by LDP with suppression of cell proliferation, as demonstrated by a decrease in Ki67 staining. Hyperglycemia, hyperinsulinemia and serum IGF-1 were inhibited by LDP. Expression of IGF-1 and insulin receptor mRNAs was decreased, phosphorylation of IGF-1 receptor and AKT protein was reduced in the stomach tissues by LDP. In addition, adiponectin was increased and leptin was decreased in the serum by LDP.CONCLUSIONLDP decreased risk of gastric dysplasia in type 2 diabetic mice by down-regulation of IGF and insulin activity and correction of adipokines disorders.

Abstract 1303: In vivo analysis of EGFR family signalling as a bypass mechanism in prostate cancer

Abstract Background: Prostate cancers (PCa) rely on androgenic ligands and the androgen receptor (AR) for their growth and survival, making AR inhibition a predominant therapeutic strategy for these tumors. Some prostate tumors however fail this therapy due to ‘bypass’ mechanisms that emerge as a result of prolonged AR targeting. This in vivo study attempted to assess the expression and activation of the epidermal growth factor receptor (EGFR) family (whose role is well-documented in PCa) in response to androgen deprivation therapy (ADT). Methods: Nude mice were implanted (s.c.) with CWR22 tumors (human-patient-derived, androgen-dependent ‘AD’) and its castration-resistant (‘CR’) subline CWR22-Rv1 (relapsed CWR22). Androgen deprivation (i.e. AR inhibition) was achieved by surgical or ‘sham’ castration of mice. Tumors were analyzed (immunohistochemistry/immunoblot) for EGFR/ErbB2/ErbB3/AR proteins and proliferative/apoptotic markers. Results: Castration caused significant tumor regression in AD but not CR tumors. in vitro viability assays demonstrated that castration (mimicked by using charcoal-stripped serum, ‘css’) did not slow down CR cells to the same degree as it did AD cells. At baseline, intratumoral EGFR protein was unchanged in R22 tumors, ErbB2 levels decreased and ErbB3 protein increased in Rv1 tumors. Castration increased ErbB3 but not EGFR or ErbB2 proteins in CWR22 tumors. Phosphorylated forms of these receptors were generally difficult to detect but there was more phosphorylated ErbB3 protein in Rv1 tumors. Downstream of the EGFR family, there was less phosphorylated Erk but not Akt protein in CWR22-Rv1 tumors. Castration decreased Erk protein in AD tumors but increased it in CR tumors. Immunohistochemical quantification revealed that cytoplasmic EGFR and ErbB3 proteins were elevated in CR tumors but reduced in AD tumors. Castration greatly decreased Ki-67 staining in AD but not in CR tumors while the number of TUNEL-positive nuclei and intensity of PARP staining decreased in castrated CR but not in AD tumors. ErbB3 and AR proteins were significantly correlated with DNA damage and proliferation in CWR22 tumors but only nuclear AR levels and proliferation were significantly correlated in CR tumors. Conclusions: We conclude that androgen deprivation therapy may alter EGFR and ErbB3 protein levels and localization in androgen-dependent and castration-resistant tumors. The EGFR family is typically activated at the cell surface hence their presence and activity there, in response to castration, may initiate signalling pathways encouraging tumor cell proliferation and survival. Citation Format: Maitreyee K. Jathal, Thomas M. Steele, Salma Siddiqui, Benjamin A. Mooso, Leandro S. D’Abronzo, Christiana M. Drake, Paramita M. Ghosh. In vivo analysis of EGFR family signalling as a bypass mechanism in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1303.

Molecular and metabolic differences of treatment responders versus nonresponders in a phase 0 clinical trial of metformin in endometrial cancer

Objectives: In a phase 0 clinical trial of metformin in endometrial cancer (EC) patients, we previously reported that metformin decreased proliferation in the tumors of the majority of patients enrolled. We aimed to determine molecular and metabolic differences between responders and nonresponders to metformin treatment. Methods: Obese women with endometrioid EC were enrolled. Patients took metformin (850 mg QD) for 1 to 4 weeks before surgical staging. Tissue microarrays (triplicate cores) were constructed from formalin-fixed, paraffin-embedded endometrial biopsy and hysterectomy specimens before and after metformin treatment. Expression of the metformin transporters (OCT1, OCT3, PMAT, MATE1, MATE2), phosphorylated (p)-insulinlike growth factor 1 receptor (IGF1R), p-insulin receptor substrate-1 (IRS1), LKB1, and PTEN were evaluated using immunohistochemistry. Global, untargeted metabolomics was performed on serum samples of EC patients before metformin treatment, using combined GC-MS and LC-MS/MS techniques. Results: Of 20 patients enrolled, 13 (65%) responded to metformin as defined by a significant decrease in Ki-67 staining. In responders, metformin decreased the expression of OCT1 (46%, P = .003), OCT3 (40%, P = .036), PMAT (66%, P = .0019), MATE2 (26%, P = .0017), p-IGF1R (24%, P = .035), LKB1 (36%, P = 0.0015), and PTEN (80%, P = .033) but was not associated with changes in MATE1 or p-IRS1. In nonresponders, metformin treatment was not associated with any changes in these molecular targets. Pretreatment MATE2 expression approached significance in predicting response to metformin (P = .0625). Metabolomic profiling revealed that responders had higher premetformin treatment levels of amino acids, dipeptides, glycolytic intermediates, arachidonic acid, monohydroxy fatty acids and lysolipids compared with nonresponders (P < .05). Conclusions: Treatment response to metformin was associated with decreased expression of OCT1, OCT3, PMAT, and MATE2 transporters as well as metabolically relevant proteins associated with obesity and EC. Baseline metabolic differences were found between responders and nonresponders to metformin that may serve as biomarkers for ongoing clinical trials of metformin in this obesity-driven disease.

Efficacy of the combination of MEK and CDK4/6 inhibitors in vitro and in vivo in KRAS mutant colorectal cancer models.

PurposeThough the efficacy of MEK inhibitors is being investigated in KRAS-mutant colorectal cancers (CRC), early clinical trials of MEK inhibitor monotherapy did not reveal significant antitumor activity. Resistance to MEK inhibitor monotherapy developed through a variety of mechanisms converging in ERK reactivation. Since ERK increases cyclin D expression and increases entry into the cell cycle, we hypothesized that the combination of MEK inhibitors and CDK4/6 inhibitors would have synergistic antitumor activity and cause tumor regression in vivo.ResultsThe combination of MEK and CDK4/6 inhibitors synergistically inhibited cancer cell growth in vitro and caused tumor regression in vivo in cell line and patient-derived xenograft models. Combination therapy markedly decreased levels of phosphorylated ribosomal protein S6 both in vitro and in vivo and decreased Ki67 staining in vivo.Experimental DesignWe performed in vitro proliferation, colony formation, apoptosis, and senescence assays, and Western blots, on a panel of 11 KRAS mutant CRC cell lines treated with the MEK inhibitor MEK162, the CDK4/6 inhibitor palbociclib, or the combination. We also treated 4 KRAS mutant CRC cell line and patient-derived xenografts with the MEK inhibitor trametinib, the CDK4/6 inhibitor palbociclib, or the combination, and performed immunohistochemical and reverse phase protein array analysis.ConclusionsCombined inhibition of both MEK and CDK4/6 is effective in preclinical models of KRAS mutant CRC and justifies a planned phase II clinical trial in patients with refractory KRAS-mutant CRC.Efficacy of the combination of MEK and CDK4/6 inhibitors in vitro and in vivo in KRAS mutant colorectal cancer models.

Evaluating treatment response using DW-MRI and DCE-MRI in trastuzumab responsive and resistant HER2-overexpressing human breast cancer xenografts

We report longitudinal diffusion-weighted magnetic resonance imaging (DW-MRI) and dynamic contrast enhanced (DCE)-MRI (7 T) studies designed to identify functional changes, prior to volume changes, in trastuzumab-sensitive and resistant HER2+ breast cancer xenografts. Athymic mice (N = 33) were subcutaneously implanted with trastuzumab-sensitive (BT474) or trastuzumab-resistant (HR6) breast cancer cells. Tumor-bearing animals were distributed into four groups: BT474 treated and control, HR6 treated and control. DW- and DCE-MRI were conducted at baseline, day 1, and day 4; trastuzumab (10 mg/kg) or saline was administered at baseline and day 3. Animals were sacrificed on day 4 and tumors resected for histology. Voxel-based DW- and DCE-MRI analyses were performed to generate parametric maps of ADC, Ktrans, and ve. On day 1, no differences in tumor size were observed between any of the groups. On day 4, significant differences in tumor size were observed between treated vs. control BT474, treated BT474 vs. treated HR6, and treated vs. control HR6 (P < .0001). On day 1, ve was significantly higher in the BT474 treated group compared to BT474 control (P = .002) and HR6 treated (P = .004). On day 4, ve and Ktrans were significantly higher in the treated BT474 tumors compared to BT474 controls (P = .0007, P = .02, respectively). A significant decrease in Ki67 staining reinforced response in the BT474 treated group compared to BT474 controls (P = .02). This work demonstrated that quantitative MRI biomarkers have the sensitivity to differentiate treatment response in HER2+ tumors prior to changes in tumor size.

Antiproliferative and metabolic effects of metformin in a preoperative window clinical trial for endometrial cancer.

We conducted a preoperative window study of metformin in endometrial cancer (EC) patients and evaluated its antiproliferative, molecular and metabolic effects. Twenty obese women with endometrioid EC were treated with metformin (850 mg) daily for up to 4 weeks prior to surgical staging. Expression of the proliferation marker Ki-67, estrogen receptor (ER), progesterone receptor (PR), adenosine monophosphate-activated protein kinase (AMPK), and downstream targets of the mammalian target of rapamycin (mTOR) pathway were measured by immunohistochemistry. Global, untargeted metabolomics analysis of serum pre- and postmetformin treatment, and matched tumor, was performed. Metformin reduced proliferation by 11.75% (P = 0.008) based on the comparison of pre- and posttreatment endometrial tumors. A total of 65% of patients responded to metformin as defined by a decrease in Ki-67 staining in their endometrial tumors post-treatment. Metformin decreased expression of phosphorylated (p)-AMPK (P = 0.00001), p-Akt (P = 0.0002), p-S6 (51.2%, P = 0.0002), p-4E-BP-1 (P = 0.001), and ER (P = 0.0002) but not PR expression. Metabolomic profiling of serum indicated that responders versus nonresponders to treatment were more sensitive to metformin's effects on induction of lipolysis, which correlated with increased fatty acid oxidation and glycogen metabolism in matched tumors. In conclusion, metformin reduced tumor proliferation in a pre-operative window study in obese EC patients, with dramatic effects on inhibition of the mTOR pathway. Metformin induced a shift in lipid and glycogen metabolism that was more pronounced in the serum and tumors of responders versus nonresponders to treatment.This study provides support for therapeutic clinical trials of metformin in obese patients with EC.

Abstract 1434: Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy, that is very difficult to treat. To date, systemic treatment for PDA, either a single agent or combinations of agents, has shown only modest benefits. Numerous epidemiological studies have reported that metformin (MET), a widely used anti-diabetic drug, provides protective benefits in reducing PDA risk among the diabetic population. Using a stable isotope glucose (GLUC) tracer for dynamic metabolic profiling (SiDMAP), we recently reported that high cholesterol (CHOL) alters the cellular metabolism of MiaPaCa2 (a PDA cell line harboring mutant K-Ras) cells by redirecting glucose-derived acetyl-CoA toward fatty acid (FA) synthesis. This response to MET is depended on the level of intracellular CHOL synthesis. We now performed a SiDMAP study in the LSL-K-RasG12D/+, LSL-Trp53R172H/+, Pdx-1-Cre (KPC) and the LSL-K-RasG12D/+, Pdx-1-Cre (KC) mouse models for PDA, and their wild-type littermates (C57Bl6.129). The mice were treated (or not) with MET (250 mg/kg, i.p. Q5D) and subjected to an Intra Peritoneal GLUC Tolerance Test (IPGTT) pre- and post-MET treatment. The KPC mice with the average tumor volume of 80.83+8.57 mm3 and the KC mice with PanIN lesions (aver. 9 mo old) were put on study. K-Ras mutation, with the presence of the tumor (KPC mice), induced an increase in plasma GLUC production via de novo synthesis by the liver using futile cycling of GLUC derived lactate and pyruvate. MET treatment decreased this flux in mutated (KC) and tumor-bearing animals (KPC), but increased this flux in liver of control mice. MET treatment increased the complete GLUC oxidation into 13CO2 in the pancreas of KC and KPC animals. This indicates that the pancreas in MET-treated animals use less GLUC for RNA, DNA and FA synthesis. For 13CO2 production, we found that tumor growth has to be established; the mutation is not enough to induce changes in this flux. As in plasma, tumor growth increases pancreas lactate production from GLUC. MET treatment dramatically decreased the Warburg effect in the pancreas of mutated (KC) and mutated/tumor-bearing (KPC) mice. Finally, MET decreased GLUC-derived acetyl-CoA delivery to FAS and palmitate in control, mutated and tumor-bearing mice. Immunohistochemical analysis of the tumors from the KPC mice revealed that treatment with MET decreased the staining of phospho-Ser79-ACC by ∼54%, total FAS staining (mainly in the tumor stroma) by ∼43%, and the growth-associated transcription factor HMGA2 by ∼36.7%. These decreases correlated with a decrease in Ki67 staining by almost 80%, indicative of an inhibitory effect of MET on PDA growth. These results suggest that mutant K-Ras is responsible for the metabolic adaptation in both the tumor- (KPC) and non-tumor-bearing animals (KC). Our findings provide a strong rationale for targeting the metabolic changes induced by activated K-RAS in PDA patients which harbor mutations in K-RAS gene in &amp;gt;95% of cases. Citation Format: Mary Jo Cantoria, Laszlo G. Boros, Hitendra Patel, Haiyong Han, Natalia Ignatenko, Emmanuelle J. Meuillet. Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic 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 1434. doi:10.1158/1538-7445.AM2014-1434

Subverting ER-stress towards apoptosis by nelfinavir and curcumin coexposure augments docetaxel efficacy in castration resistant prostate cancer cells.

Despite its side-effects, docetaxel (DTX) remains a first-line treatment against castration resistant prostate cancer (CRPC). Therefore, strategies to increase its anti-tumor efficacy and decrease its side effects are critically needed. Targeting of the constitutive endoplasmic reticulum (ER) stress in cancer cells is being investigated as a chemosensitization approach. We hypothesized that the simultaneous induction of ER-stress and suppression of PI3K/AKT survival pathway will be a more effective approach. In a CRPC cell line, C4-2B, we observed significant (p<0.005) enhancement of DTX-induced cytotoxicity following coexposure to thapsigargin and an AKT-inhibitor. However, since these two agents are not clinically approved, we investigated whether a combination of nelfinavir (NFR) and curcumin (CUR), known to target both these metabolic pathways, can similarly increase DTX cytotoxicity in CRPC cells. Within 24 hrs post-exposure to physiologic concentrations of NFR (5 µM) and CUR (5 µM) a significantly (p<0.005) enhanced cytotoxicity was evident with low concentration of DTX (10 nM). This 3-drug combination rapidly increased apoptosis in aggressive C4-2B cells, but not in RWPE-1 cells or in primary prostate epithelial cells (PrEC). Comparative molecular studies revealed that this 3-drug combination caused a more pronounced suppression of phosphorylated-AKT and higher induction in phosphorylated-eIF2α in C4-2B cells, as compared to RWPE-1 cells. Acute exposure (3–9 hrs) to this 3-drug combination intensified ER-stress induced pro-apoptotic markers, i.e. ATF4, CHOP, and TRIB3. At much lower concentrations, chronic (3 wks) exposures to these three agents drastically reduced colony forming units (CFU) by C4-2B cells. In vivo studies using mice containing C4-2B tumor xenografts showed significant (p<0.05) enhancement of DTX’s (10 mg/kg) anti-tumor efficacy following coexposure to NFR (20 mg/kg) & CUR (100 mg/kg). Immunohistochemical (IHC) analyses of tumor sections indicated decreased Ki-67 staining and increased TUNEL intensity in mice exposed to the 3-drug combination. Therefore, subverting ER-stress towards apoptosis using adjuvant therapy with NFR and CUR can chemosensitize the CRPC cells to DTX therapy.

Axitinib Improves Radiotherapy in Murine Xenograft Lung Tumors

A third of patients with non-small cell lung cancer (NSCLC) present with un-resectable stage III locally advanced disease and are currently treated by chemo-radiotherapy but the median survival is only about 21months. Using an orthotopic xenograft model of lung carcinoma, we have investigated the combination of radiotherapy with the anti-angiogenic drug axitinib (AG-013736, Pfizer), which is a small molecule receptor tyrosine kinase inhibitor that selectively targets the signal transduction induced by VEGF binding to VEGFR receptors. We have tested the combination of axitinib with radiotherapy in nude mice bearing human NSCLC A549 lung tumors. The therapy effect was quantitatively evaluated in lung tumor nodules. The modulation of radiation-induced pneumonitis, vascular damage and fibrosis by axitinib was assessed in lung tissue. Lung irradiation combined with long-term axitinib treatment was safe resulting in minimal weight loss and no vascular injury in heart, liver and kidney tissues. A significant decrease in the size of lung tumor nodules was observed with either axitinib or radiation, associated with a decrease in Ki-67 staining and a heavy infiltration of inflammatory cells in tumor nodules. The lungs of mice treated with radiation and axitinib showed a complete response with no detectable residual tumor nodules. A decrease in pneumonitis, vascular damage and fibrosis were observed in lung tissues from mice treated with radiation and axitinib. Our studies suggest that axitinib is a potent and safe drug to use in conjunction with radiotherapy for lung cancer that could also act as a radioprotector for lung tissue by reducing pneumonitis and fibrosis.

Role of endothelin B receptor in oligodendroglioma proliferation and survival: In vitro and in vivo evidence

In this study, the role of the endothelinB receptor (ETBR) in oligodendroglioma cell proliferation and survival was investigated invitro and invivo. The overexpression and knockdown of ETBR was conducted in Hs683 human oligodendroglioma cells, and cell proliferation and activation (phosphorylation) of extracellular signal-regulated kinase (ERK) were measured invitro. An orthotopic xenograft oligodendroglioma mouse model was established. Mouse survival times and immunohistochemical Ki67 staining in the xenografts were examined. Invitro experiments demonstrated that the overexpression of ETBR significantly enhanced the proliferation of oligodendroglioma cells and the activation of ERK compared with the controls, which was eliminated by the selective ETBR inhibitor BQ788 and ERK-specific inhibitor U0126, but not selective endothelinA receptor inhibitor BQ123. By contrast, the knockdown of endogenous ETBR markedly decreased oligodendroglioma cell proliferation and the activation of ERK compared with the controls. Overexpression of ETBR significantly increased immunohistochemical Ki67 staining in the Hs683 cell orthotopic xenograft and decreased animal survival. By contrast, knockdown of ETBR significantly decreased Ki67 staining and increased mouse survival times. Intratumoral injection of BQ788, but not BQ123, significantly decreased Ki67 staining and prolonged mouse survival times. In conclusion, ETBR was demonstrated to mediate the proliferation of oligodendroglioma cells according to an ERK-dependent mechanism. Using an orthotopic xenograft oligodendroglioma mouse model, it was demonstrated invivo that ETBR promotes oligodendroglioma proliferation and that the selective ETBR antagonist effectively inhibits the proliferation of oligodendroglioma cells and prolongs survival times. This study provides a novel insight into the role of ETBR in oligodendroglioma proliferation and survival, and provides the first invivo evidence that ETBR-specific antagonists are a potential therapeutic alternative for oligodendrogliomas.

Abstract A58: An ovarian patient-derived xenograft model to identify the chemoresistant population

Abstract Introduction: A cornerstone of preclinical ovarian cancer research over the last 30 years has been the use of cell lines both in vitro and in vivo. This resource has underperformed in its ability to identify effective novel therapeutics and evaluate the heterogeneity of an ovarian neoplasm. Developing a patient-derived xenograft (PDX) allows for a comprehensive study of the heterogeneous tumor and potentially the identification of cellular populations responsible for chemoresistance and recurrence, but has not been fully characterized for ovarian cancer. We have developed an ovarian PDX model to demonstrate many important similarities and differences between these and primary patient tumors, and begun to explore its utility in identifying mediators of chemoresistance and personalizing therapy. Methods: Tumors removed from patients undergoing primary tumor reductive surgery were implanted into the subcutaneous flanks of SCID mice. Once a tumor developed, it was expanded into additional mice to propagate a PDX line. Tumors were analyzed for heterogeneity by examination of the tumor initiating cell populations, its stromal content with HLA immunohistochemistry, and proliferation with Ki-67. Cohorts of PDX lines were treated with maximum-tolerated dose of combined carboplatin and paclitaxel or vehicle and response was compared between the PDX and the patient. Chemoresistant PDX lines were generated by treatment with MTD carboplatin and paclitaxel until no evidence of disease (NED), observation until recurrence, and retreatment until fully resistant. RNAseq was conducted comparing treated PDX lines to the untreated PDX lines (n=6 pair) to identify important mediators of chemotherapy resistance. Finally, PDX lines were characterized for defects in homologous recombination (HR) repair with an ex vivo assay, correlating HR status with response to PARP inhibition in vivo. Results: Refinement of xenografting procedures yields an 85% success rate in establishing a PDX. PDX tumors maintain the patient's histology, but the stromal component is replaced by murine cells in the first generation. The xenografts retain primary tumor heterogeneity, at least in expression of putative tumor initiating cells (TIC) (ALDH: 17% vs 19%, CD44: 2.4% vs 5%, CD133 10% vs 3%). However, treatment with chemotherapy significantly increases these populations (ALDH1 increased to 36.1% from 16.2% (p=0.002); CD133 increased to 33.8% from 16.2% (p=0.026), suggesting a role in chemotherapy resistance. The treated PDX tumors showed a decrease in Ki67 staining (from 64% to 34%, p=0.001), suggesting dormancy is induced in the surviving population. The PDX tumors show similar response to chemotherapy as patient tumors, in that PDX tumors from patients with a partial response respond more slowly (if at all) than those from patients achieving a complete response (mean change in tumor volume -5.11% vs -63.73%, p=0.029). RNAseq comparing treated and untreated PDX lines indicate only 54 common genes with a significant change in mRNA (p&amp;lt;0.05), suggesting great heterogeneity among patients not only in primary tumor content, but also mediators of chemoresistance. Finally, patient tumors predicted to respond to PARP inhibition by an ex vivo assay show regression of tumor or stable disease with single-agent PARP inhibitor therapy. Conclusions: The ovarian PDX model recapitulates patient tumor heterogeneity and mirrors response to chemotherapy. This model may prove superior in predicting response to therapy in patients, and allows a better model to study complex tumor biology that is impacted by tumor heterogeneity, such as survival of small populations with chemotherapy. Citation Format: Zachary C. Dobbin, Ashwini K. Katre, Monjri M. Shah, Britt K. Erickson, Hauping Chen, Ronald D. Alvarez, Michael G. Conner, Dongquan Chen, Charles N. Landen. An ovarian patient-derived xenograft model to identify the chemoresistant population. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A58.

Chemoprevention of Lung Squamous Cell Carcinoma by Ginseng

Ginseng has been used as a medicinal herb to maintain physical vitality for thousands of years, and it has also been shown to be a nonorgan-specific cancer preventive agent by several epidemiologic studies. However, the chemopreventive effects of Korea white ginseng (KWG) in lung squamous cell carcinoma (SCC) have not been tested. In this study, we investigated the chemopreventive activity of KWG in a mouse lung SCC model. N-nitroso-trischloroethylurea (NTCU) was used to induce lung tumors in female Swiss mice, and KWG was given orally. KWG significantly reduced the percentage of lung SCCs from 26.5% in the control group to 9.1% in the KWG group and in the meantime, increased the percentage of normal bronchial and hyperplasia. KWG was also found to greatly reduce squamous cell lung tumor area from an average of 9.4% in control group to 1.5% in the KWG group. Treatment with KWG decreased Ki-67 staining, suggesting that the lung tumor inhibitory effects of KWG were partly through inhibition of proliferation. High-performance liquid chromatography/mass spectrometry identified 10 ginsenosides from KWG extracts, Rb1 and Rd being the most abundant as detected in mouse blood and lung tissue. The tumor inhibitory effects of KWG are mediated by inhibition of activator protein (AP-1), as showed by in vitro study conducted on AP-1/NF-κB-dependent mouse non-small cell lung carcinoma cell lines. Western blotting of lung tissues also indicated that NTCU upregulated AP-1 through phosphorylation of c-jun-NH2-kinase, which was downregulated by KWG in concurrence with its chemoprevention function. These results suggest that KWG could be a potential chemopreventive agent for lung SCC.

Abstract 5006: SOX2 inhibits Wnt driven colon cancer cell proliferation.

Abstract APC mutation/s resulting in aberrant Wnt signaling, initiates intestinal polyposis and drives adenoma to carcinoma progression in human colon. This represents a target for specific therapeutic intervention and has generated extreme interest among the scientific community. However, it is becoming increasingly apparent that though Wnt signaling may cause robust proliferation, it is the quiescent cell population, defined by stem-ness related gene signatures, that evades chemo-radio therapy targeted at rapidly dividing cells, and perpetuates self-renewal ultimately causing relapse at local site and/or recurrence as distant metastases. We report that SOX2, an embryonic stem cell transcription factor, counteracts Wnt driven tumor cell proliferation and maintains quiescence in colo-rectal cancers (CRC). SOX2 expression increases with progressive staging of colon cancer patients. Using colon cancer cell lines transduced with Wnt reporter constructs, we identified distinct sub-populations with varying degrees of Wnt activity and found that SOX2 expression and Wnt activity are mutually exclusive in SW480 primary CRC cell line, but co-expressed in the isogenic SW620 metastatic CRC cell line. Knockdown of SOX2 in SW620 cell increased anchorage independence in vitro and tumor growth in xenograft models. This was accompanied by an increase of cells in S-phase and increased Ki67 index in IHC of xenograft tissue. Over-expression of SOX2 in SW480 cells resulted in decreased colony formation in soft agar and primary tumor growth in mice. Over-expression also caused increased fraction of cells in G0-G1 phase and decreased Ki67 staining in tumor tissue. In SW620 cell line, SOX2 knockdown not only increased basal Wnt activity, but also caused acquisition of Wnt activity in hitherto Wnt negative cells. Intriguingly, over-expression of SOX2 in SW480 cells, reversed the enhanced Wnt activity gained by loss-of-function APC mutation. Experiments conducted with both SOX2 silenced and over-expressed cell lines revealed that SOX2 inhibits phosphorylation of β-catenin at Serine 552 and 675 thereby decreasing its nuclear sequestration and activation. Screening with protein kinase and phosphatase inhibitors identified PHLPP and PHLPPL as candidate genes that are controlled by SOX2 and are responsible for its effects on β-catenin. Western Blot and qPCR analyses showed that SOX2 enhances PHLPP/L expression. Reporter assays demonstrated that SOX2 controls PHLPP/L promoter activity while ChIP assays confirmed binding of SOX2 to various regions of the respective promoters. IHC of SOX2 silenced xenograft tissue showed decreased PHLPP/L and increased pβ-catenin staining while SOX2 over-expression showed reciprocal changes. Our findings delineate the mechanism by which CRC cells suppress Wnt activity thereby maintaining a pool of quiescent cancer cells, and lay the basis for further research to identify and target these cells. Citation Format: Debasish Boral, Man-Tzu Wang, Daotai Nie. SOX2 inhibits Wnt driven colon cancer cell proliferation. [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 5006. doi:10.1158/1538-7445.AM2013-5006

Protein kinase Cδ is required for ErbB2-driven mammary gland tumorigenesis and negatively correlates with prognosis in human breast cancer

Protein kinase C δ (PKCδ) regulates apoptosis in the mammary gland, however, the functional contribution of PKCδ to the development or progression of breast cancer has yet to be determined. Meta-analysis of ErbB2-positive breast cancers shows increased PKCδ expression, and a negative correlation between PKCδ expression and prognosis. Here, we present in-vivo evidence that PKCδ is essential for the development of mammary gland tumors in a ErbB2-overexpressing transgenic mouse model, and in-vitro evidence that PKCδ is required for proliferative signaling downstream of the ErbB2 receptor. Mouse mammary tumor virus (MMTV)-ErbB2 mice lacking PKCδ (δKO) have increased tumor latency compared with MMTV-ErbB2 wild-type (δWT) mice, and the tumors show a dramatic decrease in Ki-67 staining. To explore the relationship between PKCδ and ErbB2-driven proliferation more directly, we used MCF-10A cells engineered to express a synthetic ligand-inducible form of the ErbB2 receptor. Depletion of PKCδ with short hairpin RNA inhibited ligand-induced growth in both two-dimensional (2D) (plastic) and three-dimensional (3D) (Matrigel) culture, and correlated with decreased phosphorylation of the ErbB2 receptor and reduced activation of Src and MAPK/ERK pathways. Similarly, in human breast cancer cell lines in which ErbB2 is overexpressed, depletion of PKCδ suppresses proliferation, Src and ERK activation. PKCδ appears to drive proliferation through the formation of an active ErbB2/PKCδ/Src signaling complex, as depletion of PKCδ disrupts association of Src with the ErbB2 receptor. Taken together, our studies present the first evidence that PKCδ is a critical regulator of ErbB2-mediated tumorigenesis, and suggest further investigation of PKCδ as a target in ErbB2-positive breast cancer.

Phase II trial of the histone deacetylase inhibitor romidepsin in patients with recurrent/metastatic head and neck cancer

Patients with advanced squamous cell carcinoma of the head and neck (SCCHN) have limited treatment options. Inhibition of histone deacetylases (HDACs) represents a novel therapeutic approach warranting additional investigation in solid tumors. A phase II trial of single agent romidepsin, an HDAC inhibitor, was performed in 14 patients with SCCHN who provided consent for pre- and post-therapy samples of accessible tumor, blood and uninvolved oral mucosa. Romidepsin was administered at 13 mg/m(2) as a 4-h intravenous infusion on days 1, 8 and 15 of 28 day cycles, with response assessment by RECIST every 8 weeks. Objective responses were not observed, although 2 heavily pretreated patients had brief clinical disease stabilization. Observed toxicities were expected, including frequent severe fatigue. Immunohistochemical analysis of 7 pre- and post-treatment tumor pairs demonstrated induction of p21(Waf1/Cip1) characteristic of HDAC inhibition, as well as decreased Ki67 staining. Exploratory microarray analyses of mucosal and tumor samples detected changes in gene expression following romidepsin treatment that were most commonly associated with regulation of transcription, cell cycle control, signal transduction, and electron transport. Treatment with romidepsin did not alter the extent of DNA methylation of candidate gene loci (including CDH1 and hMLH1) in SCCHN tumors. Single agent romidepsin has limited activity for the treatment of SCCHN but can effectively achieve tumor-associated HDAC inhibition. Although tolerability of romidepsin in this setting may be limiting, further evaluation of other HDAC inhibitors in combination with active therapies may be justified.

Disruption of a Nuclear NFATc2 Protein Stabilization Loop Confers Breast and Pancreatic Cancer Growth Suppression by Zoledronic Acid

The aminobisphosphonate zoledronic acid has elicited significant attention due to its remarkable anti-tumoral activity, although its detailed mechanism of action remains unclear. Here, we demonstrate the existence of a nuclear GSK-3β-NFATc2 stabilization pathway that promotes breast and pancreatic cancer growth in vitro and in vivo and serves as a bona fide target of zoledronic acid. Specifically, the serine/threonine kinase GSK-3β stabilizes nuclear NFATc2 through phosphorylation of the serine-rich SP2 domain, thus protecting the transcription factor from E3-ubiquitin ligase HDM2-mediated proteolysis. Zoledronic acid disrupts this NFATc2 stabilization pathway through two mechanisms, namely GSK-3β inhibition and induction of HDM2 activity. Upon nuclear accumulation, HDM2 targets unphosphorylated NFATc2 for ubiquitination at acceptor lysine residues Lys-684/Lys-897 and hence labels the factor for subsequent proteasomal degradation. Conversely, mutagenesis-induced constitutive serine phosphorylation (Ser-215, Ser-219, and Ser-223) of the SP2 domain prevents NFATc2 from HDM2-mediated ubiquitination and degradation and consequently rescues cancer cells from growth suppression by zoledronic acid. In conclusion, this study demonstrates a critical role of the GSK-3β-HDM2 signaling loop in the regulation of NFATc2 protein stability and growth promotion and suggests that double targeting of this pathway is responsible, at least to a significant part, for the potent and reliable anti-tumoral effects of zoledronic acid.

316 Functional and molecular MR for breast cancer characterization

We report longitudinal diffusion-weighted magnetic resonance imaging (DW-MRI) and dynamic contrast enhanced (DCE)-MRI (7 T) studies designed to identify functional changes, prior to volume changes, in trastuzumab-sensitive and resistant HER2 + breast cancer xenografts. Athymic mice (N = 33) were subcutaneously implanted with trastuzumab-sensitive (BT474) or trastuzumab-resistant (HR6) breast cancer cells. Tumor-bearing animals were distributed into four groups: BT474 treated and control, HR6 treated and control. DW- and DCE-MRI were conducted at baseline, day 1, and day 4; trastuzumab (10 mg/kg) or saline was administered at baseline and day 3. Animals were sacrificed on day 4 and tumors resected for histology. Voxel-based DW- and DCE-MRI analyses were performed to generate parametric maps of ADC, Ktrans, and ve. On day 1, no differences in tumor size were observed between any of the groups. On day 4, significant differences in tumor size were observed between treated vs. control BT474, treated BT474 vs. treated HR6, and treated vs. control HR6 (P < .0001). On day 1, ve was significantly higher in the BT474 treated group compared to BT474 control (P = .002) and HR6 treated (P = .004). On day 4, ve and Ktrans were significantly higher in the treated BT474 tumors compared to BT474 controls (P = .0007, P = .02, respectively). A significant decrease in Ki67 staining reinforced response in the BT474 treated group compared to BT474 controls (P = .02). This work demonstrated that quantitative MRI biomarkers have the sensitivity to differentiate treatment response in HER2 + tumors prior to changes in tumor size.