Abstract 4238: Exploring the therapeutic potential of IR and IGF-1R/IR (co-)targeting in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy. Despite high response rates to platinum based therapies most patients relapse with resistant disease. For these patients novel therapeutic strategies are needed. Hyper-activation of the insulin-like growth factor receptor (IGF-1R) has been implicated in the development, progression and platinum resistance of ovarian cancer. However, targeting the IGF-1R has shown limited clinical benefit. The insulin receptor (IR), highly homologous to the IGF-1R, confers resistance to IGF-1R targeted therapies. Furthermore, in ovarian cancer alternative splicing results in the expression of IR-A & IR-B isoforms, while in normal adult tissues IR-B is the predominant isoform. Therefore targeting the IR or IR-A may be of clinical importance. In this study we determined the therapeutic potential of IR targeting in ovarian cancer.

First, the expression levels of the IR isoforms, IGF-1R and stimulatory ligands IGF-I & II were determined in a panel of ovarian cancers and ovarian cancer cell lines of different histological subtype (endometrioid, clear cell, serous) using RT-PCR. IR isoforms and IGF-1R were expressed in 96% (43/44) and 78% (35/44) of the ovarian cancers compared to 89% (8/9) and 100% (9/9) of the ovarian cancer cell lines. IGF-I and IGF-II were expressed in all the ovarian cancers compared to 11% (1/9) and 0% (0/9) of the ovarian cancer cell lines, indicating the presence of an autocrine loop. In addition, all cell lines showed membrane receptor expression and functional downstream signaling upon IGF-I, IGF-II & insulin, via PI3K as determined by western blot and flow cytometry. Subsequently, we investigated which splicing factors may be involved in the IR alternative splicing. Expression of splicing factors (hnRNPA1A, hnRNA2B1, CELF1, SRSF1, hnRNPH, hnRNPF) were determined by qRT-PCR. However, expression levels did not correlate with IR isoform levels, indicating a more complex regulation of IR splicing. Finally, we determined the effect of IR, IGF-1R and IR/IGF-1R (co-)targeting by S961 (1000nM), MAB391 (20µg) and OSI906 (10µM), respectively on ovarian cancer cell survival by MTT and clonogenic assays. IR inhibition by S961 resulted in a decrease in cell viability up to 40% in 7/9 ovarian cancer cell lines. Preliminary data showed similar results upon IGF-1R/IR inhibition with OSI906. IGF-1R inhibition by MAB391 did not affect cell viability. Furthermore a reduction in clonogenic capacity (75%) by OSI906 is observed in 2/3 ovarian cancer cell lines tested.

In conclusion, in ovarian cancer functional IR and IGF-1R signaling as well as the presence of a possible autocrine loop may contribute to ovarian cancer pathogenesis and progression. Targeting IR signaling with the IR-antagonist S961 and co-targeting IR/IGF-1R signaling by OSI906 reduced ovarian cancer cell viability, indicating its therapeutic potential in ovarian cancer.

Funded by the Dutch Cancer Foundation: Grant RUG 2011-5231

Citation Format: Jolanda A.L. Visser, Roelien A.M. Meijering, Anne K.L. Reyners, Ate G.J. van der Zee, Steven de Jong. Exploring the therapeutic potential of IR and IGF-1R/IR (co-)targeting in ovarian 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 4238. doi:10.1158/1538-7445.AM2014-4238

Abstract 2417: Predictive and therapeutic impact of DNA damage response activation in locally advanced cervical cancer patients

Recent advances in improving outcome of locally advanced cervical cancer (LACC) were made by addition of cisplatin to radiotherapy. However, total 5-year survival rates are still ∼66%, underscoring the need for new therapy strategies.

Current therapeutic strategies in cervical cancer consist of cisplatin and radiotherapy, which exert their anti-cancer effects by inducing high levels of DNA lesions including DNA double strand breaks (DSBs), with the aim to induce cell death in tumor cells.

However, tumor cells can respond to these therapy-induced DNA lesions by activation of the DNA damage response (DDR). The DDR is a complex signalling network, consisting of multiple kinases and transcriptional programs that function in parallel to arrest ongoing cell cycle progression, which allows time for DNA repair. Effective DNA repair may thus counteracts therapy-induced cancer cell death.

Cervical cancers already have a partial dysfunction of the DDR due to frequent, human papilloma virus (HPV) infection. As a result, HPV-infected cervical tumors are thought to rely heavily on remaining DDR activity for their survival. We therefore hypothesize that the residual DDR activity may provide an ‘Achilles heel’ which could be exploited therapeutically using specific DDR inhibitors, to increase tumor cell sensitivity to cisplatin and ionizing radiation.

Firstly, we examined the expression and activation status of the key DDR components ATM, Chk2, ATR, Chk1, DNA-PK and MK2 in 375 cervical cancer patients using immunohistochemistry. We found that these DDR components were all abundantly expressed in cervical cancer tissues, underscoring the availability of these components for targeting by DDR inhibitors.

Subsequently, we tested chemo- or radiosensitization of specific chemical inhibitors against ATM (KU-55933), ATR (NU-6027), DNA-PK (KU-0060648), Chk1/2 (AZD7762) and MK2 (MK2-inhibitor III) using HPV-positive cervical cancer cell lines HeLa and SiHa. MTT-assay analyses showed that ATR, Chk1/2 and DNA-PK inhibition, sensitized cervical cancer cells to cisplatin. In contrast, clonogenic survival assays revealed that inhibition of ATM, DNA-PK and Chk1/2 caused radiosensitization. In order to uncover how DDR inactivation is most effective in a combined chemo-radiotherapy setting, we therefore optimised an in vitro ‘combination therapy survival assay’ reflecting the different DNA lesions given in clinical LACC therapy. We showed that targeting of ATM, ATR and Chk1/2 caused effective chemo-radiosensitization of cervical cancer cells.

Our data show that DDR components are abundantly expressed in cervical cancer. Furthermore, we show that targeting of individual DDR kinases has differential effects on chemo- or radiotherapy sensitivity. Finally, we show that ATM, ATR and Chk1/2 inhibition are promising strategies to further improve the efficacy of platinum-based chemoradiation.

Citation Format: Hylke W. Wieringa, Marieke Everts, G.Bea A. Wisman, Ate G.J. van der Zee, Elisabeth G.E. de Vries, Marcel A.T.M. van Vugt. Predictive and therapeutic impact of DNA damage response activation in locally advanced cervical cancer patients. [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 2417. doi:10.1158/1538-7445.AM2014-2417

Abstract 2431: 89Zr-bevacizumab PET as an early biomarker for response to everolimus treatment in an ovarian cancer xenograft model

The mammalian target of rapamycin (mTOR) pathway is activated in the majority of ovarian cancers and is involved in tumor angiogenesis. Inhibitors of mTOR, like everolimus, are potentially interesting drugs as they can exert antitumor activity in part through reducing downstream vascular endothelial growth factor-A (VEGF-A) production. We investigated whether early effects of everolimus treatment could be monitored with 89Zr-bevacizumab positron emission tomography (VEGF-PET). Methods: The effect of everolimus on VEGF-A secretion was determined in three human ovarian cancer cell lines and in A2780luc+ ovarian cancer cells xenografted subcutaneously in BALB/c mice. Mice received daily everolimus (10 mg/kg intraperitoneally) for 14 days. PET scans with the tracer 89Zr-labeled bevacizumab were performed to monitor tumor VEGF-A expression before (baseline) and after treatment. Images were obtained 6 days after tracer injection. Tracer uptake was quantified and expressed as mean standardized uptake values (SUVmean). For ex vivo 89Zr-bevacizumab biodistribution and correlative tissue analyses, control animals were sacrificed after the baseline scans. Tumor VEGF-A levels were measured with ELISA in tumor lysates and mean vascular density (MVD) was determined with immunohistochemistry. Results: Everolimus treatment lowered VEGF-A levels in the supernatant of all cell lines. Everolimus lowered 89Zr-bevacizumab tumor uptake by 21.7 ± 4.0% (SUVmean 2.26 ± 0.18 versus 2.89 ± 0.20, p < 0.01). Ex vivo 89Zr-bevacizumab biodistribution showed less tracer uptake in the tumors of treated compared to control animals (7.78 ± 0.84 %ID/g versus 14.02 ± 1.68 %ID/g, p < 0.01), while no differences were observed for other tissues. VEGF-A protein levels in tumor lysates were lower in treated versus untreated tumors (p = 0.04), as was the MVD (p < 0.01). Conclusion: 89Zr-bevacizumab PET showed reduced tumor VEGF-A levels in vivo in response to everolimus therapy, coinciding with inhibition of tumor angiogenesis. Currently there are 2 clinical trials ongoing to study the value of 89Zr-bevacizumab PET to monitor tumor VEGF-A levels as an early biomarker of response to mTOR inhibitor therapy.

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 2431. doi:1538-7445.AM2012-2431

Abstract 4035: Inactivation of the putative tumor suppressor gene AGTR1 by promoter hypermethylation in primary human cancer

Introduction: Primary human cancers are thought to arise from genetic and epigenetic alterations of tumor suppressor genes and oncogenes. Transcriptional and DNA copy-number studies have improved our understanding and classification of solid tumors. Recent studies have established that like mutation, methylation-mediated gene silencing often leads to tumorigenesis. The aim of this study was to comprehensively explore the “ovarian cancer methylome” and to validate the novel methylation marker AGTR1 in a large independent series of ovarian cancer samples. Patients and methods: Fifteen ovarian cancer samples and 10 normal ovarian surface epithelium brushings were hybridized to Affymetrix U133 plus 2.0 arrays. Furthermore, 3 normal ovarian and 3 isogenic (resistant and sensitive to chemotherapy) ovarian cancer cell lines, with or without treatment with a demethylating agent were hybridized to the same array. Selection of cancer specific methylated genes was based on differential expression between normal and cancer samples, with cancer samples having lower expression than normal samples, and upregulation in cancer cell lines after treatment with a demethylating agent. A number of selected genes that showed low or no expression in primary cancer tissues and re-expressed after treatment with a demethylating agent were then tested for promoter methylation by bisulfite sequencing. Quantitative methylation specific PCR (QMSP) was developed for the AGRT1 gene and tested in a total of 353 ovarian cancer, 17 ovarian cystadenoma and 16 ovarian borderline tumor samples. Results: Fourteen primary ovarian tumor DNA samples were available from the samples that were hybridized for expression array analysis. Twelve out of 14 samples were methylated for AGRT1 which is inversely correlated with expression from our array analysis. We then tested 13 normal ovarian epithelium samples and no methylation was detected in any of the samples. Validation in a large independent set of samples confirmed that ovarian cancer samples (207/353, 53%) were more frequently methylated than ovarian cystadenoma (3/17, 18%; P=0.004). Conclusion: We have identified a set of potential tumor suppressor genes by a comprehensive discovery approach to uncover the cancer methylome. Among these genes, AGTR1 methylation was identified as a potential cancer specific methylated gene that may hold promise for further studies to establish it as a biomarker. Functional studies are warranted to evaluate the biologic role of AGTR1 methylation in the carcinogenic process of solid tumors.

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 4035. doi:1538-7445.AM2012-4035

Abstract 3641: The predictive and prognostic roles of DNA damage response genes in epithelial ovarian cancer

Background: Despite platinum-based chemotherapy, 5-year survival of advanced stage ovarian cancer patients is only 15-30%. Exposure to platinum-based chemotherapeutics induces double strand DNA breaks (DSBs) and subsequently leads to activation of the DNA damage response (DDR). Therefore inhibition of components of the DDR may lead to better response to therapy. Aim of this study was to investigate in a large series of ovarian cancer patients the predictive and prognostic role of the activation status of four DDR-proteins- ATM, a key controller in the DDR, and three ATM substrates, including Chk2, 53BP1 and γ-H2AX, of which the latter is a direct readout for DNA damage. Methods: Expression of phospho-ATM, Chk2, phospho-Chk2, 53BP1, phospho-53BP1 and γ-H2AX was immunohistochemically assessed in 309 patients with chemo-naive ovarian cancer. Expression levels were related to clinicopathological characteristics and survival. Response to platinum-based chemotherapy was analyzed by defining two populations with either an optimal therapy response or a very poor therapy response. Both groups consisted of patients with advanced stage ovarian cancer, >2 cm residual disease after primary surgery and were all treated with platinum-based chemotherapy. The responder group had a well-defined PFS of more than 18 months while the non-responder group had a PFS of less than 6 months. Results: In the two well-defined groups with the largest contrast regarding response to treatment, positive γ-H2AX expression (OR=0.193; p=0.036) and positive Chk2 expression (OR=0.149; p=0.011) were related to a good response to platinum-based chemotherapy. In advanced stage patients, phospho-53BP1 expression was independently related to a worse disease-specific survival (HR=1.905; p= 0.044). Conclusion: High DDR protein expression in advanced stage ovarian cancers suggests a high degree of genomic instability, while the negative prognostic impact of phospho-53BP1 may be due to enhanced repair capacity of chemotherapy-induced DSBs on the long term.

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 3641. doi:1538-7445.AM2012-3641

Detecting Cervical Cancer by Quantitative Promoter Hypermethylation Assay on Cervical Scrapings: A Feasibility Study

Current morphology-based cervical cancer screening is associated with significant false-positive and false-negative results. Tumor suppressor gene hypermethylation is frequently present in cervical cancer. It is unknown whether a cervical scraping reflects the methylation status of the underlying epithelium, and it is therefore unclear whether quantitative hypermethylation specific PCR (QMSP) on cervical scrapings could be used as a future screening method augmenting the current approach. Cervical scrapings and paired fresh frozen cervical tissue samples were obtained from 53 cervical cancer patients and 45 controls. All scrapings were morphologically scored and analyzed with QMSP for the genes APC, DAPK, MGMT, and GSTP1. To adjust for DNA input, hypermethylation ratios were calculated against DNA levels of a reference gene. Hypermethylation ratios of paired fresh frozen tissue samples and scrapings of cervical cancer patients and controls were strongly related (Spearman correlation coefficient, 0.80 for APC, 0.98 for DAPK, and 0.83 for MGMT; P < 0.001). More cervical cancer patients than controls were DAPK positive (P < 0.001). When cutoff levels for ratios were defined to be above the highest ratio observed in controls, QMSP in cervical scrapings identified 32 (67%) of 48 cervical cancer patients. This feasibility study demonstrates that QMSP on cervical scrapings holds promise as a new diagnostic tool for cervical cancer. The addition of more genes specifically methylated in cervical cancer will further improve the assay.