Renate Parry

In Vivo Biodistribution, PET Imaging, and Tumor Accumulation of 86Y- and 111In-Antimindin/RG-1, Engineered Antibody Fragments in LNCaP Tumor–Bearing Nude Mice

To optimize in vivo tissue uptake kinetics and clearance of engineered monoclonal antibody (mAb) fragments for radiotherapeutic and radiodiagnostic applications, we compared the biodistribution and tumor localization of four 111In- and 86Y-labeled antibody formats, derived from a single antimindin/RG-1 mAb, in a prostate tumor model. The IgG, diabody, single-chain variable domain (scFv), and novel miniantibody formats, composed of the human IgE-CH4 and a modified IgG1 hinge linked to scFv domains, were compared. Methods: Antibodies were first derivatized with the bifunctional chelator CHX-A″-diethylenetriamine pentaacetic acid and then bound to the radiometal to create radiolabeled immunoconjugates. Human LNCaP xenografts were grown in nude mice, and 111In- or 86Y-labeled antibodies were administered intravenously. Tissues were harvested at different times, and the level of antibody deposition was determined by measuring radioactivity. Whole-body small-animal PET of mice receiving 86Y-labeled antibodies was performed at 6 time points and colocalized with simultaneous micro-CT imaging. Results: The biodistributions of 111In and 86Y antibodies were quite similar. The blood, tumor, kidney, and liver tissues contained varying levels of radioactivity. The antibody accumulation in the tumor correlated with molecular size. The IgG steadily increased with time to 24.1 percentage injected dose per gram (%ID/g) at 48 h. The miniantibody accumulated at a similar rate to reach a lower level (14.2 %ID/g) at 48 h but with a higher tumor-to-blood ratio than the IgG. Tumor accumulation of the diabody peaked at 3 h, reaching a much lower level (3.7 %ID/g). A combination of rapid clearance and lower relative affinity of the scFv precluded deposition in the tumor. Small-animal PET results correlated well with the biodistribution results, with similar tumor localization patterns. Conclusion: The larger antibody formats (IgG and miniantibody) gave higher tumor uptake levels than did the smaller formats (diabody and scFv). These larger formats may be more suitable for radioimmunotherapy applications, evidenced by the preclinical efficacy previously shown by a report on the IgG format. The smaller formats were rapidly cleared from circulation, and the diabody, which accumulated in the tumor, may be more suitable for radiodiagnostic applications.

Identification of a Novel Prostate Tumor Target, Mindin/RG-1, for Antibody-Based Radiotherapy of Prostate Cancer

Gene expression analysis showed that a human mindin homologue, mindin/RG-1, is expressed selectively in prostate tissues and that its expression level is elevated in some prostate tumors. Mindin/RG-1 protein expression is maintained in >80% of prostate cancers metastatic to bone or lymph nodes as well as in locally recurrent tumors in androgen-unresponsive patients. In contrast, mindin/RG-1 expression in other normal tissues is significantly lower than that seen in the prostate. A fully human antibody, 19G9, was generated against mindin/RG-1 protein and was shown to accumulate at high abundance in LNCaP tumor xenografts. Conjugates of this antibody with the chelator CHX-A-DTPA were generated and radiolabeled with either 111In, 90Y, or 86Y. Small animal positron emission tomography imaging with the 86Y-radiolabeled conjugate showed very specific accumulation of the antibody in LNCaP tumor xenografts with clear tumor delineation apparent at 4 hours. The therapeutic efficacy of [90Y]-CHX-A-DTPA-19G9 was evaluated in mice bearing LNCaP xenografts. A dose-finding study identified a nontoxic therapeutic dose to be approximately 75 microCi. Significant antitumor effects were seen with a single administration of radiolabeled antibody to animals bearing 200 to 400 mm3 tumors. Inhibition of tumor growth was observed in all treated animals over a 49-day period. At 49 days posttreatment, slow tumor growth recurred but this could be prevented for an additional 40-day period by a second administration of a 75 microCi dose at day 49. We conclude that [90Y]-CHX-A-DTPA-19G9 is a novel antibody conjugate that has considerable promise for therapy of metastatic prostate cancer in androgen-unresponsive patients.

Targeting tomoregulin for radioimmunotherapy of prostate cancer.

Radiotherapy is an effective approach for the treatment of local prostate cancer. However, once prostate cancer metastasizes, radiotherapy cannot be used due to the distribution of multiple metastases to lymph nodes and bones. In contrast, radioimmunotherapy should still be efficacious in metastatic prostate cancer as radioisotopes are brought to tumor cells by targeting antibodies. Here we identify and validate a prostate-expressed molecule, tomoregulin, as a target for radioimmunotherapy of prostate cancer. Tomoregulin is a transmembrane protein selectively expressed in the brain, prostate, and prostate cancer, but not expressed in other normal tissues. Immunohistochemical studies of tomoregulin protein in clinical samples show its location in the luminal epithelium of normal prostate, benign prostatic hyperplasia, and prostatic intraepithelial neoplasia. More importantly, the tomoregulin protein is expressed in primary prostate tumors and in their lymph node and bone metastases. The nature of tomoregulin as a transmembrane protein and its tissue-specific expression make tomoregulin an attractive target for radioimmunotherapy, in which tomoregulin-specific antibodies will deliver a radioisotope to prostate tumor cells and metastases. Indeed, biodistribution studies using a prostate tumor xenograft model showed that the (111)In-labeled anti-tomoregulin antibody 2H8 specifically recognizes tomoregulin protein in vivo, leading to a strong tumor-specific accumulation of the antibody. In efficacy studies, a single i.p. dose of 150 microCi (163 microg) (90)Y-labeled 2H8 substantially inhibits the growth rate of established LNCaP human prostate tumor xenograft in nude mice but produces no overt toxicity despite cross-reactivity of 2H8 with mouse tomoregulin. Our data clearly validate tomoregulin as a target for radioimmunotherapy of prostate cancer.

Attenuation of the DNA Damage Response by Transforming Growth Factor-Beta Inhibitors Enhances Radiation Sensitivity of Non–Small-Cell Lung Cancer Cells In Vitro and In Vivo

PURPOSEnTo determine whether transforming growth factor (TGF)-β inhibition increases the response to radiation therapy in human and mouse non-small-cell lung carcinoma (NSCLC) cells in vitro and in vivo.nnnMETHODS AND MATERIALSnTGF-β-mediated growth response and pathway activation were examined in human NSCLC NCI-H1299, NCI-H292, and A549 cell lines and murine Lewis lung cancer (LLC) cells. Cells were treated in vitro with LY364947, a small-molecule inhibitor of the TGF-β type 1 receptor kinase, or with the pan-isoform TGF-β neutralizing monoclonal antibody 1D11 before radiation exposure. The DNA damage response was assessed by ataxia telangiectasia mutated (ATM) or Trp53 protein phosphorylation, γH2AX foci formation, or comet assay in irradiated cells. Radiation sensitivity was determined by clonogenic assay. Mice bearing syngeneic subcutaneous LLC tumors were treated with 5 fractions of 6 Gy and/or neutralizing or control antibody.nnnRESULTSnThe NCI-H1299, A549, and LLC NSCLC cell lines pretreated with LY364947 before radiation exposure exhibited compromised DNA damage response, indicated by decreased ATM and p53 phosphorylation, reduced γH2AX foci, and increased radiosensitivity. The NCI-H292 cells were unresponsive. Transforming growth factor-β signaling inhibition in irradiated LLC cells resulted in unresolved DNA damage. Subcutaneous LLC tumors in mice treated with TGF-β neutralizing antibody exhibited fewer γH2AX foci after irradiation and significantly greater tumor growth delay in combination with fractionated radiation.nnnCONCLUSIONSnInhibition of TGF-β before radiation attenuated DNA damage recognition and increased radiosensitivity in most NSCLC cells in vitro and promoted radiation-induced tumor control in vivo. These data support the rationale for concurrent TGF-β inhibition and RT to provide therapeutic benefit in NSCLC.

Poly (ADP-ribose) polymerase inhibitor, an effective radiosensitizer in lung and pancreatic cancers

The development of stereotactic body radiation therapy (SBRT) has revolutionized radiation therapy for lung cancers and is an emerging treatment option for pancreatic cancers. However, there are many questions on how to optimize its use in chemoradiotherapy. The most relevant addition to radiotherapy regimens are inhibitors of DNA repair and DNA damage response pathways. One such class of agents are inhibitors of poly (ADP-ribose) polymerase (PARP). In this study we examined the effects of the PARP inhibitor LT626 in combination with ionizing radiation in lung and pancreatic cancers. Our study demonstrated that combination treatment with LT626 and radiation effectively inhibited growth in lung and pancreatic cancer cell lines, better than individual treatment alone. Combination treatment also increased expression of γH2AX and 53BP1 foci and upregulated expression of phosphorylated ATM, ATR and their respective kinases. Using in vivo lung cancer xenograft models we demonstrated that LT626 functioned as an effective radiosensitizer during fractionated radiation treatment, leading to significant decrease in tumor burden and doubling the median survival compared to control group. Overall our in vitro and in vivo studies showed that PARP inhibitor LT626 acted synergistically with radiation in lung and pancreatic cancers.

Abstract 5490: Poly (ADP-ribose) polymerase inhibitor LT-626 sensitizes lung and pancreatic cancers to fractionated radiation therapy

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CAnnThe development of stereotactic body radiation therapy (SBRT) has revolutionized radiation therapy for lung cancers and is an emerging treatment option for pancreatic cancers. However, there are many questions on how to optimize its use in chemoradiotherapy. The most relevant addition to radiotherapy regimens are inhibitors of DNA repair and DNA damage response pathways. One such class of agents are small-molecule inhibitors of poly (ADP-ribose) polymerase (PARP). PARP inhibitors target DNA base excision repair and radiosensitize cells through impaired DNA repair. In this study we examined the effects of the PARP inhibitor LT-626 (BioMarin) together with ionizing radiation in lung and pancreatic cancers, in vitro and in vivo. Clonogenic assays showed that lung cancer cells H1299 and H460 and pancreatic cancer cells Miapaca2 and PDA were sensitive to LT-626 (IC50 from 0.1-5.8 µM) and irradiation (IC50 from 2.2-5.9 Gy). Next, we found the combination of LT-626 and irradiation effective for inhibiting growth in lung and pancreatic cancer cells. Our study showed that both 1 and 10 µM concentrations of LT-626 were highly synergistic with 2, 4 and 6 Gy of irradiation in lung and pancreatic cell lines. Furthermore, in a fractionated radiation regimen study pretreatment with LT-626 followed by irradiation for three days significantly decreased cell survival as studied by clonogenic assay compared to LT-626 or radiation alone. Lung and pancreatic cancer cells treated with LT-626 and irradiation also exhibited DNA damage as evident by increased γH2AX and Rad51 foci formation. However, DNA damage caused by irradiation peaked by 2-4 h following treatment compared with LT-626 treated cells which exhibited maximum DNA damage around 24 h after treatment. Our in vitro study clearly demonstrated that PARP inhibition enhanced the efficacy of irradiation; we therefore decided to study the efficacy LT-626 and radiation therapy in vivo, using two lung xenograft (H1299 and H460) cancer models. After tumor implantation mice were treated with either drug alone (10mg/kg or 20 mg/kg) or radiation alone (2 Gy) or a combination of drug and radiation for five consecutive days after which they were followed until the end of the study. We found that combination of radiation plus LT-626 significantly decreased tumor burden in both H1299 and H460 xenograft models compared to drug alone or radiation alone group. Moreover, the median survival in combination treated animals more than doubled compared to vehicle treated group. Overall our in vitro and in vivo studies proved that PARP inhibitor LT-626 acts synergistically with fractionated irradiation in lung and pancreatic cancers.nnCitation Format: Kedar Hastak, Lisa McPherson, Yuqiao Shen, Renate Parry, James M. Ford. Poly (ADP-ribose) polymerase inhibitor LT-626 sensitizes lung and pancreatic cancers to fractionated radiation therapy. [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 5490. doi:10.1158/1538-7445.AM2014-5490

Abstract 5715: Modulation of Radiation Response after TGFβ signaling Blockade in Non-small Cell Lung Cancer (NSCLC) Cell Carcinomas

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, ILnnLung cancer remains one of the most prevalent and deadliest malignancies worldwide. Radiotherapy (RT) is a major therapeutic modality for inoperable non-small cell lung cancer (NSCLC). There is substantial evidence that ionizing radiation triggers activation of TGFβ especially in lung, breast and liver tumor. TGFβ inhibition prior to IR inhibits the DNA damage response in epithelial cells via blockade of ATM kinase activity (Cancer Res 62:5627, 2002; Cancer Res 66:10861, 2006) and sensitizes radiation responses in breast cancer cell lines and tumors (Clin Cancer Res 2011;17:6754-6765.). The current studies test whether TGFβ blockade prior to irradiation modulates radiation response of NSCLC cell lines, NCI-H1299, NCI-H292, H460 and Lewis Lung Cancer (LLC), assessed in vitro and in vivo. All NSCLC cell lines responded to TGFβ by phosphorylation of Smad2, which was blocked by LY364947, a small molecule TGFβ type 1 receptor inhibitor. NCI-H1299 and LLC were insensitive to TGFβ growth inhibition in vitro. LY364947 increased radiosensitivity in NCI-H1299 and H460 in clonogenic assays. Consistent with increased clonogenic cell death, TGFβ inhibition also compromised radiation-induced phosphorylation of H2AX and ATM in NCI-H1299. Treatment of cultured LLC cells with either small molecule TGFβ type 1 receptor inhibitor or TGFβ neutralizing antibody, 1D11, significantly increased LLC radiosensitivity as measured by clonogenic assay. Furthermore, C57BL mice bearing subcutaneous LLC tumors treated before and after RT with 1D11 or 13C4 isotype control antibody (20 mg/kg i.p.) resulted in greater tumor growth delay compared to RT and control antibody. Together, these data indicate that TGFβ inhibition prior to radiation attenuates DNA damage responses, enhances clonogenic cell killing, and promotes tumor growth delay. Given the recognized role of radiation-induced TGFβ in lung fibrosis, the therapeutic index for RT could be significantly increased if circumstances are defined in which TGFβ inhibition during RT both enhances lung cancer radiosensitivity and protects normal lung.nnCitation 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 5715. doi:1538-7445.AM2012-5715