Real-time PCR-based assay to quantify the relative amount of human and mouse tissue present in tumor xenografts

<p>Abstract</p> <p>Background</p> <p>Xenograft samples used to test anti-cancer drug efficacies and toxicities in vivo contain an unknown mix of mouse and human cells. Evaluation of drug activity can be confounded by samples containing large amounts of contaminating mouse tissue. We have developed a real-time quantitative polymerase chain reaction (qPCR) assay using TaqMan technology to quantify the amount of mouse tissue that is incorporated into human xenograft samples.</p> <p>Results</p> <p>The forward and reverse primers bind to the same DNA sequence in the human and the mouse genome. Using a set of specially designed fluorescent probes provides species specificity. The linearity and sensitivity of the assay is evaluated using serial dilutions of single species and heterogeneous DNA mixtures. We examined many xenograft samples at various in vivo passages, finding a wide variety of human:mouse DNA ratios. This variation may be influenced by tumor type, number of serial passages in vivo, and even which part of the tumor was collected and used in the assay.</p> <p>Conclusions</p> <p>This novel assay provides an accurate quantitative assessment of human and mouse content in xenograft tumors. This assay can be performed on aberrantly behaving human xenografts, samples used in bioinformatics studies, and periodically for tumor tissue frequently grown by serial passage in vivo.</p

Abstract 5202: Human colon cancer cell lines contain subsets of cells with the capacity to initiate highly prolific clonal growth in soft agar culture and to form transplantable tumor xenografts <i>in vivo</i>

Abstract Various studies underscore the key role of cancer ‘stem cells’ in the initiation of experimental tumor xenografts from cells derived from patient tumor specimens. Implantation of limited numbers of cancer cells – even ‘single cells’ – which exhibit putative cancer ‘stem cell’ markers were reported to form tumors in mice, although several months were required to achieve palpable tumor masses. In the current study we assessed whether established human colon cancer cell lines still possess the functional capacity to initiate tumor formation from ‘single cell’ preparations. Results indicate that each of seven colon cancer cell lines was capable of soft agar colony formation in RPMI-1640 medium containing either 5-10% FBS or 15% serum substitute. Inoculation of 96-well plates by single cell sorting resulted in highly prolific colony formation by a subset of cells derived from each cell line. While the large majority of colonies achieving a size &amp;gt;60μ in diameter exhibited growth arrest within 3 weeks (&amp;lt;&amp;lt;10 cell mass doublings), a minority of clones (&amp;lt;2%) exhibited sustained growth over the course of 3 – 8 weeks. Colony measurements and cell number / colony calculations indicated that these colonies accumulated cells exceeding 10 mass doublings. According to one ‘stem cell’ model of tumor growth (Mackillop et al, JNCI 70: 9-16, 1983), such prolific colony growth is attributed to the self-renewal of cancer ‘stem cells’, whereas limited colony growth is achieved by partially differentiated cells. To assess whether prolific colonies form tumors in vivo, 10 single colonies derived from each colon cancer cell line were implanted into each of 10 athymic nu/nu mice. Testing of 5 tumor models completed to date shows that 75 – 100% (86% overall) of these colonies form tumor xenografts (median times to 700 mg tumor formation ranged from 40 to 72 days). Subsequent in vivo passage of 3 tumor xenografts per cell line resulted in tumor formation in 85 – 92% of host animals (median times ranging from 29 to 67 days). Thus, despite extensive in vitro propagation, a subset of individual cells in each cell line retained the functional capacity to initiate and sustain cancer cell growth in vitro and in vivo. Single cell cloning in soft agar provides an effective means to isolate individual colonies formed by cancer ‘stem cells’ and to propagate human tumor xenografts with modest numbers of tumor cells, host mice, and tumor formation times. The cell surface marker profile and drug sensitivity of prolific colonies are currently under investigation. (Funded in part by NCI Contract No. HHSN261200800001E) 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 5202. doi:10.1158/1538-7445.AM2011-5202</jats:p

Increased antitumor activity of bevacizumab in combination with hypoxia inducible factor-1 inhibition

Inhibition of HIF-1 is an attractive therapeutic strategy to target the tumor microenvironment. However, HIF-1 inhibitors may have limited activity as single agents and combination therapies may be required. We tested the hypothesis that HIF-1 inhibition in a hypoxic stressed tumor microenvironment, which could be generated by administration of antiangiogenic agents, may result in a more pronounced therapeutic effect. The activity of bevacizumab, either alone or in combination with the HIF-1α inhibitor topotecan, was evaluated in U251-HRE xenografts. Tumor tissue was collected at the end of treatment and changes in tumor oxygenation, angiogenesis, proliferation, apoptosis, HIF-1α levels, HIF-1 target genes and DNA damage were evaluated. Bevacizumab decreased microvessel-density and increased intratumor-hypoxia, but did not induce apoptosis. Moreover, bevacizumab alone caused a significant increase of HIF-1-dependent gene expression in tumor tissue. Addition of a low dose of daily topotecan to bevacizumab significantly inhibited tumor growth, relative to mice treated with topotecan or bevacizumab alone (p<0.01). The addition of topotecan to bevacizumab was also associated with profound inhibition of HIF-1 transcriptional activity, significant inhibition of proliferation and induction of apoptosis. Importantly, DNA damage induced by topotecan alone was not augmented by addition of bevacizumab, suggesting that increased cytotoxic activity did not account for the increased anti-tumor effects observed. These results strongly suggest that combination of anti-VEGF antibodies with HIF-1 inhibitors is an attractive therapeutic strategy targeting in the hypoxic tumor microenvironment

F-aza-T-dCyd (NSC801845), a Novel Cytidine Analog, in Comparative Cell Culture and Xenograft Studies with the Clinical Candidates T-dCyd, F-T-dCyd, and Aza-T-dCyd

Abstract In this article, 5-aza-4′-thio-2′-β-fluoro-2′-deoxycytidine (F-aza-T-dCyd, NSC801845), a novel cytidine analog, is first disclosed and compared with T-dCyd, F-T-dCyd, and aza-T-dCyd in cell culture and mouse xenograft studies in HCT-116 human colon carcinoma, OVCAR3 human ovarian carcinoma, NCI-H23 human NSCLC carcinoma, HL-60 human leukemia, and the PDX BL0382 bladder carcinoma. In three of five xenograft lines (HCT-116, HL-60, and BL-0382), F-aza-T-dCyd was more efficacious than aza-T-dCyd. Comparable activity was observed for these two agents against the NCI-H23 and OVCAR3 xenografts. In the HCT-116 study, F-aza-T-dCyd [10 mg/kg intraperitoneal (i.p.), QDx5 for four cycles], produced complete regression of the tumors in all mice with a response that proved durable beyond postimplant day 150 (129 days after the last dose). Similarly, complete tumor regression was observed in the HL-60 leukemia xenograft when mice were dosed with F-aza-T-dCyd (10 mg/kg i.p., QDx5 for three cycles). In the PDX BL-0382 bladder study, both oral and i.p. dosing of F-aza-T-dCyd (8 mg/kg QDx5 for three cycles) produced regressions that showed tumor regrowth beginning 13 days after dosing. These findings indicate that further development of F-aza-T-dCyd (NSC801845) is warranted. </jats:sec

Development and Validation of an Immunoassay for Quantification of Topoisomerase I in Solid Tumor Tissues

BACKGROUND: Topoisomerase I (Top1) is a proven target for cancer therapeutics. Recent data from the Fluorouracil, Oxaliplatin, CPT-11: Use and Sequencing (FOCUS) trial demonstrated that nuclear staining of Top1 correlates with chemotherapeutic efficacy. Such a correlation may help identify patients likely to respond to Top1 inhibitors and illuminate their mechanism of action. Cellular response to Top1 inhibitors is complex, but Top1 target engagement is a necessary first step in this process. This paper reports the development and validation of a quantitative immunoassay for Top1 in tumors. METHODOLOGY/PRINCIPAL FINDINGS: We have developed and validated a two-site enzyme chemiluminescent immunoassay for quantifying Top1 levels in tumor biopsies. Analytical validation of the assay established the inter-day coefficient of variation at 9.3%±3.4% and a 96.5%±7.3% assay accuracy. Preclinical fit-for-purpose modeling of topotecan time- and dose-effects was performed using topotecan-responsive and -nonresponsive xenografts in athymic nude mice. Higher baseline levels of Top1 were observed in topotecan-responsive than -nonresponsive tumors. Top1 levels reached a maximal decrease 4 to 7 hours following treatment of engrafted mice with topotecan and the indenoisoquinoline NSC 724998. CONCLUSIONS/SIGNIFICANCE: Our analysis of Top1 levels in control and treated tumors supports the previously proposed mechanism of action for Top1 inhibitor efficacy, wherein higher baseline Top1 levels lead to formation of more covalent-complex-dependent double-strand break damage and, ultimately, cell death. In contrast, xenografts with lower baseline Top1 levels accumulate fewer double-stand breaks, and may be more resistant to Top1 inhibitors. Our results support further investigation into the use of Top1 levels in tumors as a potential predictive biomarker. The Top1 immunoassay described in this paper has been incorporated into a Phase I clinical trial at the National Cancer Institute to assess pharmacodynamic response in tumor biopsies and determine whether baseline Top1 levels are predictive of response to indenoisoquinoline Top1 inhibitors

Supplementary Figure S1 from F-aza-T-dCyd (NSC801845), a Novel Cytidine Analog, in Comparative Cell Culture and Xenograft Studies with the Clinical Candidates T-dCyd, F-T-dCyd, and Aza-T-dCyd

Supplementary Figure S1</p

Abstract 5082: Impact of HGF knockin microenvironment on epithelial-mesenchymal transition and cancer stem cells in a non-small cell lung cancer xenograft model

Abstract We previously reported the generation of rabbit monoclonal antibodies to twelve EMT (epithelial-to-mesenchymal transition) transcription factors and cancer stem cell (CSC) markers for the development of pharmacodynamic assays to inform clinical trials of new anticancer therapies (Pfister et al., AACR 2013). Here we demonstrate the functional utility of some of these reagents in detecting HGF-induced changes in EMT and CSC biology in a xenograft tumor model. Initial antibody characterization was performed in vitro and a subset [including SNAIL, SLUG, SOX9, Goosecoid (GSC), NANOG and CD133] was selected for further testing of functional utility in FFPE tissues by quantitative multiplex IFA. The antibodies were applied to xenograft tissues derived from the non-small cell lung cancer tumor line, NCI-H596, implanted in hHGFscid/scid, hHGFki/scid or hHGFki/ki mice to examine HGF-induced changes in EMT factors, CSC markers, as well as pY1235-MET expression in vivo. H596 tumors grown in either hHGFki/scid or hHGFki/ki mice exhibited enhanced EMT particularly in tumor microenvironments adjacent to mouse stroma containing the HGF knockin gene, compared to those in hHGFscid/scid mice. By quantitative immunofluorescence, H596 tumors showed increased Vimentin:E-cadherin ratio when grown in hHGFki/scid (P&amp;lt;0.0006) or hHGFki/ki (P&amp;lt;0.022) vs. HGFscid/scid mice. Moreover, significant increases in nuclear pY1235-MET, measured by%NAP (percentage nuclear area positive), were observed in H596 tumors in hHGFki/scid (P&amp;lt;0.0041) or hHGFki/ki (P&amp;lt;0.0058) vs. hHGFscid/scid. We detected varying levels of EMT/CSC marker expression, including CD44, CD133, ALDH, and GSC in the membrane or cytoplasm of noninvasive regions of H596 tumors in hHGFscid/scid mice. Sox9 was also co-expressed with GSC in some tumor cells but was predominantly in the nuclei. In tissues collected from hHGFki/scid or hHGFki/ki mice, Slug, Snail and Sox9 expression were increased in transitioning tissue regions, adjacent to HGF-containing stroma, coincident with diminished E-Cadherin expression and enhanced Vimentin expression. While Slug expression was predominantly cytoplasmic in invading tumor fronts, the expression was mutually exclusive with CD133 within non-invasive regions. Snail and Sox9 showed enhanced nuclear expression in tumor cells undergoing EMT. These markers are currently being investigated in additional tumor samples from human TNBC or CRC xenograft models treated with various drug combinations. To our knowledge, this is the first demonstration of EMT and changes in cancer stem cell biology in NSCLC induced by an HGF-knockin stromal microenvironment. Funded by NCI Contract No. HHSN261200800001E. Citation Format: Tony Navas, Thomas D. Pfister, Scott M. Lawrence, Apurva K. Srivastava, Robert J. Kinders, Suzanne Borgel, Sergio Alcoser, Melinda G. Hollingshead, Lindsay M. Dutko, Brad A. Gouker, Donna Butcher, Elinor Ng-Eaton, Naoko Takebe, Young H. Lee, Donald P. Bottaro, Ralph E. Parchment, Joseph E. Tomaszewski, James H. Doroshow. Impact of HGF knockin microenvironment on epithelial-mesenchymal transition and cancer stem cells in a non-small cell lung cancer xenograft model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5082. doi:10.1158/1538-7445.AM2015-5082</jats:p

Supplementary Table T1 from F-aza-T-dCyd (NSC801845), a Novel Cytidine Analog, in Comparative Cell Culture and Xenograft Studies with the Clinical Candidates T-dCyd, F-T-dCyd, and Aza-T-dCyd

Supplementary Table T1</p