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Supplementary Video 4E and F from Selective Targeting and Potent Control of Tumor Growth Using an EphA2/CD3-Bispecific Single-Chain Antibody Construct

Supplementary Video 4I from Selective Targeting and Potent Control of Tumor Growth Using an EphA2/CD3-Bispecific Single-Chain Antibody Construct

The EphA2 receptor tyrosine kinase is frequently overexpressed and functionally altered in malignant cells and thus provides opportunities for selective targeting of tumor cells. We describe here the development of a novel, bispecific single-chain antibody (bscAb) referred to as bscEphA2xCD3. This molecule simultaneously targets EphA2 on tumor cells and the T-cell receptor/CD3 complex on T cells and possesses structural and functional characteristics of the recently developed BiTE technology. An EphA2-specific single-chain antibody was selected for recognition of an epitope that is preferentially exposed on malignant cells based on the concept of epitope exclusion; this was fused to a CD3-specific single-chain antibody to generate bscEphA2xCD3. The resultant bscAb redirected unstimulated human T cells to lyse EphA2-expressing tumor cells both in vitro and in vivo. In separate experiments, efficient tumor cell lysis was achieved in vitro at drug concentrations ≤1 μg/mL, at a low T-cell effector-to-tumor target cell ratio (1:1), and with tumor cells that possess few available binding sites (2,400 per cell) for bscEphA2xCD3. Time-lapsed microscopy revealed potent cytotoxic activity of bscEphA2xCD3-activated T cells against monolayers of malignant cells but not against monolayers of nontransformed EphA2-positive cells except at the edges of the monolayer where the target epitope was exposed. BscEphA2xCD3 was also efficacious in human xenograft mouse models modified to show human T-cell killing of tumors. Together, our results reveal opportunities for redirecting the potent activity of cytotoxic T cells towards tumor cells that express selectively accessible epitopes and establish EphA2-specific bscAb molecules as novel and potent therapeutics with selectivity for tumor cells. [Cancer Res 2007;67(8):3927–35]

Supplementary Video 4A and B from Selective Targeting and Potent Control of Tumor Growth Using an EphA2/CD3-Bispecific Single-Chain Antibody Construct

Supplementary Video 4G and H from Selective Targeting and Potent Control of Tumor Growth Using an EphA2/CD3-Bispecific Single-Chain Antibody Construct

Supplementary Video 4C and D from Selective Targeting and Potent Control of Tumor Growth Using an EphA2/CD3-Bispecific Single-Chain Antibody Construct

We have developed a novel single-chain Ep-CAM-/CD3-bispecific single-chain antibody construct designated MT110. MT110 redirected unstimulated human peripheral T cells to induce the specific lysis of every Ep-CAM-expressing tumor cell line tested. MT110 induced a costimulation independent polyclonal activation of CD4- and CD8-positive T cells as seen by de novo expression of CD69 and CD25, and secretion of interferon gamma, tumor necrosis factor alpha, and interleukins 2, 4 and 10. CD8-positive T cells made the major contribution to redirected tumor cell lysis by MT110. With a delay, CD4-positive cells could also contribute presumably as consequence of a dramatic upregulation of granzyme B expression. MT110 was highly efficacious in a NOD/SCID mouse model with subcutaneously growing SW480 human colon cancer cells. Five daily doses of 1 microg MT110 on days 0-4 completely prevented tumor outgrowth in all mice treated. The bispecific antibody construct also led to a durable eradication of established tumors in all mice treated with 1 microg doses of MT110 on days 8-12 after tumor inoculation. Finally, MT110 could eradicate patient-derived metastatic ovarian cancer tissue growing under the skin of NOD/SCID mice. MT110 appears as an attractive bispecific antibody candidate for treatment of human Ep-CAM-overexpressing carcinomas.

Bispecific T-cell engager (BiTE) are a class of bispecific single-chain antibodies that can very effectively redirect cytotoxic T cells for killing of tumor target cells. Here, we have assessed the in vivo efficacy of one representative, called bscEp-CAMxCD3, with specificity for tumors overexpressing epithelial cell adhesion molecule (Ep-CAM) in human xenograft models. Cells of the human colon carcinoma line SW480 were mixed at a 1:1 ratio with unstimulated human peripheral mononuclear cells, s.c. injected in nonobese diabetes/severe combined immunodeficiency (NOD/SCID) mice, and animals were treated with bscEp-CAMxCD3. Five daily i.v. injections of as little as 100 ng per mouse of bscEp-CAMxCD3 completely prevented tumor outgrowth when treatment was started at the day of tumor cell inoculation. BscEp-CAMxCD3 was also efficacious when administered up to 8 days after xenograft injection. Established tumors could be eradicated in all animals by five 10 μg doses given between days 8 and 12 after tumor cell inoculation. To test the efficacy of bscEp-CAMxCD3 in a more physiologic model, pieces of primary metastatic tumor tissue from ovarian cancer patients were implanted in NOD/SCID mice. Partial tumor engraftment and growth was observed with four of six patient samples. Treatment of established tumors with daily 5 μg doses led to a significant reduction and, in some cases, eradication of human tumor tissue. These effects obviously relied on the tumor-resident T cells reactivated by bscEp-CAMxCD3. Our data show that the class of single-chain bispecific antibodies has very high antitumor efficacy in vivo and can use previously unstimulated T cells at low effector-to-target ratios.

Bispecific T cell engager (BiTE®) antibody constructs redirect T cells to induce lysis of tumor cells. The anti-CD19/CD3 BiTE® Blincyto® can deplete target cells in both the blood and tissue compartment in B cell malignancies, suggesting that the BiTE® mechanism of action will also be effective against solid tumors. The tumor differentiation antigen mesothelin (MSLN) is an attractive target for the BiTE® approach. MSLN is highly expressed in >80% of ovarian and pancreatic tumors and mesothelioma. Expression of MSLN in normal tissues appears restricted to mesothelial cell surfaces such as the pleural, pericardial, and peritoneal layer. Here, we report the preclinical characterization of an anti-MSLN/CD3 BiTE® antibody construct with extended half-life. The BiTE® antibody construct binds MSLN and CD3 with low nM affinity and has low pM cytotoxic activity against MSLN-positive ovarian, pancreatic and lung cancer cell lines in vitro. Activity of the anti-MSLN/CD3 BiTE® antibody construct is observed at low effector to target cell ratios, and in cancer cells that express low levels of MSLN. This BiTE® antibody construct is also cytotoxic to cell lines that are resistant to chemotherapy. In mice, significant tumor growth inhibition of an established ovarian tumor xenograft model was achieved by IV dosing of the anti-MSLN/CD3 BiTE® antibody construct every 5 days. Pharmacokinetic evaluation of the anti-MSLN/CD3 BiTE® antibody construct in non-human primates demonstrated a half-life of 4-10 days. The potency and specificity of the anti-MSLN/CD3 BiTE® antibody construct, together with projected ability to dose once a week IV in humans, supports development of this BiTE® for treatment of MSLN-positive tumors. Citation Format: Alexander Sternjak, Fei Lee, Joachim Wahl, Dan Rock, Oliver Thomas, Sabine Stienen, Ralf Lutterbuese, Patrick Hoffmann, Tobias Raum, Peter Kufer, Benno Rattel, Angela Coxon, Matthias Friedrich, Julie Bailis. Preclinical evaluation of a BiTE® antibody construct with extended half-life that targets the tumor differentiation marker mesothelin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3630. doi:10.1158/1538-7445.AM2017-3630

T cell engaging bispecific antibody constructs (BiTE®), such as blinatumomab which targets CD19-positive cells, have shown great promise for treating certain CD19-positive hematological malignancies. Blinatumomab comprises a single chain Fv (scFv) that binds CD19 and a scFv that targets the T cell CD3 protein. The molecular weight of this “canonical” BiTE® is ~ 55 kDa, making it susceptible to kidney-mediated clearance and resulting in a short serum half-life (~ 4 hours). To maintain effective serum concentrations, canonical BiTE® antibody constructs must be administered by continuous IV (cIV) infusion. While there are many advantages associated with cIV administration (e.g., safety and uniform PK profile), patient convenience could be enhanced if the BiTE® antibody construct were compatible with once-weekly administration. To achieve this, the serum half-life of the BiTE® antibody construct would need to be extended. A canonical BiTE® targeting CD33 (AMG 330) is currently being evaluated in a phase I clinical trial. Like blinatumomab, AMG 330 is dosed cIV. To extend the serum half-life of AMG 330 and enable once-weekly dosing, several approaches were evaluated including fusion of AMG 330 to human albumin and Fc-containing moieties. Each of these half-life extended (HLE) constructs was evaluated in vitro, in mouse xenograft models and in non-human primates. In vitro assays evaluated 1) binding to both human and cynomolgus CD33 and CD3 proteins, and 2) cytotoxicity using human and cynomolgus target and effector cells. In each of these assays the canonical and HLE BiTE® antibody constructs demonstrated similar activity: single-digit nM binding and single digit pM cytotoxicity. Canonical and HLE BiTE® antibody constructs were subsequently evaluated in an orthotopic mouse model in which MOLM13 cells were administered IV and activated human T cells were administered IP two days later. The Fc-based HLE BiTE® antibody constructs provided a similar survival advantage when administered Q4D or Q5D as the canonical BiTE® when administered QD. However, the albumin fusion–based HLE BiTE® was less efficacious when administered Q4D than the QD- administered canonical BiTE®. Lastly, the PK/PD relationship was evaluated for each of the constructs in non-human primates. The serum half-lives varied from 6 hours for the canonical BiTE® to 44-167 hours for the HLE BiTE® antibody constructs. Each of the HLE BiTE® antibody constructs showed on-target depletion of CD33-positive monocytes and neutrophils in the blood and depletion of CD33-positive cells in the bone marrow. These data demonstrate that half-life extended BiTE® antibody constructs can be generated that retain comparable in vitro and in vivo activity as a canonical BiTE® and achieve a serum half-life compatible with once weekly dosing. Citation Format: Tara L. Arvedson, Mercedesz Balazs, Pamela Bogner, Kurt Black, Kevin Graham, Anja Henn, Matthias Friedrich, Patrick Hoffmann, Roman Kischel, Peter Kufer, Ralf Lutterbuese, Markus Muenz, Tobias Raum, Benno Rattel, Karen Rex, Dan Rock, Oliver Thomas, Joachim Wahl, Andreas Wolf, Angela Coxon. Generation of half-life extended anti-CD33 BiTE® antibody constructs compatible with once-weekly dosing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 55. doi:10.1158/1538-7445.AM2017-55

BiTE® therapeutics are single chain antibody constructs harboring two binding moieties: one directed at a tumor associated antigen and one directed at the CD3e protein, which trigger T cell dependent cellular cytotoxicity (TDCC) against targeted cancer cells. Here, we evaluated the suitability of ENPP3 as a potential BiTE® target. The ENPP3 mRNA is highly differentially expressed in clear cell Renal Cell Carcinoma (ccRCC) and the ENPP3 protein is detected with high uniformity and intensity in ccRCC tumor samples by immunohistochemistry. We demonstrated the surface expression of this protein in Renal Cancer cell lines and confirmed that the ENPP3 protein was highly restricted to the luminal side of normal epithelial layers in which it was detected (proximal renal tubules, bronchial epithelium, salivary glands). We developed highly potent anti-ENPP3 BiTE® molecules and demonstrated the in vitro TDCC activity of these molecules. Two anti-ENPP3 BiTE® molecules further demonstrated tumor formation inhibition activity in a human T cell / human target cell admixture mouse xenograft model. Citation Format: Olivier Nolan-Stevaux, Flordeliza Fajardo, Lily Liu, Suzanne Coberly, Patricia McElroy, Aaron Nazarian, Franziska Bott, Elisabeth Nahrwold, Tobias Raum, Roman Kischel, Ralf Lutterbuese, Patrick Hoffmann, Peter Kufer. Assessing ENPP3 as a renal cancer target for bispecific T-cell engager (BiTE) therapy. [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 585.

Purpose Blinatumomab, a bispecific single-chain antibody targeting the CD19 antigen, is a member of a novel class of antibodies that redirect T cells for selective lysis of tumor cells. In acute lymphoblastic leukemia (ALL), persistence or relapse of minimal residual disease (MRD) after chemotherapy indicates resistance to chemotherapy and results in hematologic relapse. A phase II clinical study was conducted to determine the efficacy of blinatumomab in MRD-positive B-lineage ALL. Patients and Methods Patients with MRD persistence or relapse after induction and consolidation therapy were included. MRD was assessed by quantitative reverse transcriptase polymerase chain reaction for either rearrangements of immunoglobulin or T-cell receptor genes, or specific genetic aberrations. Blinatumomab was administered as a 4-week continuous intravenous infusion at a dose of 15 μg/m2/24 hours. Results Twenty-one patients were treated, of whom 16 patients became MRD negative. One patient was not evaluable due to a grade 3 adverse event leading to treatment discontinuation. Among the 16 responders, 12 patients had been molecularly refractory to previous chemotherapy. Probability for relapse-free survival is 78% at a median follow-up of 405 days. The most frequent grade 3 and 4 adverse event was lymphopenia, which was completely reversible like most other adverse events. Conclusion Blinatumomab is an efficacious and well-tolerated treatment in patients with MRD-positive B-lineage ALL after intensive chemotherapy. T cells engaged by blinatumomab seem capable of eradicating chemotherapy-resistant tumor cells that otherwise cause clinical relapse.

Epidermal growth factor receptor (EGFR)-specific monoclonal antibodies predominantly inhibit colorectal cancer (CRC) growth by interfering with receptor signaling. Recent analyses have shown that patients with CRC with mutated KRAS and BRAF oncogenes do not profit from treatment with such antibodies. Here we have used the binding domains of cetuximab and pantitumumab for constructing T cell-engaging BiTE antibodies. Both EGFR-specific BiTE antibodies mediated potent redirected lysis of KRAS- and BRAF-mutated CRC lines by human T cells at subpicomolar concentrations. The cetuximab-based BiTE antibody also prevented at very low doses growth of tumors from KRAS- and BRAF-mutated human CRC xenografts, whereas cetuximab was not effective. In nonhuman primates, no significant adverse events were observed during treatment for 3 wk at BiTE serum concentrations inducing, within 1 d, complete lysis of EGFR-overexpressing cancer cells. EGFR-specific BiTE antibodies may have potential to treat CRC that does not respond to conventional antibodies.

muS110 is a BiTE antibody bispecific for murine EpCAM (CD326) and murine CD3. MT110, its human-specific analog, is in a clinical phase 1 trial for treatment of patients with adenocarcinoma of the lung or gastrointestinal tract. Recent studies have shown a therapeutic window for muS110, have explored single-dose toxicity of muS110, and have found that a 1-week low-dose treatment dramatically increased the tolerability of mice to very high doses of muS110 (Cancer Immunol. Immunother. 2009;58:95-109). Here we analyzed the impact of long-term, high-dose treatment of mice with muS110 on antitumor activity and functionality of T cells. After an initial self-limiting cytokine release, the 1-week adaptation period effectively blunted further cytokine production in response to a subsequent high-dose treatment with muS110. The much-increased tolerability of mice adapted to muS110 was not because of anergy of T cells. T cells isolated from chronically muS110-treated mice fully retained their cytotoxic potential, proliferative capacity, and responsiveness to stimulation by either muS110 or anti-CD3/anti-CD28/interleukin-2 when compared with T cells from control mice. Unimpaired T-cell performance was also evident from the effective prevention of orthotopic 4T1 breast tumor outgrowth in mice treated long term with escalating doses of muS110. Finally, we show that muS110 and MT110 recognize orthologous epitopes on mouse and human EpCAM proteins, suggesting that the target-related safety profile of muS110 in mice may be predictive for MT110 in humans.

Carcinoembryonic antigen (CEA, CD66e) is a well-characterized tumor-associated antigen that is frequently overexpressed in tumors. Phospholipases release CEA from tumor cells resulting in high circulating serum levels of soluble CEA (sCEA) that has been validated as marker for progression of colorectal, breast, and lung cancers. sCEA also acts as a competitive inhibitor for anticancer strategies targeting membrane-bound CEA. As a novel therapeutic approach for treatment of tumors expressing CEA on their cell surface, we constructed a series of bispecific single-chain antibodies (bscAb) combining various single-chain variable fragments recognizing human CEA with a deimmunized single-chain variable fragments recognizing human CD3. CEA/CD3-bscAbs redirected human T cells to lyse CEA-expressing tumor cells in vitro and in vivo. Efficient tumor cell lysis was achieved in vitro at bscAb concentrations from 1 pg/mL (19 fM) to 8.9 pg/mL with preactivated CD8 T cells, and 200 to 500 pg/mL with unstimulated peripheral blood mononuclear cell. The cytotoxic activity of a subset of CEA/CD3-bscAbs was not competitively inhibited by sCEA at concentrations that exceeded levels found in the serum of most cancer patients. Treatment with CEA/CD3-bscAbs prevented the growth of human colorectal cancer lines in a severe combined immunodeficiency mouse model modified to show human T cell killing of tumors. A murine surrogate CEA/CD3-bscAb capable of recruiting murine T cells for redirected tumor lysis in immunocompetent mice prevented the growth of lung tumors expressing human CEA. Together, our results reveal a unique opportunity for targeting cytotoxic T cells toward CEA-expressing tumors without being competitively inhibited by sCEA and establish CEA/CD3-bscAb as a promising and potent therapeutic approach.

We have compared the cytotoxic activity of rituximab with that of blinatumomab (MT103/MEDI-538), a single-chain CD19-/CD3-bispecific antibody engaging human T cells. Blinatumomab consistently led to a higher degree of lysis of human lymphoma lines than rituximab, and was active at much lower concentration. The cytotoxicity mediated by blinatumomab and rituximab both caused a potent activation of pro-caspases 3 and 7 in target cells, a key event in induction of granzyme-mediated apoptotic cell death. Combination of rituximab with blinatumomab was found to greatly enhance the activity of rituximab, in particular at low effector-to-target cell ratios and at low antibody concentration.

EpCAM (CD326) is one of the most frequently and highly expressed tumor-associated antigens known and recently has also been found on cancer stem cells derived from human breast, colon, prostate, and pancreas tumors. However, like many other tumor-associated antigens used for antibody-based immunotherapeutic approaches, EpCAM is expressed on normal tissues including epithelia of pancreas, colon, lung, bile ducts, and breast. To assess the therapeutic window of an EpCAM/CD3-bispecific single-chain antibody construct of the bispecific T-cell engager (BiTE) class, we constructed murine surrogate of MT110 (muS110) from single-chain antibodies specific for murine EpCAM and CD3 antigens. Immunhistochemical analysis showed that, with minor differences, the expression of EpCAM protein on a large variety of tissues from man and mouse was similar with respect to distribution and level. MuS110 exhibited significant antitumor activity at as low as 5 μg/kg in both syngeneic 4T1 orthotopic breast cancer and CT-26 lung cancer mouse models. Dosing of muS110 for several weeks up to 400 μg/kg by intraanimal dose escalation was still tolerated, indicating existence of a significant therapeutic window for an EpCAM-specific BiTE antibody in mice. MuS110 was found to have similar in vitro characteristics and in vivo antitumor activity as MT110, a human EpCAM/human CD3-bispecific BiTE antibody that currently is in formal preclinical development. [Cancer Res 2008;68(1):143–51]

There has been little improvement of standard of care for AML patients over the past 20 years, creating a large demand for therapies with improved benefit/risk profile and potential to cure. The CD19/CD3-bispecific, T cell-engaging (BiTE) antibody blinatumomab has shown high response rates and durable remissions in patients with acute lymphocytic leukemia and non-Hodgkin lymphoma. In order to employ this novel therapeutic modality for the treatment of patients with CD19-negative AML, we have constructed a panel of CD33/CD3-bispecific BiTE antibodies and selected MT114 as lead candidate for pre-clinical development for its superior pharmacological and pharmaceutical properties. Its target antigen CD33 (SIGLEC-3) is frequently expressed on AML blasts and leukemic stem cells, and extensive clinical experience has been gained by the CD33-targeting antibodies Mylotarg®, lintuzumab and AVE9633. Here, we report on the biological activities of MT114. MT114 recognized epitopes in the V domain of CD33 and of CD3 epsilon that are conserved between human and macaque antigen, allowing pharmacological and nonclinical safety investigations of the BiTE antibody in macaques as a relevant primate species. MT114-induced redirected lysis of 10 human AML cell lines by unstimulated peripheral blood mononuclear cell (PBMC) at half-maximal concentrations of MT114 between 23 and 328 pg/ml (0.4-7 pM). The 10 AML lines expressed CD33 at 20,000-50,000 molecules/cell. Redirected lysis was specific for CD33-expressing cells, reached completion after 28-h of co-culture, and was effective even at PBMC-to-target ratios of α1:2. MT114 induced the expression of activation markers CD69 and CD25 on T cells and the transient release of IFN-γ, TNF-α and IL-2, -6 and -10 by T cells, but only in the presence of CD33+ target cells. Redirected lysis and T cell activation by MT114 was not affected by up to 100 ng/ml of shed CD33, serum levels of which were found to be associated with AML progression. Neoexpression of CD33 on BiTE-activated T cells did not exceed 8% of total activated T cells when tested with 10 human T cell donors. The BiTE antibody significantly delayed growth of the subcutaneously injected human AML cell line HL60, and induced a robust infiltration of T cells into tumor tissue. MT114 is a highly active novel BiTE antibody with promise for the treatment of AML. 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 3523. doi:1538-7445.AM2012-3523

Treatment with chimeric monoclonal antibody cetuximab has become the standard of care for patients with advanced colorectal cancer (CRC). Cetuximab and other EGFR-specific monoclonal antibodies predominantly inhibit cancer growth by interfering with receptor signalling. Recent analyses have shown that CRC patients with mutated KRAS and BRAF oncogenes do not profit from treatment with such antibodies. Here we have used the binding domains of cetuximab to construct a BiTE antibody that can directly engage and activate T cells by transiently connecting T cells via the CD3 subunit with EGFR-expressing target cells. The cetuximab-based BiTE antibody (C-BiTE) showed potent redirected lysis of KRAS- and BRAF-mutated human CRC lines HCT116 and HT-29, respectively, by unstimulated peripheral human T cells at half maximal concentrations of 10-40 pg/ml (ca. 0.2-0.8 picomolar). The BiTE antibody also completely prevented the outgrowth of tumors from HCT116 and HT-29 xenografts in mice at doses as low as 0.005 mg/kg when given daily i.v. for 10 days. The monoclonal antibody cetuximab was not effective in these models even at 50 mg/kg given twice weekly for 4 weeks. As a prerequisite for nonclinical safety assessment of C-BiTE in non-human primates, crossreactive binding of C-BiTE to CD3 and EGFR antigens of human and Cynomolgus monkey (Macaca fascicularis) origin was demonstrated. This binding translated into a comparable potency of redirected lysis of human EGFR-expressing cancer cells by stimulated Cynomolgus and human PBMC. Continuous i.v. infusion of 6.2 or 12.4 µg/kg C-BiTE to Cynomolgus monkeys for 3 weeks was well tolerated and led to relatively constant serum concentrations of C-BiTE between 1 and 10 ng/ml. In vitro, these serum levels would support a >90% lysis of EGFR-overexpressing CRC cells within 24 h by both Cynomolgus and human effector cells. Of note, no skin toxicity was observed during the 3-week exposure to C-BiTE. The highest doses of 31 and 154 µg/kg caused lethal damage to EGFR-expressing cells in vital organs. Inflammatory cell infiltration into the EGFR-positive tissues was observed at all dose levels but its incidence and severity showed no correlation with clinical signs. Our data suggest that C-BiTE can be safely administered to a relevant non-human primate species at dose levels similar to those of CD19-specific BiTE antibody blinatumumab, which has shown partial and complete responses in lymphoma patients. We anticipate that C-BiTE has a therapeutic window in humans. 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 2429.