The lymphotoxin-B receptor (LTBR) is a tumor necrosis factor receptor family member critical for the development and maintenance of various lymphoid microenvironments. Herein, we show that agonistic anti-LTBR monoclonal antibody (mAb) CBE11 inhibited tumor growth in xenograft models and potentiated tumor responses to chemotherapeutic agents. In a syngeneic colon carcinoma tumor model, treatment of the tumor-bearing mice with an agonistic antibody against murine LTBR caused increased lymphocyte infiltration and necrosis of the tumor. A pattern of differential gene expression predictive of cellular and xenograft response to LTBR activation was identified in a panel of colon carcinoma cell lines and when applied to a panel of clinical colorectal tumor samples indicated 35% likelihood a tumor response to CBE11. Consistent with this estimate, CBE11 decreased tumor size and/or improved long-term animal survival with two of six independent orthotopic xenografts prepared from surgical colorectal carcinoma samples. Targeting of LTBR with agonistic mAbs offers a novel approach to the treatment of colorectal and potentially other types of cancers.

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Integrin ␣ 4 ␤ 1 plays an important role in inflammatory processes by regulating the migration of lymphocytes into inflamed tissues. Here we evaluated the biochemical, pharmacological, and pharmacodynamic properties and efficacy in experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis, of two types of ␣ 4 ␤ 1 inhibitors, the anti-rat ␣ 4 monoclonal antibody TA-2 and the small molecule inhibitor. TA-2 has been extensively studied in rats and provides a benchmark for assessing function. BIO5192 is a highly selective and potent (K D of Ͻ10 pM) inhibitor of ␣ 4 ␤ 1 . Dosing regimens were identified for both inhibitors, which provided full receptor occupancy during the duration of the study.Both inhibitors induced leukocytosis, an effect that was used as a pharmacodynamic marker of activity, and both were efficacious in the EAE model. Treatment with TA-2 caused a decrease in ␣ 4 integrin expression on the cell surface, which resulted from internalization of ␣ 4 integrin/TA-2 complexes. In contrast, BIO5192 did not modulate cell surface ␣ 4 ␤ 1 . Our results with BIO5192 indicate that ␣ 4 ␤ 7 does not play a role in this model and that blockade of ␣ 4 ␤ 1 /ligand interactions without down-modulation is sufficient for efficacy in rat EAE. BIO5192 is highly selective and binds with high affinity to ␣ 4 ␤ 1 from four of four species tested. These studies demonstrate that BIO5192, a novel, potent, and selective inhibitor of ␣ 4 ␤ 1 integrin, will be a valuable reagent for assessing ␣ 4 ␤ 1 biology and may provide a new therapeutic for treatment of human inflammatory diseases.Integrins are a large family of cell surface receptors that mediate cell/cell and cell/matrix interactions and signal transduction. They exist as noncovalent ␣␤ heterodimers of different combinations of ␣ and ␤ chains and share extensive structural homology. The leukocyte integrin ␣ 4 ␤ 1 regulates normal lymphocyte trafficking (Lobb and Hemler, 1994) and provides a key costimulatory signal supporting cell activation (Clark and Brugge, 1995). During inflammatory responses, it regulates lymphocyte migration into the damaged tissues and thus has been recognized as an attractive therapeutic target. In vivo studies using blocking monoclonal antibodies (Lobb and Hemler, 1994) and inhibitory peptides (Molossi et al., 1995) have verified the critical role of ␣ 4 ␤ 1 integrins in leukocyte-mediated inflammation. Numerous EAE models of multiple sclerosis have been designed to recapitulate important aspects of the disease and are responsive to ␣ 4 inhibitors (Yednock et al., 1992). Recent positive phase II data using the anti-␣ 4 antibody 1 Current address: Wyeth, Cambridge, MA.

Despite progress in identifying molecular drivers of cancer, it has been difficult to translate this knowledge into new therapies, because many of the causal proteins cannot be inhibited by conventional small molecule therapeutics. RNA interference (RNAi), which uses small RNAs to inhibit gene expression, provides a promising alternative to reach traditionally undruggable protein targets by shutting off their expression at the messenger RNA (mRNA) level. Challenges for realizing the potential of RNAi have included identifying the appropriate genes to target and achieving sufficient knockdown in tumors. We have developed high-potency Dicer-substrate short-interfering RNAs (DsiRNAs) targeting β-catenin and delivered these in vivo using lipid nanoparticles, resulting in significant reduction of β-catenin expression in liver cancer models. Reduction of β-catenin strongly reduced tumor burden, alone or in combination with sorafenib and as effectively as DsiRNAs that target mitotic genes such as PLK1 and KIF11. β-catenin knockdown also strongly reduced the expression of β-catenin–regulated genes, including MYC, providing a potential mechanism for tumor inhibition. These results validate β-catenin as a target for liver cancer therapy and demonstrate the promise of RNAi in general and DsiRNAs in particular for reaching traditionally undruggable cancer targets.

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