MMP activity appears to play an important role in bone matrix turnover when prostate cancer cells are present in bone. Bone matrix turnover and metastatic tumor growth appear to be involved in a mutually supportive cycle that is disrupted by MMP inhibition.

Integrins of the ␣v family, such as ␣v␤3 and ␣v␤5, are implicated in tumor-induced angiogenesis; but their role in tumor growth has not been fully explored. CNTO 95 is a fully human antibody that recognizes the ␣v family of integrins and is likely to be less immunogenic in humans compared to chimeric or humanized antibodies. CNTO 95 bound to purified ␣v␤3 and ␣v␤5 with a

Members of the signal transducer and activator of transcription (STAT) family of transcription factors are potential targets for the treatment and prevention of cancers including non-small-cell lung cancer. STAT proteins can be phosphorylated and activated by diverse upstream kinases including cytokine receptors and tyrosine kinases. We examined STAT protein activation in lung cancer cell lines including those with activating mutations in the EGFR and examined upstream kinases responsible for STAT3 phosphorylation and activation using small molecules, antibodies, and RNA interference. We found more pronounced STAT3 activation in cells with activating EGFR mutations, yet inhibition of EGFR activity had no effect on STAT3 activation. Inhibition of JAK1 with small molecules or RNA interference resulted in loss of STAT3 tyrosine phosphorylation and inhibition of cell growth. An interleukin-6 neutralizing antibody, siltuximab (CNTO 328) could inhibit STAT3 tyrosine phosphorylation in a cell-dependent manner. Siltuximab could completely inhibit STAT3 tyrosine phosphorylation in H1650 cells, and this resulted in inhibition of lung cancer cell growth in vivo. Combined EGFR inhibition with erlotinib and siltuximab resulted in dual inhibition of both tyrosine and serine STAT3 phosphorylation, more pronounced inhibition of STAT3 transcriptional activity, and translated into combined effects on lung cancer growth in a mouse model. Our results suggest that JAK1 is responsible for STAT3 activation in lung cancer cells and that indirect attacks on JAK1-STAT3 using an IL-6 neutralizing antibody with or without EGFR inhibition can inhibit lung cancer growth in lung cancer subsets.

Integrins are heterodimeric cell adhesion receptors that mediate intercellular communication through cell-extracellular matrix interactions and cell-cell interactions. Integrins have been demonstrated to play a direct role in cancer progression, specifically in tumor cell survival, tumor angiogenesis, and metastasis. Therefore, agents targeted against integrin function have potential as effective anticancer therapies. Numerous anti-integrin agents, including monoclonal antibodies and small-molecule inhibitors, are in clinical development for the treatment of solid and hematologic tumors. This review focuses on the role of alpha(v) integrins in cancer progression, the current status of integrin-targeted agents in development, and strategies for the clinical development of anti-integrin therapies.

Tumor-associated macrophages (TAMs) have been shown to promote tumor progression, and increased TAM infiltration often correlates with poor prognosis. However, questions remain regarding the phenotype of macrophages within the tumor and their role in mAb-dependent cytotoxicity. This study demonstrates that whereas TAMs have protumor properties, they maintain Fc-dependent anti-tumor function. CD11b+CD14+ TAMs isolated from primary human breast tumors expressed activating FcγRs. To model breast cancer TAMs in vitro, conditioned medium from breast cancer cells was used to drive human peripheral monocyte differentiation into macrophages. Tumor-conditioned macrophages were compared with in vitro derived M1 and M2a macrophages and were found to promote tumor cell invasion and express M2a markers, confirming their protumor potential. However, unlike M2a macrophages, tumor-conditioned macrophages expressed FcγRs and phagocytosed tumor cells in the presence of a tumor Ag-targeting mAb, unmasking an underappreciated tumoricidal capacity of TAMs. In vivo macrophage depletion reduced the efficacy of anti-CD142 against MDA-MB-231 xenograft growth and metastasis in SCID/beige mice, implicating a critical role for macrophages in Fc-dependent cell killing. M-CSF was identified in tumor-conditioned media and shown to be capable of differentiating macrophages with both pro- and anti-tumor properties. These results highlight the plasticity of TAMs, which are capable of promoting tumor progression and invasion while still retaining tumoricidal function in the presence of tumor-targeting mAbs.

Initially, prostate cancer is androgen dependent. However, most cases progress to an androgen-independent state through unknown mechanisms. Interleukin-6 (IL-6) has been associated with prostate cancer progression including activation of the androgen receptor (AR). To determine if IL-6 plays a role in the conversion of prostate cancer from androgen dependent to androgen independent, we established androgen-dependent LuCaP 35 human prostate cancer xenografts in nude mice, castrated the mice, and blocked IL-6 activity using a neutralizing antibody (CNT0328) for a period of 18 weeks. IL-6 inhibition increased survival of mice and inhibited tumor growth, as reflected by decreased tumor volume and prostatespecific antigen levels, compared with that in mice receiving isotype control antibody. To test the effect of IL-6 inhibition on the conversion from androgen dependent to androgen independent, tumor cells from the treated mice were assessed for their androgen dependence both in vitro and by implanting them into sham-operated or orchiectomized mice. Tumor cells derived from the isotype-treated animals converted to androgen-independent state, whereas tumor cells from the anti-IL-6 antibody-treated mice were still androgen dependent in vitro and in vivo. Although there was no difference in AR levels between the androgen-independent and androgen-dependent tumors, IL-6 inhibition promoted both apoptosis and inhibited cell proliferation in tumors and blocked the orchiectomyinduced expression of histone acetylases, p300 and CBP, which are AR cofactors. These data show that IL-6 contributes to the development of androgen independence in prostate cancer and suggest that it mediates this effect, in part, through modulation of p300 and CBP. (Cancer Res 2006; 66(6): 3087-95)

Suppressor of cytokine signaling-3 (SOCS-3) acts as a negative feedback regulator of the Janus-activated kinase/ signal transducers and activators of transcription factors signaling pathway and plays an important role in the development and progression of various cancers. To better understand the role of SOCS-3 in prostate cancer, SOCS-3 expression was down-regulated in DU-145, LNCaP-IL-6+, and PC3 cells by consecutive SOCS-3 small interfering RNA transfections. SOCS-3 mRNA and protein expression as measured by quantitative reverse transcription-PCR and Western blot, respectively, were decreased by f70% to 80% compared with controls. We observed a significant decrease in cell proliferation and viability in all SOCS-3-positive cell lines but not in the parental LNCaP cell line, which is SOCS-3 negative. In this study, we show that down-regulation of SOCS-3 leads to an increased cell death in prostate cancer cell lines. We found a considerable increase in the activation of the proapoptotic caspase-3/caspase-7, caspase-8, and caspase-9. A significant up-regulation of cleaved poly(ADPribose) polymerase and inhibition of Bcl-2 expression was observed in all SOCS-3-positive cell lines. Overexpression of Bcl-2 could rescue cells with decreased SOCS-3 levels from going into apoptosis. Tissue microarray data prove that SOCS-3 is highly expressed in castration-refractory tumor samples. In conclusion, we show that SOCS-3 is an important protein in the survival machinery in prostate cancer and is overexpressed in castration-resistant tumors. SOCS-3 knockdown results in an increase of cell death via activation of the extrinsic and intrinsic apoptosis pathways.

in association with the Biotherapy Development Association Abstract Purpose: A fully human monoclonal antibody to anti^a v integrins (CNTO 95) has been shown to inhibit angiogenesis and tumor growth in preclinical studies. We assessed the safety and pharmacokinetics of CNTO 95 in patients with advanced refractory solid tumors. Experimental Design: In this phase I trial, CNTO 95 (0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg) was infused on days 0, 28, 35, and 42, and clinical assessments, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and [18 F]-2-fluorodeoxyglucose positron emission tomography (FDG-PET) were done. Patients achieving stable disease or better were eligible for extended dosing every 3 weeks for up to 12 months. Results: Among the 24 enrolled patients, CNTO 95 was associated with one episode of grade III and four episodes of grade II infusion-related fever (all responded to acetaminophen). Of the six patients who received extended dosing, one patient (10.0 mg/kg), with cutaneous angiosarcoma, had a 9-month partial response. Pre-and post-treatment lesion biopsies confirmed tumor cell a v integrin expression, as well as CNTO 95 penetration of the tumor and localization to tumor cells in association with reduced bcl-2 expression. A lesion in one patient (10.0 mg/kg) with stable ovarian carcinosarcoma was no longer detectable by FDG-PET by day 49. Exposure to CNTO 95 seemed to increase in a greater-than-dose-proportional manner; dose-dependent mean halflife ranged from 0.26 to 6.7 days. Conclusions: CNTO 95 was generally well tolerated. Six patients received extended therapy, including one patient with a prolonged response. Biopsy data confirmed tumor localization and pharmacodynamic activity.