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Supplemental Methods, Figures and Legends

ERK1 and p38 are not activated by alphavbeta6 integrin upon ligand binding.

Full-size scans of PSA immunoblots shown in Figure 5.

Full-size scans of PSA and androgen receptor immunoblots shown in Figure 4.

Increased alphavbeta6 integrin and JNK expression and enhanced JNK nuclear localization in castrated mice.

alphavbeta6 integrin, but not alphavbeta3 integrin, promotes tumor growth.

Androgen receptor signaling fuels prostate cancer and is a major therapeutic target. However, mechanisms of resistance to therapeutic androgen ablation are not well understood. Here, using a prostate cancer mouse model, Ptenpc−/−, carrying a prostate epithelial-specific Pten deletion, we show that the αvβ6 integrin is required for tumor growth in vivo of castrated as well as of noncastrated mice. We describe a novel signaling pathway that couples the αvβ6 integrin cell surface receptor to androgen receptor via activation of JNK1 and causes increased nuclear localization and activity of androgen receptor. This downstream kinase activation by αvβ6 is specific for JNK1, with no involvement of p38 or ERK kinase. In addition, differential phosphorylation of Akt is not observed under these conditions, nor is cell morphology affected by αvβ6 expression. This pathway, which is specific for αvβ6, because it is not regulated by a different αv-containing integrin, αvβ3, promotes upregulation of survivin, which in turn supports anchorage-independent growth of αvβ6-expressing cells. Consistently, both αvβ6 and survivin are significantly increased in prostatic adenocarcinoma, but are not detected in normal prostatic epithelium. Neither XIAP nor Bcl-2 is affected by αvβ6 expression. In conclusion, we show that αvβ6 expression is required for prostate cancer progression, including castrate-resistant prostate cancer; mechanistically, by promoting activation of JNK1, the αvβ6 integrin causes androgen receptor–increased activity in the absence of androgen and consequent upregulation of survivin. These preclinical results pave the way for further clinical development of αvβ6 antagonists for prostate cancer therapy. Cancer Res; 76(17); 5163–74. ©2016 AACR.

alphavbeta6 integrin promotes prostate cancer growth in castrated athymic nu/nu mice.

alphavbeta6 enhances AR transcriptional activity in LNCaP cells.

Supplementary Figure 1 from Cyclooxygenase-2 Inhibition Suppresses αvβ6 Integrin–Dependent Oral Squamous Carcinoma Invasion

Worldwide oral squamous cell carcinoma (OSCC) represents about 5.5% of all malignancies, with ∼30,000 new cases each year in the United States. The integrin αvβ6 and the enzyme cyclooxygenase-2 (COX-2) are implicated in OSCC progression and have been suggested as possible therapeutic targets. Each protein also is reported to identify dysplasias at high risk of malignant transformation, and current clinical trials are testing the efficacy of nonsteroidal anti-inflammatory drugs (NSAID) at preventing OSCC development. Given the probable increased expression of αvβ6 and COX-2 in OSCC and the inhibition of several integrins by NSAIDs, we investigated whether NSAIDs affected αvβ6-dependent cell functions. We found that expression of both αvβ6 and COX-2 was significantly higher in OSCC compared with oral epithelial dysplasias. Neither protein preferentially identified those dysplastic lesions that became malignant. Using OSCC cell lines, modified to express varying levels of αvβ6, we assessed the effect of COX-2 inhibition on cell invasion. We found that the COX-2 inhibitor NS398 inhibited specifically αvβ6-dependent, but not αvβ6-independent, OSCC invasion in vitro and in vivo, and this effect was modulated through prostaglandin E2 (PGE2)–dependent activation of Rac-1. Transient expression of constitutively active Rac-1, or addition of the COX-2 metabolite PGE2, prevented the anti-invasive effect of NS398. Conversely, RNA interference down-regulation of Rac-1 inhibited αvβ6-dependent invasion. These findings suggest that COX-2 and αvβ6 interact in promoting OSCC invasion. This is a novel mechanism that, given the ubiquity of αvβ6 expression by head and neck cancers, raises the possibility that NSAIDs could protect against OSCC invasion. (Cancer Res 2006; 66(22): 10833-42)

Supplementary Figure 2 from Cyclooxygenase-2 Inhibition Suppresses αvβ6 Integrin–Dependent Oral Squamous Carcinoma Invasion

Supplementary Figure Legends from Cyclooxygenase-2 Inhibition Suppresses αvβ6 Integrin–Dependent Oral Squamous Carcinoma Invasion

Androgen receptor signaling fuels prostate cancer and is a major therapeutic target. However, mechanisms of resistance to therapeutic androgen ablation are not well understood. Here, using a prostate cancer mouse model, Ptenpc−/−, carrying a prostate epithelial-specific Pten deletion, we show that the αvβ6 integrin is required for tumor growth in vivo of castrated as well as of noncastrated mice. We describe a novel signaling pathway that couples the αvβ6 integrin cell surface receptor to androgen receptor via activation of JNK1 and causes increased nuclear localization and activity of androgen receptor. This downstream kinase activation by αvβ6 is specific for JNK1, with no involvement of p38 or ERK kinase. In addition, differential phosphorylation of Akt is not observed under these conditions, nor is cell morphology affected by αvβ6 expression. This pathway, which is specific for αvβ6, because it is not regulated by a different αv-containing integrin, αvβ3, promotes upregulation of survivin, which in turn supports anchorage-independent growth of αvβ6-expressing cells. Consistently, both αvβ6 and survivin are significantly increased in prostatic adenocarcinoma, but are not detected in normal prostatic epithelium. Neither XIAP nor Bcl-2 is affected by αvβ6 expression. In conclusion, we show that αvβ6 expression is required for prostate cancer progression, including castrate-resistant prostate cancer; mechanistically, by promoting activation of JNK1, the αvβ6 integrin causes androgen receptor–increased activity in the absence of androgen and consequent upregulation of survivin. These preclinical results pave the way for further clinical development of αvβ6 antagonists for prostate cancer therapy. Cancer Res; 76(17); 5163–74. ©2016 AACR.

The integrin avβ6 promotes migration, invasion and survival of cancer cells, but the biological relevance has yet to be ascertained in breast cancer. Our immunhistochemical analysis of over 2000 breast cancers has revealed that high expression of the protein for the integrin subunit beta6 (β6) is associated with very poor survival (HR = 1.99, P = 2.9×10-6) and increased metastases to distant sites (P = 0·02). This correlation was confirmed at the mRNA level via bioinformatic analysis of the 2000 women in the METABRIC cohort. Furthermore, co-expression of HER2 gave a significantly worse prognosis (HR = 3.43, P = 4×10-12), which we investigated further. We report from in vitro studies that HER2-driven invasion is mediated by αvβ6 in an Akt2-dependent manner. Using the well-tolerated αvβ6-blocking antibody 264RAD in vivo we show that antibody-blockade of this integrin suppressed growth of BT-474 and MCF-7/HER2-18 human breast cancer xenografts similarly to trastuzumab alone (P 264RAD or trastuzumab prolonged survival to a similar degree (14.3% and 33.33% treated mice alive after 100d, respectively, no significant difference) but again, when both drugs were combined 85.7% of mice were alive after 100d, a highly significant response compared with PBS (P Since 70% of women treated with trastuzumab either have, or develop resistance, we suggest combined targeting of αvβ6 and HER2 could provide an important novel therapy for thousands of women with breast cancer. In fact, over 39,000 American women annually (NIH statistics) will develop HER2+ breast cancers for which no specific therapies exist. Our data shows that in excess of 40% of these women with trastuzumab-resistant disease are also likely to express high levels of αvβ6. Our data also suggest that routine determination of the level of expression of αvβ6 on breast cancers would be a valuable clinical tool as it identifies novel high-risk groups of women that require enhanced therapeutic intervention. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-15-01.

The αvβ6 integrin is up-regulated on epithelial malignancies and has been implicated in various aspects of cancer progression. Immunohistochemical analysis of αvβ6 expression in 10 human tumor types showed increased expression relative to normal tissues. Squamous carcinomas of the cervix, skin, esophagus, and head and neck exhibited the highest frequency of expression, with positive immunostaining in 92% (n = 46), 84% (n = 49), 68% (n = 56), and 64% (n = 100) of cases, respectively. We studied the role of αvβ6 in Detroit 562 human pharyngeal carcinoma cells in vitro and in vivo. Prominent αvβ6 expression was detected on tumor xenografts at the tumor-stroma interface resembling the expression on human head and neck carcinomas. Nonetheless, coculturing cells in vitro with matrix proteins did not up-regulate αvβ6 expression. Detroit 562 cells showed αvβ6-dependent adhesion and activation of transforming growth factor-β (TGF-β) that was inhibited >90% with an αvβ6 blocking antibody, 6.3G9. Although both recombinant soluble TGF-β receptor type-II (rsTGF-βRII-Fc) and 6.3G9 inhibited TGF-β–mediated Smad2/3 phosphorylation in vitro, there was no effect on proliferation. Conversely, in vivo, 6.3G9 and rsTGF-βRII-Fc inhibited xenograft tumor growth by 50% (n = 10, P < 0.05) and >90% (n = 10, P < 0.001), respectively, suggesting a role for the microenvironment in this response. However, stromal collagen and smooth muscle actin content in xenograft sections were unchanged with treatments. Although further studies are required to consolidate in vitro and in vivo results and define the mechanisms of tumor inhibition by αvβ6 antibodies, our findings support a role for αvβ6 in human cancer and underscore the therapeutic potential of function blocking αvβ6 antibodies. [Cancer Res 2008;68(2):561–70]

Enhanced expression levels of integrin αvβ6 have been linked to more aggressive invasive carcinoma cell behavior and poorer clinical prognosis. However, how αvβ6 determines invasion and the dynamics of integrin αvβ6 regulation in tumor cells are poorly understood. We have identified the 35-kDa HS1-associated protein X-1 (HAX-1) protein as a novel binding partner of the β6 cytoplasmic tail using a yeast two-hybrid screen. We show that αvβ6-dependent migration is blocked following small interfering RNA (siRNA)–mediated depletion of HAX-1 in oral squamous cell carcinoma cell lines. Using both siRNA and membrane-permeable peptides, we show that αvβ6-dependent migration and invasion require HAX-1 to bind directly to β6 and thereby regulate clathrin-mediated endocytosis of αvβ6 integrins. Progression of oral cancer is associated with enhanced expression of αvβ6 and HAX-1 proteins in patient tissue. This report establishes that integrin endocytosis is required for αvβ6-dependent carcinoma cell motility and invasion and suggests that this process is an important mechanism in cancer progression. [Cancer Res 2007;67(11):5275–84]

Worldwide oral squamous cell carcinoma (OSCC) represents about 5.5% of all malignancies, with approximately 30,000 new cases each year in the United States. The integrin alpha(v)beta(6) and the enzyme cyclooxygenase-2 (COX-2) are implicated in OSCC progression and have been suggested as possible therapeutic targets. Each protein also is reported to identify dysplasias at high risk of malignant transformation, and current clinical trials are testing the efficacy of nonsteroidal anti-inflammatory drugs (NSAID) at preventing OSCC development. Given the probable increased expression of alpha(v)beta(6) and COX-2 in OSCC and the inhibition of several integrins by NSAIDs, we investigated whether NSAIDs affected alpha(v)beta(6)-dependent cell functions. We found that expression of both alpha(v)beta(6) and COX-2 was significantly higher in OSCC compared with oral epithelial dysplasias. Neither protein preferentially identified those dysplastic lesions that became malignant. Using OSCC cell lines, modified to express varying levels of alpha(v)beta(6), we assessed the effect of COX-2 inhibition on cell invasion. We found that the COX-2 inhibitor NS398 inhibited specifically alpha(v)beta(6)-dependent, but not alpha(v)beta(6)-independent, OSCC invasion in vitro and in vivo, and this effect was modulated through prostaglandin E(2) (PGE(2))-dependent activation of Rac-1. Transient expression of constitutively active Rac-1, or addition of the COX-2 metabolite PGE(2), prevented the anti-invasive effect of NS398. Conversely, RNA interference down-regulation of Rac-1 inhibited alpha(v)beta(6)-dependent invasion. These findings suggest that COX-2 and alpha(v)beta(6) interact in promoting OSCC invasion. This is a novel mechanism that, given the ubiquity of alpha(v)beta(6) expression by head and neck cancers, raises the possibility that NSAIDs could protect against OSCC invasion.

Background: Integrin αvβ6 promotes migration, invasion and survival of cancer cells, however, the relevance and role of αvβ6 has yet to be elucidated in breast cancer. Methods: Protein expression of integrin subunit beta6 (β6) was measured in over 2000 breast cancers by immunohistochemistry and ITGB6 mRNA expression measured in the METABRIC dataset. Overall survival was assessed using Kaplan-Meier curves and bioinformatics statistical analyses were performed in R statistical environment v2.14.1. Using antibody (264RAD; supplied by AZ-Medimmune) blockade and siRNA knockdown of β6 in breast cell lines, the role of αvβ6 in HER2 biology (expression, proliferation, invasion, growth in vivo) was assessed by flow cytometry, MTT assays and Transwell invasion assays and xenografts, respectively. All statistical tests were two-sided. Results: High expression of either the mRNA or protein for the integrin subunit β6 correlated with very poor survival (HR=1.99, P=2.9x10-6) and increased metastases to distant sites (P=0.02). Co-expression of β6 and HER2 gave a worse prognosis (HR=3.43, P=4x10-12). HER2-driven invasion was mediated by αvβ6 in an Akt2-dependent manner. Monotherapy with 264RAD or trastuzumab, slowed growth of MCF-7/HER2-18 and BT-474 xenografts to a similar degree (P Conclusions: Targeting αvβ6 with 264RAD alone or in combination with trastuzumab may provide a novel therapy for treating high-risk and trastuzumab-resistant breast cancer patients, giving hope to the 70% of women treated who have, or develop, resistance. Moreover, routine determination of the level of expression of αvβ6 on breast cancers would stratify women into higher-risk categories, requiring enhanced therapeutic intervention. Citation Format: Kate M. Moore, Gareth J. Thomas, Stephen W. Duffy, Jane Warwick, Rhian Gabe, Patrick Chou, Ian O. Ellis, Andrew R. Green, Syed Haider, Kellie Brouilette, Antonio Saha, Sabari Vallath, Rebecca Bowen, Claudia Chelala, Diana Eccles, William J. Tapper, Alastair M. Thompson, Phillip Quinlan, Lee Jordan, Cheryl Gillett, Adam Brentnall, Sheila Violette, Paul Weinreb, Jane Kendrew, Simon T. Barry, Ian R. Hart, Louise Jones, John F. Marshall. Therapeutic targeting of integrin αvβ6 in high-risk breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B046.