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Tyro3, Axl, Mer (TAM) receptor tyrosine kinases reduce inflammatory, innate immune responses. We demonstrate that tumor-secreted protein S (Pros1), a Mer/Tyro3 ligand, decreased macrophage M1 cytokine expression in vitro and in vivo. In contrast, tumor cells with CRISPR-based deletion of Pros1 failed to inhibit M1 polarization. Tumor cell-associated Pros1 action was abrogated in macrophages from Mer- and Tyro3- but not Axl-KO mice. In addition, several other murine and human tumor cell lines suppressed macrophage M1 cytokine expression induced by IFN-γ and LPS. Investigation of the suppressive pathway demonstrated a role for PTP1b complexing with Mer. Substantiating the role of PTP1b, M1 cytokine suppression was also lost in macrophages from PTP1b-KO mice. Mice bearing Pros1-deficient tumors showed increased innate and adaptive immune infiltration, as well as increased median survival. TAM activation can also inhibit TLR-mediated M1 polarization. Treatment with resiquimod, a TLR7/8 agonist, did not improve survival in mice bearing Pros1-secreting tumors but doubled survival for Pros1-deleted tumors. The tumor-derived Pros1 immune suppressive system, like PD-L1, was cytokine responsive, with IFN-γ inducing Pros1 transcription and secretion. Inhibition of Pros1/TAM interaction represents a potential novel strategy to block tumor-derived immune suppression.

Purpose Rectal cancer is often clinically resistant to radiotherapy (RT) and identifying molecular markers to define the biologic basis for this phenomenon would be valuable. The nuclear factor κ-light chain-enhancer of activated B cells (NF-κB) is a potential anti-apoptotic transcription factor that has been associated with resistance to RT in model systems. The present study was designed to evaluate NF-κB activation in patients with rectal cancer undergoing chemoradiotherapy to determine whether NF-κB activity correlates with the outcome in rectal cancer patients. Methods and Materials A total of 22 patients underwent biopsy at multiple points in a prospective study and the data from another 50 were analyzed retrospectively. The pretreatment tumor tissue was analyzed for multiple NF-κB subunits by immunohistochemistry. Serial tumor biopsy cores were analyzed for NF-κB–regulated gene expression using reverse transcriptase polymerase chain reaction and for NF-κB subunit nuclear localization using immunohistochemistry. Results Several NF-κB target genes (Bcl-2, cellular inhibitor of apoptosis protein [cIAP]2, interleukin-8, and tumor necrosis factor receptor-associated-1) were significantly upregulated by a single fraction of RT at 24 h, demonstrating for the first time that NF-κB is activated by RT in human rectal tumors. The baseline NF-κB p50 nuclear expression did not correlate with the pathologic response to RT. However, an increasing baseline p50 level was prognostic for overall survival (hazard ratio, 2.15; p = .040). Conclusion NF-κB nuclear expression at baseline in rectal cancer was prognostic for overall survival but not predictive of the response to RT. Larger patient numbers are needed to assess the effect of NF-κB target gene upregulation on the response to RT. Our results suggest that NF-κB might play an important role in tumor metastasis but not to the resistance to chemoradiotherapy.

HER4 expression in human breast cancers correlates with a positive prognosis. While heregulin inhibits the growth of HER4-positive breast cancer cells, it does so by undefined mechanisms. We demonstrate that heregulin-induced HER4 activity inhibits cell proliferation and delays G(2)/M progression of breast cancer cells. While investigating pathways of G(2)/M delay, we noted that heregulin increased the expression of BRCA1 in a HER4-dependent, HER2-independent manner. Induction of BRCA1 by HER4 occurred independently of the cell cycle. Moreover, BRCA1 expression was elevated in HER4-postive human breast cancer specimens. Heregulin stimulated c-Jun N-terminal kinase (JNK), and pharmacologic inhibition of JNK impaired heregulin-enhanced expression of BRCA1 and mitotic delay; inhibition of Erk1/2 did not. Knockdown of BRCA1 with small interfering RNA in a human breast cancer cell line interfered with HER4-mediated mitotic delay. Heregulin/HER4-dependent mitotic delay was examined further with an isogenic pair of mouse mammary epithelial cells (MECs) derived from mice harboring homozygous LoxP sites flanking exon 11 of BRCA1, such that one cell line expressed BRCA1 while the other cell line, after Cre-mediated excision, did not. BRCA1-positive MECs displayed heregulin-dependent mitotic delay; however, the isogenic BRCA1-negative MECs did not. These results suggest that heregulin-mediated growth inhibition in HER4-postive breast cancer cells requires BRCA1.

Yearly, 50,000 Americans die of colorectal cancer metastases to liver and lung. EGFR-targeted agents improve survival in a subset of metastatic colorectal cancer (mCRC) cases, and overexpression of the HER-family ligands amphiregulin (AREG) and epiregulin (EREG) correlates with EGFR-targeted agent susceptibility. Here we present evidence of association between EREG overexpression and disease aggression by showing that knockdown of EREG or HER3 impede anchorage independent growth in the HCT 116 CRC cell line. We also find that a HER3-EREG axis gene signature groups mCRC tumors into prognostically distinct groups. Snap-frozen CRC hepatic metastases (65) with patient matched normal liver, as well as 71 primary CRC tumors with patient matched normal colonic mucosa were analyzed via qRT-PCR for receptors (HER1-4) and ligands (AREG, and EREG). Among the mCRC cases HER2, HER3, AREG, and EREG were expressed at higher levels than unmatched normal mucosa (p50 um diameter) of 170 for HER3, and 285 for EREG as compared to 530 for the empty vector (p 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 4527. doi:1538-7445.AM2012-4527