Although immune mechanisms can suppress tumour growth, tumours establish potent, overlapping mechanisms that mediate immune evasion. Emerging evidence suggests a link between angiogenesis and the tolerance of tumours to immune mechanisms. Hypoxia, a condition that is known to drive angiogenesis in tumours, results in the release of damage-associated pattern molecules, which can trigger the rejection of tumours by the immune system. Thus, the counter-activation of tolerance mechanisms at the site of tumour hypoxia would be a crucial condition for maintaining the immunological escape of tumours. However, a direct link between tumour hypoxia and tolerance through the recruitment of regulatory cells has not been established. We proposed that tumour hypoxia induces the expression of chemotactic factors that promote tolerance. Here we show that tumour hypoxia promotes the recruitment of regulatory T (T(reg)) cells through induction of expression of the chemokine CC-chemokine ligand 28 (CCL28), which, in turn, promotes tumour tolerance and angiogenesis. Thus, peripheral immune tolerance and angiogenesis programs are closely connected and cooperate to sustain tumour growth.

We describe a novel mechanism regulating the tumor endothelial barrier and T cell homing to tumors. Selective expression of the death mediator Fas ligand (FasL/CD95L) was detected in the vasculature of many human and mouse solid tumors but not in normal vasculature, and in these tumors it was associated with scarce CD8+ infiltration and predominance of FoxP3+ T regulatory (Treg) cells. Tumor-derived vascular endothelial growth factor A (VEGF-A), interleukin 10 (IL-10) and prostaglandin E2 (PGE2) cooperatively induced FasL expression on endothelial cells, which acquired the ability to kill effector CD8+ T cells, but not Treg cells, due to higher levels of cFLIP expression in Tregs. In the mouse, genetic or pharmacologic suppression of FasL produced a significant increase in the influx of tumor-rejecting CD8+ over FoxP3+ T cells. Pharmacologic inhibition of VEGF and PGE2 attenuated tumor endothelial FasL expression, produced a significant increase in the influx of tumor-rejecting CD8+ over FoxP3+ T cells, which was FasL-dependent, and led to CD8-dependent tumor growth suppression. Thus, tumor paracrine mechanisms establish a tumor endothelial death barrier, which plays a critical role in establishing immune tolerance and determining the fate of tumors.

Little is known of the underlying biology of estrogen receptor-negative, progesterone receptor-negative (ER(-)/PR(-)) breast cancer (BC), and few targeted therapies are available. Clinical heterogeneity of ER(-)/PR(-) tumors suggests that molecular subsets exist. We performed genome-wide expression analysis of 99 primary BC samples and eight BC cell lines in an effort to reveal distinct subsets, provide insight into their biology and potentially identify new therapeutic targets. We identified a subset of ER(-)/PR(-) tumors with paradoxical expression of genes known to be either direct targets of ER, responsive to estrogen, or typically expressed in ER(+) BC. Differentially expressed genes included SPDEF, FOXA1, XBP1, CYB5, TFF3, NAT1, APOD, ALCAM and AR (P<0.001). A classification model based on the expression signature of this tumor class identified molecularly similar BCs in an independent human BC data set and among BC cell lines (MDA-MB-453). This cell line demonstrated a proliferative response to androgen in an androgen receptor-dependent and ER-independent manner. In addition, the androgen-induced transcriptional program of MDA-MB-453 significantly overlapped the molecular signature of the unique ER(-)/PR(-) subclass of human tumors. This subset of BCs, characterized by a hormonally regulated transcriptional program and response to androgen, suggests the potential for therapeutic strategies targeting the androgen signaling pathway.

We report the aberrantly strong nuclear immunoreactivity for the C-terminal portion of TFE3 protein in tumors characterized by chromosome translocations involving the TFE3 gene at Xp11.2. This group of tumors includes alveolar soft part sarcoma and a specific subset of renal carcinomas that tend to affect young patients. They contain fusion genes that encode chimeric proteins consisting of the N-terminal portion of different translocation partners fused to the C-terminal portion of TFE3. We postulated that expression of these fusion proteins may be dysregulated in these specific tumors and detectable by immunohistochemistry. We performed immunohistochemistry using a polyclonal antibody to the C-terminal portion of TFE3 in 40 formalin-fixed, paraffin-embedded tumors characterized by TFE3 gene fusions, including 19 alveolar soft part sarcoma (of which nine were molecularly confirmed) and 21 renal carcinomas with cytogenetically confirmed characteristic Xp11.2 translocations and/or fusion transcripts involving TFE3 (11 PRCC-TFE3, 7 ASPL-TFE3, 3 PSF-TFE3). We also screened 1476 other tumors of 64 histologic types from 16 sites for TFE3 immunoreactivity using tissue microarrays and evaluated a broad range of normal tissues. Thirty-nine of 40 neoplasms characterized by TFE3 gene fusions (19 of 19 alveolar soft part sarcoma, 20 of 21 renal carcinomas) demonstrated moderate or strong nuclear TFE3 immunoreactivity. In contrast, only 6 of 1476 other neoplasms labeled for TFE3 (sensitivity 97.5%, specificity 99.6%). Nuclear immunoreactivity in normal tissues was extremely rare. We then applied this assay to a set of 11 pediatric renal carcinomas for which only paraffin-embedded tissue was available, to assess if morphologic features could predict TFE3 immunoreactivity. Of the eight cases in which we suspected that a TFE3 gene rearrangement might be present based on morphology, seven scored positive for nuclear TFE3 labeling. Of the three tumors whose morphology did not suggest the presence of a TFE3 gene fusion, none showed nuclear TFE3 labeling. In summary, we find that nuclear immunoreactivity for TFE3 protein by routine immunohistochemistry is a highly sensitive and specific assay for neoplasms bearing TFE3 gene fusions. Furthermore, the finding in our set of test cases (i.e., that morphologic features can be used to predict TFE3 immunoreactivity) further supports the notion that renal carcinomas with TFE3 gene fusions have a distinctive morphology that corresponds to their genetic distinctiveness. Carcinomas associated with TFE3 gene fusions may account for a significant proportion of pediatric renal carcinomas, and this immunohistochemistry assay may help to clarify their true prevalence.

Summary VHL tumor suppressor loss results in hypoxia inducible factor-alpha (HIF-α) stabilization, and occurs in 70% of sporadic clear cell renal carcinomas (ccRCCs). To determine whether opposing influences of HIF-1α and HIF-2α on c-Myc activity regulate human ccRCC progression, we analyzed VHL genotype and HIF-α expression in 160 primary tumors, which segregated into three groups with distinct molecular characteristics. Interestingly, ccRCCs with intact VHL, as well as pVHL-deficient, HIF-1α/HIF-2α expressing ccRCCs, exhibited enhanced Akt/mTOR and ERK/MAPK signaling. In contrast, pVHL-deficient ccRCCs expressing only HIF-2α displayed elevated c-Myc activity, resulting in enhanced proliferation and resistance to replication stress. These reproducible distinctions in ccRCC behavior delineate HIF-α effects on c-Myc in vivo and suggest molecular criteria for selecting targeted therapies. Significance Constitutive HIF activity is clearly associated with ccRCC tumorigenesis; however, the influence of individual HIF-α subunits on cell growth mechanisms in vivo is unknown. Few dominant oncogenic pathways have been identified within ccRCC, making it difficult to select optimal targeted therapies for patients, or to predict disease outcome, except by grade and stage. Cell culture experiments indicate that HIF-1α inhibits the c-Myc oncoprotein, whereas HIF-2α potentiates c-Myc transcriptional activity and cellular proliferation. The findings reported here indicate that HIF-1α and HIF-2α promote distinct oncogene activation in human ccRCCs, and reveal a critical role for HIF-2α and c-Myc in promoting genomic integrity. These results suggest that evaluating pVHL status and HIF-α expression may aid targeted therapy selection for human ccRCCs.