No abstract

SummaryThe monoclonal antibody G250 (mAbG250) raised against a human renal cell carcinoma (RCC) has been shown to react with a large number of RCCs. Recently, G250 antigen was isolated and found to be homologous to the MN/CA9 gene originally identified in HeLa cells. To determine whether G250 antigen (MN/CA IX/G250) could be a potential therapeutic target and a tumour marker, a total of 147 cases of RCC were investigated immunohistochemically as well as by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. In addition, total RNAs extracted from patients' peripheral blood samples were analysed for MN/CA9/G250 mRNA signals. Immunohistochemistry demonstrated strong expression in 128/147 (87.1%) of RCCs, in contrast to the lack of expression observed in normal tissues. RT-PCR analyses of frozen specimens resulted in the clear detection of MN/CA9/G250 mRNA signals in 137/147 (93.2%), and despite subtle differences the results were almost identical to those for immunohistochemistry. Although high-grade and -stage tumours exhibited significantly lower expression than low-grade and -stage tumours, a large proportion of tumours expressed MN/G250 protein as well as mRNA. RT-PCR analysis of patients' blood samples revealed the presence of circulating MN/CA9/G250 expressing cells. These findings suggest that this antigen may be a potential therapeutic target as well as diagnostic marker for RCCs.

The Wnt signaling pathway is involved in normal embryonic development and controls the homeostatic self-renewal of stem cells in adult tissues. Constitutive activation of Wnt signaling contributes to cancer development and progression. We identified a CXXC4 homozygous deletion at 4q24 in an aggressive renal cell carcinoma (RCC) using single-nucleotide polymorphism (SNP) arrays. CXXC4 encodes Idax, which negatively regulates Wnt signaling by binding to the PDZ domain of Dishevelled. CXXC4 mRNA levels in tumor samples were significantly lower in patients with metastases compared with those without (P ¼ 0.0016). Patients whose tumors had lower CXXC4 expression than normal kidney showed a poorer cause-specific survival outcome than those with higher expression (P ¼ 0.0095). Decreased expression of CXXC4 also correlated with cytoplasmic staining of b-catenin. Knockdown of CXXC4 induced the nuclear translocation of b-catenin and altered expression of a set of genes involved in cell proliferation, invasion and survival. Furthermore, reduced expression of CXXC4 by small interfering RNAs promoted cell proliferation and inhibited apoptosis after 5-FU and doxorubicin treatment in RCC cells. These data suggest that CXXC4 plays a critical role in tumor progression of RCC through Wnt signaling. Wnt signaling could thus be a potential molecular target in RCC indicating decreased CXXC4 expression.

As a physically binding protein of GLI1 transcription factor, Suppressor-of-Fused (SUFU) has been placed in the center of negative regulation of Hedgehog (Hh) signaling. SUFU tethers GLI1 in cytoplasm, and in some circumstances, it moves into the nucleus in association with GLI1, leading to the suppression of GLI1 target gene expression by recruiting a corepressor complex. The activated transcriptional function of GLI1 is important for cellular proliferation in a variety of human cancers. However, it has not been revealed how GLI1 is derepressed from SUFU-mediated suppression. Here, we show SCL/TAL1 interrupting locus (SIL) product, a cytoplasmic protein overexpressed in pancreatic ductal adenocarcinoma (PDA), is responsible for the derepression of GLI1. We found SIL associated with the carboxyl terminus of SUFU, one of two distinct GLI1-binding domains, and this association was responsible for cytoplasmic tethering of SUFU. Overexpressed SIL attenuated SUFU-mediated cytoplasmic tethering and target gene suppression of GLI1. Knockdown of SIL in PDA cells conversely induced the nuclear accumulation of SUFU in association with GLI1 and the transcriptional suppression of GLI1 target genes. Importantly, we also showed that oncogenic K-RAS, and not Sonic hedgehog, enhanced the SIL association with the amino-terminus of SUFU, the other GLI1-binding domain that led to further increase of nuclear translocation of GLI1. These results uncover the role of SIL in derepressing GLI1 from the negative control of SUFU, which is a crucial step for activating Hh signaling in cancer cells. [Cancer Res 2008;68(19):7723-9]

Purpose: A phase I peptide vaccination trial was done in patients with progressive cytokinerefractory metastatic renal cell carcinoma (RCC) to assess both the toxicity and capability to induce immune responses of three peptides (CA9p219-227, p288-296, and p323-331) derived from CA9, a tumor-associated antigen ubiquitously expressed in RCC. Experimental Design: Twenty-three patients positive for human leukocyte antigen (HLA)-A24 with histologically confirmed RCC were enrolled. Eligibility included progressive disease after standard cytokine therapy with interleukin-2 and/or IFN-a. Patients were vaccinated s.c. with the three peptides emulsified in incomplete Freund's adjuvant at 2-week intervals. Pre-and postvaccination blood samples were obtained for toxicity assessment and immunologic studies. Patients were monitored for clinical responses on a 3-monthly basis. Results: Vaccinations were well tolerated without any major adverse event. Most of the patients developed peptide-specific CTLs and/or immunoglobulin G reactive to the peptides after the 6th or 9th vaccination, followed by a gradual increase in both CTL frequency and levels of peptidereactive serum IgG. Three patients with multiple lung metastases showed partial responses with disappearance and shrinking of metastatic lesions. Additionally, stable disease for >6 months was observed in six patients (median duration, 12.2 months). Moreover, the median survival time of all patients who were progressive at trial enrollment after failing immunotherapy was 21.0 months (5-35 months). Conclusions:These results suggest that vaccination of these peptides is safe and recommended for further trials for HLA-A24-positive metastatic RCC patients.