The Birt–Hogg–Dubé (BHD) disease is a genetic cancer syndrome. The responsible gene, BHD, has been identified by positional cloning and thought to be a novel tumor suppressor gene. BHD mutations cause many types of diseases including renal cell carcinomas, fibrofolliculomas, spontaneous pneumothorax, lung cysts, and colonic polyps/cancers. By combining Gateway Technology with the Ksp-Cre gene knockout system, we have developed a kidney-specific BHD knockout mouse model. BHDflox/flox/Ksp-Cre mice developed enlarged kidneys characterized by polycystic kidneys, hyperplasia, and cystic renal cell carcinoma. The affected BHDflox/flox/Ksp-Cre mice died of renal failure at approximate three weeks of age, having blood urea nitrogen levels over tenfold higher than those of BHD flox/+/Ksp-Cre and wild-type littermate controls. We further demonstrated that these phenotypes were caused by inactivation of BHD and subsequent activation of the mTOR pathway. Application of rapamycin, which inhibits mTOR activity, to the affected mice led to extended survival and inhibited further progression of cystogenesis. These results provide a correlation of kidney-targeted gene inactivation with renal carcinoma, and they suggest that the BHD product FLCN, functioning as a cyst and tumor suppressor, like other hamartoma syndrome–related proteins such as PTEN, LKB1, and TSC1/2, is a component of the mTOR pathway, constituting a novel FLCN-mTOR signaling branch that regulates cell growth/proliferation.

Alterations in Wnt/␤-catenin signaling have been linked to abnormal kidney development and tumorigenesis. To gain more insights into the effects of these alterations, we created mice carrying a conditional deletion of the Apc tumor suppressor gene specifically in the renal epithelium. As expected, the loss of Apc leads to increased levels of ␤-catenin protein in renal epithelium. Most of these mice die shortly after birth, and multiple kidney cysts were found upon histological examination. Only rarely did these animals survive to adulthood. Analysis of these adults revealed severely cystic kidneys associated with the presence of renal adenomas. Our results confirm an important role for proper regulation of Wnt/␤-catenin signaling in renal development and provide evidence that dysregulation of the pathway can initiate tumorigenesis in the kidney.

Background. Oncogenic genetic alterations "drive" neoplastic cell proliferation. Small molecule inhibitors and antibodies are being developed that target an increasing number of these altered gene products. Next-generation sequencing (NGS) is a powerful tool to identify tumor-specific genetic changes. To determine the clinical impact of extensive genetic analysis, we reviewed our experience using a targeted NGS platform (FoundationOne) in advanced cancer patients. Patients and Methods. We retrospectively assessed demographics, NGS results, and therapies received for patients undergoing targeted NGS (exonic sequencing of 236 genes and selective intronic sequencing from 19 genes) between April 2012 and August 2013. Coprimary endpoints were the percentage of patients with targeted therapy options uncovered by mutational profiling and the percentage who received genotype-directed therapy.

Urothelial carcinoma of the renal pelvis is a deadly disease with an unclear tumorigenic mechanism. We conducted gene expression profiling on a set of human tumors of this type and identified a phosphatidylinositol 3-kinase (PI3K)/AKT activation expression signature in 76.9% (n = 13) of our samples. Sequence analysis found both activating mutations of PIK3CA (13.6%, n = 22) and loss of heterozygosity at the PTEN locus (25%, n = 8). In contrast, none of the other subtypes of kidney neoplasms (e.g., clear-cell renal cell carcinoma) harbored PIK3CA mutations (n = 87; P < 0.001). Immunohistochemical analysis of urothelial carcinoma samples found loss of PTEN protein expression (36.4%, n = 11) and elevation of phosphorylated mammalian target of rapamycin (mTOR; 63.6%, n = 11). To confirm the role of the PI3K/AKT pathway in urothelial carcinoma, we generated mice containing biallelic inactivation of Pten in the urogenital epithelia. These mice developed typical renal pelvic urothelial carcinomas, with an incidence of 57.1% in mice older than 1 year. Laser capture microdissection followed by PCR confirmed the deletion of Pten exons 4 and 5 in the animal tumor cells. Immunohistochemical analyses showed increased phospho-mTOR and phospho-S6K levels in the animal tumors. Renal lymph node metastases were found in 15.8% of the animals with urothelial carcinoma. In conclusion, we identified and confirmed an important role for the PI3K/AKT pathway in the development of urothelial carcinoma and suggested that inhibitors of this pathway (e.g., mTOR inhibitor) may serve as effective therapeutic agents.