The primary cilium is a well-established target in the pathogenesis of numerous developmental and chronic disorders, and more recently is attracting interest as a structure relevant to cancer. Here we discuss mechanisms by which changes in cilia can contribute to the formation and growth of tumors. We emphasize the cancer-relevance of cilia-dependent signaling pathways and proteins including mTOR, VHL, TSC, WNT, Aurora-A, NEDD9, and Hedgehog, and highlight the emerging role of ciliary dysfunction in renal cell carcinoma, medulloblastoma, and breast cancer.

Significance This study uses mouse models for the first time to our knowledge to identify that NEDD9, a nonenzymatic scaffolding protein that is commonly amplified in cancer, has an important restraining function for the development of renal cysts in autosomal dominant polycystic kidney disease (ADPKD). In the absence of NEDD9, failure to activate Aurora-A kinase causes multiple abnormalities in cilia, intensifying the effect of genetic deficiency of mutations in the polycystic kidney disease (PKD) 1 gene, the most common cause of PKD. As important implications, clinical inhibitors of Aurora-A also intensified ADPKD induced by mutation of PKD1 , suggesting caution in use of these agents, whereas recently reported polymorphisms in Nedd9 may contribute to the genetic heterogeneity of ADPKD presentation in affected families.

Overexpression of the NEDD9/HEF1/Cas-L scaffolding protein is frequent, and drives invasion and metastasis in breast, head and neck, colorectal, melanoma, lung, and other types of cancer. We have examined the consequences of genetic ablation of Nedd9 in the MMTV-HER2/ERBB2/neu mouse mammary tumor model. Unexpectedly, we found that only a limited effect on metastasis in MMTV-neu;Nedd9−/− mice compared to MMTV-neu;Nedd9+/+ mice, but instead a dramatic reduction in tumor incidence (18% versus 80%), and a significantly increased latency until tumor appearance. Orthotopic reinjection and tail vein injection of cells arising from tumors, coupled with in vivo analysis, indicated tumors arising in MMTV-neu;Nedd9−/− mice had undergone mutational selection that overcame the initial requirement for Nedd9. To better understand the defects in early tumor growth, we compared mammary progenitor cell pools from MMTV-neu;Nedd9−/− versus MMTV-neu;Nedd9+/+ mice. The MMTV-neu;Nedd9−/− genotype selectively reduced both the number and colony-forming potential of mammary luminal epithelial progenitor cells, while not affecting basal epithelial progenitors. MMTV-neu;Nedd9−/−mammospheres had striking defects in morphology and cell polarity. All of these defects were seen predominantly in the context of the HER2/neu oncogene, and were not associated with randomization of the plane of mitotic division, but rather with depressed expression the cell attachment protein FAK, accompanied by increased sensitivity to small molecule inhibitors of FAK and SRC. Surprisingly, in spite of these significant differences, only minimal changes were observed in the gene expression profile of Nedd9−/− mice, indicating critical Nedd9-dependent differences in cell growth properties were mediated via post-transcriptional regulation of cell signaling. Coupled with emerging data indicating a role for NEDD9 in progenitor cell populations during the morphogenesis of other tissues, these results indicate a functional requirement for NEDD9 in the growth of mammary cancer progenitor cells.

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Background: Cystinosis is an autosomal recessive lysosomal storage disorder characterized by accumulation of cystine in lysosomes throughout the body. Cystinosis is caused by mutations in the CTNS gene that encodes the lysosomal cystine carrier protein cystinosin. CTNS mutations result in either complete absence or reduced cystine transporting function of the protein. The diagnosis of nephropathic cystinosis is generally based on measuring leukocyte cystine level, demonstration of corneal cystine crystals by the slit lamp examination and confirmed by genetic analysis of the CTNS gene. Case presentation: A boy born to consanguineous Caucasian parents had the characteristic clinical features of the infantile nephropathic cystinosis including renal Fanconi syndrome (polydipsia/polyuria, metabolic acidosis, hypokalemia, hypophosphatemia, low molecular weight proteinuria, glycosuria, cystine crystals in the cornea) and elevated WBC cystine levels. Initially we performed RFLP analysis of the common in the Northern European population 57-kb deletion of proband's DNA, then a direct Sanger sequencing which revealed no mutations in the coding part of the CTNS gene. To confirm the diagnosis we performed RT-PCR analysis of total RNA obtained from patient-derived fibroblasts in combination with cDNA sequencing. This revealed the skipping of exon 4 and exon 5 in the CTNS in our patient. Therefore, we detected a novel 9-kb homozygous deletion in the CTNS gene at genomic DNA level, spanning region from intron 3 to intron 5. In order to identify the inheritance pattern of the deletion we analyzed DNA of proband's mother and father. Both parents were found to be heterozygous carriers of the CTNS mutation. Conclusions: Analysis of CTNS gene transcript allowed to identify a large homozygous deletion in the patient with infantile nephropathic cystinosis. Mutational detection at RNA level may be an efficient tool to establish the genetic defect in some cystinosis patients.