The sonic hedgehog signaling pathway is reactivated in human renal cell carcinoma and plays orchestral role in tumor growth.
BACKGROUND
Human clear cell renal cell carcinoma (CRCC) remains resistant to therapies. Recent advances in Hypoxia Inducible Factors (HIF) molecular network led to targeted therapies, but unfortunately with only limited clinical significance. Elucidating the molecular processes involved in kidney tumorigenesis and resistance is central to the development of improved therapies, not only for kidney cancer but for many, if not all, cancer types. The oncogenic PI3K/Akt, NF-kB and MAPK pathways are critical for tumorigenesis. The sonic hedgehog (SHH) signaling pathway is crucial to normal development.


RESULTS
By quantitative RT-PCR and immunoblot, we report that the SHH signaling pathway is constitutively reactivated in tumors independently of the von Hippel-Lindau (VHL) tumor suppressor gene expression which is inactivated in the majority of CRCC. The inhibition of the SHH signaling pathway by the specific inhibitor cyclopamine abolished CRCC cell growth as assessed by cell counting, BrdU incorporation studies, fluorescence-activated cell sorting and beta-galactosidase staining. Importantly, inhibition of the SHH pathway induced tumor regression in nude mice through inhibition of cell proliferation and neo-vascularization, and induction of apoptosis but not senescence assessed by in vivo studies, immunoblot and immunohistochemistry. Gli1, cyclin D1, Pax2, Lim1, VEGF, and TGF-beta were exclusively expressed in tumors and were shown to be regulated by SHH, as evidenced by immunoblot after SHH inhibition. Using specific inhibitors and immunoblot, the activation of the oncogenic PI3K/Akt, NF-kB and MAPK pathways was decreased by SHH inhibition.


CONCLUSIONS
These findings support targeting SHH for the treatment of CRCC and pave the way for innovative and additional investigations in a broad range of cancers.
Dormoy
Valérian
V
INSERM U682, Section of Renal Cancer and Renal Physiopathology, University of Strasbourg, School of Medicine, Strasbourg, 67085 France. valerian.dormoy@medecine.u-strasbg.fr
Danilin
Sabrina
S
Lindner
Véronique
V
Thomas
Lionel
L
Rothhut
Sylvie
S
Coquard
Catherine
C
Helwig
Jean-Jacques
JJ
Jacqmin
Didier
D
Lang
Hervé
H
Massfelder
Thierry
T
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014704:Veratrum Alkaloids / Q000494:pharmacology; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
D053823:Hedgehog Proteins; C509239:SHH protein, human; D014704:Veratrum Alkaloids; D051794:Von Hippel-Lindau Tumor Suppressor Protein; C497446:VHL protein, human; C000541:cyclopamine