Hedgehog signaling pathway is inactive in colorectal cancer cell lines

The Hedgehog (Hh) signaling pathway plays an important role in human development. Abnormal activation of this pathway has been observed in several types of human cancers, such as the upper gastro-intestinal tract cancers. However, activation of the Hh pathway in colorectal cancers is controversial. We analyzed the expression of the main key members of the Hh pathway in 7 colon cancer cell lines in order to discover whether the pathway is constitutively active in these cells. We estimated the expression of SHH, IHH, PTCH, SMO, GLI1, GLI2, GLI3, SUFU and HHIP genes by RT-PCR. Moreover, Hh ligand, Gli3 and Sufu protein levels were quantified by western blotting. None of the cell lines expressed the complete set of Hh pathway members. The ligands were absent from Colo320 and HCT116 cells, Smo from Colo205, HT29 and WiDr. GLI1 gene was not expressed in SW480 cells nor were GLI2/GLI3 in Colo205 or Caco-2 cells. Furthermore the repressive form of Gli3, characteristic of an inactive pathway, was detected in SW480 and Colo320 cells. Finally treatment of colon cancer cells with cyclopamine, a specific inhibitor of the Hh pathway, did not downregulate PTCH and GLI1 genes expression in the colorectal cells, whereas it did so in PANC1 control cells. Taken together, these results indicate that the aberrant activation of the Hh signaling pathway is not common in colorectal cancer cell lines.     

Androgens regulate Hedgehog signalling and proliferation in androgen-dependent prostate cells

Prostate cancer (PCa) is androgen sensitive in its development and progression to metastatic disease. Hedgehog (Hh) pathway activation is important in the initiation and growth of various carcinomas including PCa. We and others have observed aberrations of Hh pathway during the progression of PCa to the castration-resistant state. The involvement of androgen signalling in Hh pathway activation, however, remains largely elusive. Here we investigate the direct role of androgen signalling on Hh pathway. We examined the effect of Dihydrosterone (DHT), antiandrogen, bicalutamide, and Hh pathway inhibitor, KAAD-cyclopamine in four human prostate cell lines (two cancerous: LNCaP, VCaP, and two normal: PNT2 and PNT2-ARm which harbours a mutant version of androgen receptor (AR) that is commonly found in LNCaP). Cell proliferation as well as Hh pathway members (SHH, IHH, DHH, GLI, PTCH) mRNA expression levels were assessed. We showed that KAAD-cyclopamine decreased cell proliferation of DHT-stimulated LNCaP, VCaP and PNT2-ARm cells. SHH expression was found to be downregulated by DHT in all AR posititve cells. The negative effect of DHT on SHH expression was counteracted when cells were treated by bicalutamide. Importantly, KAAD-cyclopamine treatment seemed to inhibit AR activity. Moreover, bicalutamide as well as KAAD-cyclopamine treatments induced GLI and PTCH expression in VCaP and PNT2-ARm. Our results suggest that Hh pathway activity can be regulated by androgen signalling. Specifically, we show that the DHT-induced inhibition of Hh pathway is AR dependent. The mutual interaction between these two pathways might be important in the regulation of cell proliferation in PCa.     

Pharmacological inhibition of the Hedgehog pathway prevents human rhabdomyosarcoma cell growth

The Hedgehog pathway functions as an organizer in embryonic development. Recent studies have shown that mutation of the PTCH1 gene involved in the Hedgehog pathway affects rhabdomyosarcoma development. However, the expression of Hedgehog pathway molecules in human rhabdomyosarcoma cells has not been well clarified. In addition, the effect of pharmacological inhibition of the Hedgehog pathway is not known. We investigated the expression of the genes involved in the Hedgehog pathway using human rhabdomyosarcoma cell lines and biopsy specimens. Further, we evaluated the effect of pharmacological inhibition of the Hedgehog pathway using cyclopamine or GANT61 by WST assay, cell proliferation assay and cell death detection assay. Real-time PCR revealed that human rhabdomyosarcoma cell lines and biopsy specimens overexpressed the following genes: Sonic hedgehog, Indian hedgehog, Desert hedgehog, PTCH1, SMO, GLI1, GLI2 and ULK3. Immunohistochemistry revealed that rhabdomyosarcoma cell lines and biopsy specimens expressed SMO and GLI2. Inhibition of SMO by cyclopamine slowed the growth of human rhabdomyosarcoma cell lines. Similarly, inhibition of GLI by GANT61 slowed the growth of human rhabdomyosarcoma cell lines. Inhibition of cell proliferation and apoptotic cell death together prevented the growth of rhabdomyosarcoma cells by cyclopamine and GANT61 treatment. Our findings suggest that pharmacological inhibition of the Hedgehog pathway may be a useful approach for treating rhabdomyosarcoma patients.     

Targeting Raf/MEK/ERK pathway in pituitary adenomas

Pituitary adenomas are the common neoplasms that cause mass effect and/or endocrine dysfunction. Studies in the pathogenesis and functional regulation of pituitary adenomas are mainly focused on the following two topics: (a) the origin of pituitary adenomas and abnormal physical adjustment due to the activation of oncogenes and loss of function for tumour-suppressor genes; and (b) the mechanistic anomalies of the intracellular signal transduction. Among which, the Raf/MEK/ERK signalling has been considered to be one of the major and central pathways in disease aetiology. Raf/MEK/ERK signalling is evolutionarily conserved that controls cellular growth, differentiation and survival. Altered functionality of this signalling pathway has been found to be involved in the development of several types of cancers in humans including pituitary adenomas. This review summarises the roles of Raf/MEK/ERK signalling pathway in pituitary tumourigenesis and highlights the clinical potential of this signalling pathways to be a therapeutic target for intervention and treatment of pituitary adenomas.