ABSTRACT
Prostate cancer is the second most frequent cancer diagnosed in men worldwide. Localized disease can be successfully treated, but advanced cases are more problematic. After initial effectiveness of androgen deprivation therapy, resistance quickly occurs. Therefore, we aimed to investigate the role of Hedgehog-GLI (HH-GLI) signaling in sustaining androgen-independent growth of prostate cancer cells. We found various modes of HH-GLI signaling activation in prostate cancer cells depending on androgen availability. When androgen was not deprived, we found evidence of non-canonical SMO signaling through the SRC kinase. After short-term androgen deprivation canonical HH-GLI signaling was activated, but we found little evidence of canonical HH-GLI signaling activity in androgen-independent prostate cancer cells. We show that in androgen-independent cells the pathway ligand, SHH-N, non-canonically binds to the androgen receptor through its cholesterol modification. Inhibition of this interaction leads to androgen receptor signaling downregulation. This implies that SHH-N activates the androgen receptor and sustains androgen-independence. Targeting this interaction might prove to be a valuable strategy for advanced prostate cancer treatment. Also, other non-canonical aspects of this signaling pathway should be investigated in more detail and considered when developing potential therapies.
Subject(s)
Androgens/metabolism , Hedgehog Proteins/metabolism , Hedgehog Proteins/physiology , Prostatic Neoplasms/genetics , Prostatic Neoplasms/metabolism , Receptors, Androgen/metabolism , Down-Regulation/genetics , Humans , Male , Molecular Targeted Therapy , Prostatic Neoplasms/pathology , Prostatic Neoplasms/therapy , Signal Transduction/genetics , Signal Transduction/physiology , Tumor Cells, Cultured , Zinc Finger Protein GLI1/metabolism , Zinc Finger Protein GLI1/physiologyABSTRACT
Several signaling pathways are aberrantly activated in head and neck squamous cell carcinoma (HNSCC), including the Hedgehog-Gli (HH-GLI), WNT, EGFR, and NOTCH pathways. The HH-GLI pathway has mostly been investigated in the context of canonical signal transduction and the inhibition of the membrane components of the pathway. In this work we investigated the role of downstream inhibitors GANT61 and lithium chloride (LiCl) on cell viability, wound closure, and colony forming ability of HNSCC cell lines. Five HNSCC cell lines were treated with HH-GLI pathway inhibitors affecting different levels of signal transduction. GANT61 and LiCl reduce the proliferation and colony formation capabilities of HNSCC cell lines, and LiCl has an additional effect on wound closure. The major effector of the HH-GLI signaling pathway in HNSCC is the GLI3 protein, which is expressed in its full-length form and is functionally regulated by GSK3ß. LiCl treatment increases the inhibitory Ser9 phosphorylation of the GSK3ß protein, leading to increased processing of GLI3 from full-length to repressor form, thus inhibiting HH-GLI pathway activity. Therefore, downstream inhibition of HH-GLI signaling may be a promising therapeutic strategy for HNSCC.
Subject(s)
Biomarkers, Tumor/metabolism , Gene Expression Regulation, Neoplastic/drug effects , Glycogen Synthase Kinase 3 beta/metabolism , Head and Neck Neoplasms/drug therapy , Lithium Chloride/pharmacology , Nerve Tissue Proteins/metabolism , Pyridines/pharmacology , Pyrimidines/pharmacology , Zinc Finger Protein Gli3/metabolism , Antimanic Agents/pharmacology , Apoptosis , Biomarkers, Tumor/genetics , Cell Proliferation , Glycogen Synthase Kinase 3 beta/genetics , Head and Neck Neoplasms/metabolism , Head and Neck Neoplasms/pathology , Humans , Nerve Tissue Proteins/antagonists & inhibitors , Nerve Tissue Proteins/genetics , Tumor Cells, Cultured , Zinc Finger Protein Gli3/antagonists & inhibitors , Zinc Finger Protein Gli3/geneticsABSTRACT
Ovarian cancer (OC) is the most lethal female gynecological malignancy, mostly due to diagnosis in late stages when treatment options are limited. Hedgehog-GLI (HH-GLI) signaling is a major developmental pathway involved in organogenesis and stem cell maintenance, and is activated in OC. One of its targets is survivin (BIRC5), an inhibitor of apoptosis protein (IAP) that plays a role in multiple processes, including proliferation and cell survival. We wanted to investigate the role of different GLI proteins in the regulation of survivin isoform expression (WT, 2α, 2B, 3B, and Δex3) in the SKOV-3 OC cell line. We demonstrated that survivin isoforms are downregulated in GLI1 and GLI2 knock-out cell lines, but not in the GLI3 knock-out. Treatment of GLI1 knock-out cells with GANT-61 shows an additional inhibitory effect on several isoforms. Additionally, we examined the expression of survivin isoforms in OC samples and the potential role of BIRC5 polymorphisms in isoform expression. Clinical samples showed the same pattern of survivin isoform expression as in the cell line, and several BIRC5 polymorphisms showed the correlation with isoform expression. Our results showed that survivin isoforms are regulated both by different GLI proteins and BIRC5 polymorphisms in OC.
