Sonic hedgehog signalling proteins are frequently expressed in retinoblastoma and are associated with aggressive clinicopathological features

Therapeutic potential of hedgehog signaling in advanced cancer types

In this chapter, we have made an attempt to elucidate the relevance of hedgehog signaling pathway in tumorigenesis. Here, we have described different types of hedgehog signaling (canonical and non-canonical) with emphasis on the different mechanisms (mutation-driven, autocrine, paracrine and reverse paracrine) it adopts during tumorigenesis. We have discussed the role of hedgehog signaling in regulating cell proliferation, invasion and epithelial-to-mesenchymal transition in both local and advanced cancer types, as reported in different studies based on preclinical and clinical models. We have specifically addressed the role of hedgehog signaling in aggressive neuroendocrine tumors as well. We have also elaborated on the studies showing therapeutic relevance of the inhibitors of hedgehog signaling in cancer. Evidence of the crosstalk of hedgehog signaling components with other signaling pathways and treatment resistance due to tumor heterogeneity have also been briefly discussed. Together, we have tried to put forward a compilation of the studies on therapeutic potential of hedgehog signaling in various cancers, specifically aggressive tumor types with a perspective into what is lacking and demands further investigation.

Sonic Hedgehog signaling pathway in gynecological and genitourinary cancer (Review)

Cancers of the urinary tract, as well as those of the female and male reproductive systems, account for a large percentage of malignancies worldwide. Mortality is frequently affected by late diagnosis or therapeutic difficulties. The Sonic Hedgehog (SHH) pathway is an evolutionary conserved molecular cascade, which is mainly associated with the development of the central nervous system in fetal life. The present review aimed to provide an in‑depth summary of the SHH signaling pathway, including the characterization of its major components, the mechanism of its upstream regulation and non‑canonical activation, as well as its interactions with other cellular pathways. In addition, the three possible mechanisms of the cellular SHH cascade in cancer tissue are discussed. The aim of the present review was to summarize significant findings with regards to the expression of the SHH pathway components in kidney, bladder, ovarian, cervical and prostate cancer. Reports associated with common deficits and de‑regulations of the SHH pathway were summarized, despite the differences in molecular and histological patterns among these malignancies. However, currently, neither are SHH pathway elements included in panels of prognostic/therapeutic molecular patterns in any of the discussed cancers, nor have the drugs targeting SMO or GLIs been approved for therapy. The findings of the present review may support future studies on the treatment of and/or molecular targets for gynecological and genitourinary cancers.

Expression of the Sonic Hedgehog pathway components in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common and the most aggressive histopathological subtype of kidney cancer, with patients exhibiting high mortality rates for metastatic tumors. The Sonic Hedgehog (SHH) pathway serves a crucial role in embryonic development. The abnormal activity of SHH signaling is observed in a broad range of malignancies. However, its role in ccRCC is still undetermined. The aim of the present study was to assess the expression of the SHH pathway genes in ccRCC. Neoplastic and morphologically unchanged kidney tissues were obtained during radical nephrectomy from 37 patients with ccRCC. The SHH, PTCH1, SMO and GLI1 mRNA levels were assessed using the reverse transcription-quantitative PCR. Western blot analysis was used to assess the full-length and C-terminal SHH protein level. The mRNA levels of SHH, SMO and GLI1 were approximately 2-, 2,5- and 7-fold higher in ccRCC tissue compared with control kidney tissue, respectively. Correlational analysis between the mRNA levels of SHH pathway genes and patients' clinicopathological factors revealed decreased and increased mRNA levels of PTCH1 and SMO respectively, in tumor samples derived from older patients (age >62). Furthermore, the level of C-terminal SHH protein in ccRCC samples was significantly lower in a group of males compared with females. No correlation was exhibited between molecular data and patient survival. Western blot analysis indicated a ~3-fold higher level of SHH full-length protein, and a 4-fold lower level of the C-terminal SHH protein domain, in ccRCC tumor tissues compared with normal kidney samples. The current study indicated an involvement of the SHH pathway in ccRCC development.

BCOR involvement in cancer

BCOR is a gene that encodes for an epigenetic regulator involved in the specification of cell differentiation and body structure development and takes part in the noncanonical polycomb repressive complex 1. This review provides a comprehensive summary of BCOR’s involvement in oncology, illustrating that various BCOR aberrations, such as the internal tandem duplications of the PCGF Ub-like fold discriminator domain and different gene fusions (mainly BCOR–CCNB3, BCOR–MAML3 and ZC3H7B–BCOR), represent driver elements of various sarcomas such as clear cell sarcoma of the kidney, primitive mesenchymal myxoid tumor of infancy, small round blue cell sarcoma, endometrial stromal sarcoma and histologically heterogeneous CNS neoplasms group with similar genomic methylation patterns known as CNS-HGNET-BCOR. Furthermore, other BCOR alterations (often loss of function mutations) recur in a large variety of mesenchymal, epithelial, neural and hematological tumors, suggesting a central role in cancer evolution.

MicroRNA-361-3p regulates retinoblastoma cell proliferation and stemness by targeting hedgehog signaling

Retinoblastoma (RB) is the most common type of intraocular malignancy in children. During RB oncogenesis, sonic hedgehog (SHH) is commonly differentially expressed. Additionally, microRNAs (miRs) are known to serve crucial roles as oncogenes or tumor suppressors. Specifically, miR-361-3p has been revealed to serve a vital role in cutaneous squamous cell carcinoma, cervical cancer, prostate cancer, colorectal cancer, gastric cancer, hepatocellular carcinoma, breast cancer and lung cancer. However, the role of miR-361-3p in RB and the potential molecular mechanisms involved remain unknown. Therefore, the current study aimed to determine the involvement of miR-361-3p in the development of RB by targeting SHH signaling. In the present study, miR-361-3p expression levels in RB tissue and serum samples obtained from 10 patients with RB, normal retinal tissue and serum samples obtained from 10 healthy controls, and two human RB cell lines (Y79 and Weri-Rb-1) were determined using reverse transcription-quantitative polymerase chain reaction. In addition, a cell counting kit-8 assay, a cell transfection assay, a MTT assay, western blotting, a tumor sphere formation assay and a luciferase assay were used to assess the expression, function and molecular mechanism of miR-361-3p in human RB. It was demonstrated that miR-361-3p was significantly downregulated in RB tissues, RB serum and RB cell lines compared with normal retinal tissues and normal serum. The ectopic expression of miR-361-3p decreased RB cell proliferation and stemness. Furthermore, GLI1 and GLI3 were verified as potential direct targets of miR-361-3p. miR-361-3p was also revealed to exhibit a negative correlation with GLI1/3 expression in RB samples. Taken together, the results indicate that miR-361-3p functions as a tumor suppressor in the carcinogenesis and progression of RB by targeting SHH signaling. Thus, miR-361-3p should be further assessed as a potential therapeutic target for RB treatment.

Blockade of sonic hedgehog signaling decreases viability and induces apoptosis in retinoblastoma cells: The key role of the PI3K/Akt pathway

Retinoblastoma (RB) is the most common type of malignant intraocular cancer in teenagers. One of the proteins abnormally expressed during oncogenesis of RB is sonic hedgehog (SHH), which possesses the capability to selectively activate transcription factors of different genes. However, the detailed function of SHH in RB remains unknown. Thus, the present study sought to investigate the role of SHH in the development of RB. The human RB WERI-Rb-1 cell line was used as an in vitro model for the knockdown of SHH by a specific short hairpin RNA (shRNA). To assess the effect of SHH inhibition on cell growth and apoptosis, cell viability, colony formation and flow cytometry assays were conducted. WERI-Rb-1 cells transfected with an shRNA targeting SHH were treated with the phosphoinositide-3 kinase (PI3K)/Akt agonist insulin-like growth factor 1 (IGF-1) to investigate the possible mechanism by which SHH promotes RB. The present results revealed that the silencing of SHH induced G1 cell-cycle arrest and apoptosis in WERI-Rb-1 cells and led to a decrease in cell viability, indicating that SHH has a critical role in the determination of RB cell survival. Moreover, according to the results of the IGF-1 assays, suppression of PI3K/Akt was a prerequisite for SHH inhibition, illuminating its potential role in the treatment of RB. The findings outlined in the present study elucidate a clear link between SHH and the PI3K/Akt pathway in RB cell survival, which could provide valuable inspiration for the advancement of therapies against RB.

PELI1 expression is correlated with MYC and BCL6 expression and associated with poor prognosis in diffuse large B-cell lymphoma

PELI is a family of E3 ubiquitin ligases that regulate protein activity through a post-translational modification, ubiquitination. While PELI1 has been found to play a pivotal role in inflammatory processes through the activation of Toll-like receptor signaling and the NF-kB pathway, the role of PELI1 in oncogenesis has not been the subject of much investigation. We aimed to explore PELI1 expression in various malignant lymphomas and identify clinicopathologic significance. Immunohistochemistry for PELI1 was performed on a total of 502 cases, including 406 B-cell, 76 T or NK-cell, and 20 Hodgkin lymphomas. High expression of PELI1 was found in high-grade B-cell lymphoma cases such as diffuse large B-cell lymphoma, Burkitt lymphoma, and plasmablastic lymphoma, whereas low-grade B-cell lymphoma, T/NK-cell lymphoma, and Hodgkin lymphoma cases showed very low levels of expression. In vitro cell line studies, the results of western blot, and RT-PCR were concordant with those of the immunohistochemical results; RL7, Pfeiffer, SUDHL-2, DOHH2, and Ramos cell lines showed high levels of PELI1 protein and mRNA expression. In 182 diffuse large B-cell lymphoma, PELI1 expression was positively correlated with the expression of MYC, BCL6, BCL2, and MUM1 (Spearman's ρ=0.427, 0.507, 0.246, and 0.137, respectively; P<0.001, <0.001, 0.001, and 0.066, respectively). In diffuse large B-cell lymphoma, high expression of PELI1 was associated with frequent bone marrow involvement (P=0.013) and shorter relapse-free survival (P=0.002). Our results suggest that PELI1 might participate in B-cell maturation or oncogenic activation of aggressive B-cell lymphomas, both during and after germinal center stages.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

May Sonic Hedgehog proteins be markers for malignancy in uterine smooth muscle tumors?

Several studies have demonstrated that the Sonic Hedgehog signaling pathway (SHH) plays an important role in tumorigenesis and cellular differentiation. We analyzed the protein expression of SHH pathway components and evaluated whether their profile could be useful for the diagnosis, prognosis, or prediction of the risk of malignancy for uterine smooth muscle tumors (USMTs). A total of 176 samples (20 myometrium, 119 variants of leiomyoma, and 37 leiomyosarcoma) were evaluated for the protein expression of the SHH signaling components, HHIP1 (SHH inhibitor), and BMP4 (SHH target) by immunohistochemistry. Western blot analysis was performed to verify the specificity of the antibodies. We grouped leiomyoma samples into conventional leiomyomas and unusual leiomyomas that comprise atypical, cellular, mitotically active leiomyomas and uterine smooth muscle tumors of uncertain malignant potential. Immunohistochemical analysis showed that SMO, SUFU, GLI1, GLI3, and BMP4 expression gradually increased depending on to the histologic tissue type. The protein expression of SMO, SUFU, and GLI1 was increased in unusual leiomyoma and leiomyosarcoma samples compared to normal myometrium. The inhibitor HHIP1 showed higher expression in myometrium, whereas only negative or basal expression of SMO, SUFU, GLI1, and GLI3 was detected in these samples. Strong expression of SHH was associated with poorer overall survival. Our data suggest that the expression of SHH proteins can be useful for evaluating the potential risk of malignancy for USMTs. Moreover, GLI1 and SMO may serve as future therapeutic targets for women with USMTs.

The bone marrow metastasis niche in retinoblastoma

BACKGROUND

Retinoblastoma (Rb) is a progressive cancer which mainly occurs in children, and which is caused by different genetic or epigenetic alterations that lead to inactivation of both alleles of the RB1 gene. Hereditary and non-hereditary forms of Rb do exist, and the hereditary form is associated with an increased risk of secondary malignancies. Metastasis to distant organs is a critical feature of many tumors, and may be caused by various molecular alterations at different stages. Recognition of these alterations and, thus, insight into the processes underlying the development of metastases may result in novel preventive as well as effective targeted treatment options. Rb is associated with metastases to various organs and tissues, including the bone marrow (BM).

METHODS

Here, we provide an overview of mutations and other molecular changes known to be involved in Rb development and metastasis to the BM. This overview is based on a literature search ranging from 1990 to 2015.

CONCLUSIONS

The various BM metastasis-related molecular changes identified to date may be instrumental for a better diagnosis, prognosis and classification of Rb patients, as well as for the development of novel comprehensive (targeted) therapies.