AXIN1 bi-allelic variants disrupting the C-terminal DIX domain cause craniometadiaphyseal osteosclerosis with hip dysplasia.

Sclerosing skeletal dysplasias result from an imbalance between bone formation and resorption. We identified three homozygous, C-terminally truncating AXIN1 variants in seven individuals from four families affected by macrocephaly, cranial hyperostosis, and vertebral endplate sclerosis. Other frequent findings included hip dysplasia, heart malformations, variable developmental delay, and hematological anomalies. In line with AXIN1 being a central component of the ß-catenin destruction complex, analyses of primary and genome-edited cells harboring the truncating variants revealed enhanced basal canonical Wnt pathway activity. All three AXIN1-truncating variants resulted in reduced protein levels and impaired AXIN1 polymerization mediated by its C-terminal DIX domain but partially retained Wnt-inhibitory function upon overexpression. Addition of a tankyrase inhibitor attenuated Wnt overactivity in the AXIN1-mutant model systems. Our data suggest that AXIN1 coordinates the action of osteoblasts and osteoclasts and that tankyrase inhibitors can attenuate the effects of AXIN1 hypomorphic variants.

Heterozygous truncating variants in SUFU cause congenital ocular motor apraxia.

PURPOSE: This study aimed to delineate the genetic basis of congenital ocular motor apraxia (COMA) in patients not otherwise classifiable. METHODS: We compiled clinical and neuroimaging data of individuals from six unrelated families with distinct clinical features of COMA who do not share common diagnostic characteristics of Joubert syndrome or other known genetic conditions associated with COMA. We used exome sequencing to identify pathogenic variants and functional studies in patient-derived fibroblasts. RESULTS: In 15 individuals, we detected familial as well as de novo heterozygous truncating causative variants in the Suppressor of Fused (SUFU) gene, a negative regulator of the Hedgehog (HH) signaling pathway. Functional studies showed no differences in cilia occurrence, morphology, or localization of ciliary proteins, such as smoothened. However, analysis of expression of HH signaling target genes detected a significant increase in the general signaling activity in COMA patient-derived fibroblasts compared with control cells. We observed higher basal HH signaling activity resulting in increased basal expression levels of GLI1, GLI2, GLI3, and Patched1. Neuroimaging revealed subtle cerebellar changes, but no full-blown molar tooth sign. CONCLUSION: Taken together, our data imply that the clinical phenotype associated with heterozygous truncating germline variants in SUFU is a forme fruste of Joubert syndrome.

Oncogenic NRAS Accelerates Rhabdomyosarcoma Formation When Occurring within a Specific Time Frame during Tumor Development in Mice.

In the Ptch+/- mouse model for embryonal rhabdomyosarcoma (ERMS), we recently showed that oncogenic (onc) H-, K- or NRAS mutations do not influence tumor growth when induced at the advanced, full-blown tumor stage. However, when induced at the invisible ERMS precursor stage at 4 weeks of age, tumor development was enforced upon oncHRAS and oncKRAS but not by oncNRAS, which instead initiated tumor differentiation. These data indicate that oncRAS-associated processes differ from each other in dependency on the isoform and their occurrence during tumor development. Here, we investigated the outcome of oncNRAS induction at an earlier ERMS precursor stage at 2 weeks of age. In this setting, oncNRAS accelerates tumor growth because it significantly shortens the ERMS-free survival and increases the ERMS incidence. However, it does not seem to alter the differentiation of the tumors. It is also not involved in tumor initiation. Together, these data show that oncNRAS mutations can accelerate tumor growth when targeting immature ERMS precursors within a specific time window, in which the precursors are permissive to the mutation and show that oncNRAS-associated processes differ from each other in dependency on their occurrence during tumor development.

Hypothalamic sonic hedgehog is required for cell specification and proliferation of LHX3/LHX4 pituitary embryonic precursors.

Sonic hedgehog (SHH) is an essential morphogenetic signal that dictates cell fate decisions in several developing organs in mammals. In vitro data suggest that SHH is required to specify LHX3+/LHX4+ Rathke's pouch (RP) progenitor identity. However, in vivo studies have failed to reveal such a function, supporting instead a crucial role for SHH in promoting proliferation of these RP progenitors and for differentiation of pituitary cell types. Here, we have used a genetic approach to demonstrate that activation of the SHH pathway is necessary to induce LHX3+/LHX4+ RP identity in mouse embryos. First, we show that conditional deletion of Shh in the anterior hypothalamus results in a fully penetrant phenotype characterised by a complete arrest of RP development, with lack of Lhx3/Lhx4 expression in RP epithelium at 9.0 days post coitum (dpc) and total loss of pituitary tissue by 12.5 dpc. Conversely, overactivation of the SHH pathway by conditional deletion of Ptch1 in RP progenitors leads to severe hyperplasia and enlargement of the Sox2+ stem cell compartment by the end of gestation.

Spreading of Isolated Ptch Mutant Basal Cell Carcinoma Precursors Is Physiologically Suppressed and Counteracts Tumor Formation in Mice.

Basal cell carcinoma (BCC) originate from Hedgehog/Patched signaling-activated epidermal stem cells. However, the chemically induced tumorigenesis of mice with a CD4Cre-mediated biallelic loss of the Hedgehog signaling repressor Patched also induces BCC formation. Here, we identified the cellular origin of CD4Cre-targeted BCC progenitors as rare Keratin 5+ epidermal cells and show that wildtype Patched offspring of these cells spread over the hair follicle/skin complex with increasing mouse age. Intriguingly, Patched mutant counterparts are undetectable in age-matched untreated skin but are getting traceable upon applying the chemical tumorigenesis protocol. Together, our data show that biallelic Patched depletion in rare Keratin 5+ epidermal cells is not sufficient to drive BCC development, because the spread of these cells is physiologically suppressed. However, bypassing the repression of Patched mutant cells, e.g., by exogenous stimuli, leads to an accumulation of BCC precursor cells and, finally, to tumor development.

Insights into pediatric rhabdomyosarcoma research: Challenges and goals.

Overall survival rates for pediatric patients with high-risk or relapsed rhabdomyosarcoma (RMS) have not improved significantly since the 1980s. Recent studies have identified a number of targetable vulnerabilities in RMS, but these discoveries have infrequently translated into clinical trials. We propose streamlining the process by which agents are selected for clinical evaluation in RMS. We believe that strong consideration should be given to the development of combination therapies that add biologically targeted agents to conventional cytotoxic drugs. One example of this type of combination is the addition of the WEE1 inhibitor AZD1775 to the conventional cytotoxic chemotherapeutics, vincristine and irinotecan.

A Functional and Putative Physiological Role of Calcitriol in Patched1/Smoothened Interaction.

The Patched1 (Ptch)-mediated inhibition of Smoothened (Smo) is still an open question. However, a direct Ptch/Smo interaction has been excluded, Smo modulators were identified, but the endogenous signal transmitting molecule remains undiscovered. Here, we demonstrate that calcitriol, the hormonally active form of vitamin D3, is an excellent candidate for transmission of Ptch/Smo interaction. Our study reveals that Ptch expression is sufficient to release calcitriol from the cell and that calcitriol inhibits Smo action and ciliary translocation by acting on a site distinct from the 7-transmembrane domain or the cysteine-rich domain. Moreover calcitriol strongly synergizes with itraconazole (ITZ) in Smo inhibition, which did not result from elevated calcitriol bioavailability due to ITZ-mediated 24-hydroxylase inhibition but rather from a direct interaction of the compounds at the level of Smo. Together, we suggest that calcitriol represents a possible endogenous transmitter of Ptch/Smo interaction. Moreover calcitriol or calcitriol derivatives combined with ITZ might be a treatment option of Hedgehog-associated cancers.

Inactivation of Patched1 in mice leads to development of gastrointestinal stromal-like tumors that express Pdgfrα but not kit.

BACKGROUND & AIMS: A fraction of gastrointestinal stromal tumor (GIST) cells overexpress the platelet-derived growth factor receptor (PDGFR)A, although most overexpress KIT. It is not known if this is because these receptor tyrosine kinases have complementary oncogenic potential, or because of heterogeneity in the cellular origin of GIST. Little also is known about why Hedgehog (HH) signaling is activated in some GIST. HH binds to and inactivates the receptor protein patched homolog (PTCH). METHODS: Ptch was conditionally inactivated in mice (to achieve constitutive HH signaling) using a Cre recombinase regulated by the lysozyme M promoter. Cre-expressing cells were traced using R26R-LacZ reporter mice. Tumors were characterized by in situ hybridization, immunohistochemistry, immunoblot, and quantitative reverse-transcriptase polymerase chain reaction analyses. Cell transformation was assessed by soft agar assay. RESULTS: Loss of Ptch from lysozyme M-expressing cells resulted in the development of tumors of GIST-like localization and histology; these were reduced when mice were given imatinib, a drug that targets KIT and PDGFRA. The Hh signaling pathway was activated in the tumor cells, and Pdgfrα, but not Kit, was overexpressed and activated. Lineage tracing revealed that Cre-expressing intestinal cells were Kit-negative. These cells sometimes expressed Pdgfrα and were located near Kit-positive interstitial cells of Cajal. In contrast to KIT, activation of PDGFRA increased anchorage-independent proliferation and was required for tumor formation in mice by cells with activated HH signaling. CONCLUSIONS: Inactivation of Ptch in mice leads to formation of GIST-like tumors that express Pdgfrα, but not Kit. Activation of Pdgfrα signaling appears to facilitate tumorigenesis.

Interaction of hedgehog and vitamin D signaling pathways in basal cell carcinomas.

Basal Cell Carcinomas (BCCs) are the most commonly diagnosed tumors among people in the western world. Most BCCs are caused by mutational inactivation of the tumor suppressor Patched (PTCH), which results in activation of Smoothened (SMO) and of the Hedgehog (HH) signaling pathway. Recent studies indicate that BCC progression involves a crosstalk between Hh signaling, vitamin D derivatives and the vitamin D receptor (Vdr) signaling pathway. This has been demonstrated in BCC-bearing Ptch mutant mice and BCC cell lines, in which both vitamin D3 and its active metabolite calcitriol (1alpha-25(OH)2D3) exert antitumor effects. Interestingly, the antitumor effects are mainly ascribed to an inhibition of Hh signaling. Furthermore, as evident from studies in Vdr deficient mice, calcitriol may also repress the activity of Hh signaling in a Vdr-dependent fashion thereby establishing an additional inhibitory feedback on Hh signaling activity. In this chapter, we discuss the current understanding and controversial findings of the inhibition of Hh signaling by vitamin D derivatives and the implication of these findings for BCC carcinogenesis.

Hedgehog signalling stimulates precursor cell accumulation and impairs epithelial maturation in the murine oesophagus.

OBJECTIVE: In the intestine Hedgehog (Hh) signalling is directed from epithelium to mesenchyme and negatively regulates epithelial precursor cell fate. The role of Hh signalling in the oesophagus has not been studied in vivo. Here the authors examined the role of Hh signalling in epithelial homeostasis of oesophagus. DESIGN: The authors used transgenic mice in which the Hh receptor Patched1 (Ptch1) could be conditionally inactivated in a body-wide manner and mice in which Gli1 could be induced specifically in the epithelium of the skin and oesophagus. Effects on epithelial homeostasis of the oesophagus were examined using immunohistochemistry, in situ hybridisation, transmission electron microscopy and real-time PCR. Hh signalling was examined in patients with oesophageal squamous cell carcinoma (SCC) by quantitative real-time PCR. RESULTS: Sonic Hh is signalled in an autocrine manner in the basal layer of the oesophagus. Activation of Hh signalling resulted in an expansion of the epithelial precursor cell compartment and failure of epithelial maturation and migration. Levels of Hh targets GLI1, HHIP and PTCH1 were increased in SCC compared with normal tissue from the same patients. CONCLUSION: Here the authors find that Hh signalling positively regulates the precursor cell compartment in the oesophageal epithelium in an autocrine manner. Since Hh signalling targets precursor cells in the oesophageal epithelium and signalling is increased in SCCs, Hh signalling may be involved in oesophageal SCC formation.

Empty liposomes induce antitumoral effects associated with macrophage responses distinct from those of the TLR1/2 agonist Pam3CSK 4 (BLP).

Liposomes are frequently used in cancer therapy to encapsulate and apply anticancer drugs. Here, we show that a systemic treatment of mice bearing skin tumors with empty phosphatidylcholine liposomes (PCL) resulted in inhibition of tumor growth, which was similar to that observed with the synthetic bacterial lipoprotein and TLR1/2 agonist Pam(3)CSK(4) (BLP). Both compounds led to a substantial decrease of macrophages in spleen and in the tumor-bearing skin. Furthermore, both treatments induced the expression of typical macrophage markers in the tumor-bearing tissue. As expected, BLP induced the expression of the M1 marker genes Cxcl10 and iNOS, whereas PCL, besides inducing iNOS, also increased the M2 marker genes Arg1 and Trem2. In vitro experiments demonstrated that neither PCL nor BLP influenced proliferation or survival of tumor cells, whereas both compounds inhibited proliferation and survival and increased the migratory capacity of bone marrow-derived macrophages (BMDM). However, in contrast to BLP, PCL did not activate cytokine secretion and induced a different BMDM phenotype. Together, the data suggest that similar to BLP, PCL induce an antitumor response by influencing the tumor microenvironment, in particular by functional alterations of macrophages, however, in a distinct manner from those induced by BLP.

T cell development critically depends on prethymic stromal patched expression.

We recently described that T cell specification in mice deficient in the Hedgehog (Hh) receptor Patched (Ptch) is blocked at the level of the common lymphoid progenitor in the bone marrow (BM). Adoptive transfer of wild-type BM in Ptch-deficient mice provides evidence that T cell development strictly depends on Ptch expression in the nonhematopoietic compartment. Transplantation experiments using BM deficient in the glucocorticoid receptor exclude any involvement of the stress hormone corticosterone in our model. Using cell-type-specific knockout mice, we show that T cell development is independent of T cell-intrinsic Ptch expression. Furthermore, Ptch expression by the thymus stroma is dispensable, as revealed by fetal thymus organ culture and thymus transplantation. In contrast, analysis of the earliest thymic progenitors in Ptch-deficient mice indicated that Ptch is required for the development or supply of thymic homing progenitors that give rise to earliest thymic progenitors. Collectively, our findings identified Ptch as an exclusive T cell-extrinsic factor necessary for proper development of T cells at their prethymic stage. This observation may be important for current considerations using Hh inhibitors upstream of Ptch in diseases accompanied by aberrant Hh signaling.

The hidden hedgehog of the pituitary: hedgehog signaling in development, adulthood and disease of the hypothalamic-pituitary axis.

Hedgehog signaling plays pivotal roles in embryonic development, adult homeostasis and tumorigenesis. However, its engagement in the pituitary gland has been long underestimated although Hedgehog signaling and pituitary embryogenic development are closely linked. Thus, deregulation of this signaling pathway during pituitary development results in malformation of the gland. Research of the last years further implicates a regulatory role of Hedgehog signaling in the function of the adult pituitary, because its activity is also interlinked with homeostasis, hormone production, and most likely also formation of neoplasms of the gland. The fact that this pathway can be efficiently targeted by validated therapeutic strategies makes it a promising candidate for treating pituitary diseases. We here summarize the current knowledge about the importance of Hedgehog signaling during pituitary development and review recent data that highlight the impact of Hedgehog signaling in the healthy and the diseased adult pituitary gland.

Calcitriol inhibits hedgehog signaling and induces vitamin d receptor signaling and differentiation in the patched mouse model of embryonal rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Aberrant Hedgehog (Hh) signaling is characteristic of the embryonal subtype (ERMS) and of fusion-negative alveolar RMS. In the mouse, ERMS-like tumors can be induced by mutations in the Hh receptor Patched1 (Ptch). As in humans these tumors show increased Hh pathway activity. Here we demonstrate that the treatment with the active form of vitamin D(3), calcitriol, inhibits Hh signaling and proliferation of murine ERMS in vivo and in vitro. Concomitantly, calcitriol activates vitamin D receptor (Vdr) signaling and induces tumor differentiation. In addition, calcitriol inhibits ERMS growth in Ptch-mutant mice, which is, however, a rather late response. Taken together, our results suggest that exogenous supply of calcitriol could be beneficial in the treatment of RMS, especially in those which are associated with aberrant Hh signaling activity.

Tumor suppressive functions of WNT5A in rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is a highly aggressive soft tissue malignancy that predominantly affects children. The main subtypes are alveolar RMS (ARMS) and embryonal RMS (ERMS) and the two show an impaired muscle differentiation phenotype. One pathway involved in muscle differentiation is WNT signaling. However, the role of this pathway in RMS is far from clear. Our recent data showed that the canonical WNT/ß­Catenin pathway serves a subordinate role in RMS, whereas non­canonical WNT signaling probably is more important for this tumor entity. The present study investigated the role of WNT5A, which is the major ligand of non­canonical WNT signaling, in ERMS and ARMS. Gene expression analysis showed that WNT5A was expressed in human RMS samples and that its expression is more pronounced in ERMS. When stably overexpressed in RMS cell lines, WNT5A decreased proliferation and migration of the cells as demonstrated by BrdU incorporation and Transwell migration or scratch assay, respectively. WNT5A also decreased the self­renewal capacity and the expression of stem cell markers and modulates the levels of muscle differentiation markers as shown by sphere assay and western blot analysis, respectively. Finally, overexpression of WNT5A can destabilize active ß­Catenin of RMS cells. A WNT5A knockdown has opposite effects. Together, the results suggest that WNT5A has tumor suppressive functions in RMS, which accompanies downregulation of ß­Catenin.

Hedgehog signaling in endocrine and folliculo-stellate cells of the adult pituitary.

Ubiquitous overactivation of Hedgehog signaling in adult pituitaries results in increased expression of proopiomelanocortin (Pomc), growth hormone (Gh) and prolactin (Prl), elevated adrenocorticotropic hormone (Acth) production and proliferation of Sox2+ cells. Moreover, ACTH, GH and PRL-expressing human pituitary adenomas strongly express the Hedgehog target GLI1. Accordingly, Hedgehog signaling seems to play an important role in pathology and probably also in homeostasis of the adult hypophysis. However, the specific Hedgehog-responsive pituitary cell type has not yet been identified. We here investigated the Hedgehog pathway activation status and the effects of deregulated Hedgehog signaling cell-specifically in endocrine and non-endocrine pituitary cells. We demonstrate that Hedgehog signaling is unimportant for the homeostasis of corticotrophs, whereas it is active in subpopulations of somatotrophs and folliculo-stellate cells in vivo. Reinforcement of Hedgehog signaling activity in folliculo-stellate cells stimulates growth hormone production/release from somatotrophs in a paracrine manner, which most likely is mediated by the neuropeptide vasoactive intestinal peptide. Overall, our data show that Hedgehog signaling affects the homeostasis of pituitary hormone production via folliculo-stellate cell-mediated regulation of growth hormone production/secretion.

Context-dependent modulation of aggressiveness of pediatric tumors by individual oncogenic RAS isoforms.

A prototypic pediatric cancer that frequently shows activation of RAS signaling is embryonal rhabdomyosarcoma (ERMS). ERMS also show aberrant Hedgehog (HH)/GLI signaling activity and can be driven by germline mutations in this pathway. We show, that in ERMS cell lines derived from sporadic tumors i.e. from tumors not caused by an inherited genetic variant, HH/GLI signaling plays a subordinate role, because oncogenic mutations in HRAS, KRAS, or NRAS (collectively named oncRAS) inhibit the main HH target GLI1 via the MEK/ERK-axis, but simultaneously increase proliferation and tumorigenicity. oncRAS also modulate expression of stem cell markers in an isoform- and context-dependent manner. In Hh-driven murine ERMS that are caused by a Patched mutation, oncHRAS and mainly oncKRAS accelerate tumor development, whereas oncNRAS induces a more differentiated phenotype. These features occur when the oncRAS mutations are induced at the ERMS precursor stage, but not when induced in already established tumors. Moreover, in contrast to what is seen in human cell lines, oncRAS mutations do not alter Hh signaling activity and marginally affect expression of stem cell markers. Together, all three oncRAS mutations seem to be advantageous for ERMS cell lines despite inhibition of HH signaling and isoform-specific modulation of stem cell markers. In contrast, oncRAS mutations do not inhibit Hh-signaling in Hh-driven ERMS. In this model, oncRAS mutations seem to be advantageous for specific ERMS populations that occur within a specific time window during ERMS development. In addition, this window may be different for individual oncRAS isoforms, at least in the mouse.

Mechanochemical control of epidermal stem cell divisions by B-plexins.

The precise spatiotemporal control of cell proliferation is key to the morphogenesis of epithelial tissues. Epithelial cell divisions lead to tissue crowding and local changes in force distribution, which in turn suppress the rate of cell divisions. However, the molecular mechanisms underlying this mechanical feedback are largely unclear. Here, we identify a critical requirement of B-plexin transmembrane receptors in the response to crowding-induced mechanical forces during embryonic skin development. Epidermal stem cells lacking B-plexins fail to sense mechanical compression, resulting in disinhibition of the transcriptional coactivator YAP, hyperproliferation, and tissue overgrowth. Mechanistically, we show that B-plexins mediate mechanoresponses to crowding through stabilization of adhesive cell junctions and lowering of cortical stiffness. Finally, we provide evidence that the B-plexin-dependent mechanochemical feedback is also pathophysiologically relevant to limit tumor growth in basal cell carcinoma, the most common type of skin cancer. Our data define a central role of B-plexins in mechanosensation to couple cell density and cell division in development and disease.

Depletion of the colonic epithelial precursor cell compartment upon conditional activation of the hedgehog pathway.

BACKGROUND & AIMS: The intestinal epithelium is a homeostatic system in which differentiated cells are in dynamic equilibrium with rapidly cycling precursor cells. Wnt signaling regulates intestinal epithelial precursor cell fate and proliferation. Homeostatic systems exist by virtue of negative feedback loops, and we have previously identified the Hedgehog (Hh) pathway as a potential negative feedback signal in the colonic epithelium. Indian hedgehog (Ihh) is produced by the differentiated enterocytes and negatively regulates Wnt signaling in intestinal precursor cells. We studied the role of members of the Hh signaling family in the intestine using a conditional genetic approach. METHODS: We inactivated the Hh receptor Patched1 (Ptch1) in adult mice, resulting in constitutive activation of the Hh signaling pathway. Effects on colonic mucosal homeostasis were examined. Colon tissues were examined by immunohistochemistry, in situ hybridization, transmission electron microscopy, and real-time polymerase chain reaction. RESULTS: Ihh but not Sonic hedgehog (Shh) was expressed in colonic epithelium. Expression of Ptch1 and Gli1 was restricted to the mesenchyme. Constitutive activation of Hh signaling resulted in accumulation of myofibroblasts and colonic crypt hypoplasia. A reduction in the number of epithelial precursor cells was observed with premature development into the enterocyte lineage and inhibition of Wnt signaling. Activation of Hh signaling resulted in induction of the expression of bone morphogenetic proteins (Bmp) and increased Bmp signaling in the epithelium. CONCLUSIONS: Hh signaling acts in a negative feedback loop from differentiated cells via the mesenchyme to the colonic epithelial precursor cell compartment in the adult mouse.

WIF1 Suppresses the Generation of Suprabasal Cells in Acanthotic Skin and Growth of Basal Cell Carcinomas upon Forced Overexpression.

We analyzed the role of WIF1 in normal and acanthotic epidermis of 12-O-tetradecanoylphorbol-13-acetate (TPA) or all-trans-retinoic acid (ATRA)-treated and basal cell carcinoma (BCC)-bearing mice. WIF1 protein is located in the follicular infundibulum and interfollicular epidermis (IFE) in murine back skin. Within the hyperplastic epidermis of TPA- or ATRA-treated or BCC-bearing murine skin, WIF1 and Keratin 10 overlap in Ki67⁻ suprabasal layers, while basal epidermal layers expressing Ki67, and BCCs expressing Wif1 mRNA, are free of WIF1 protein. This is similar in human skin, with the exception that WIF1 protein is found in single Ki67⁻ basal epidermal cells in normal skin and additionally in Ki67+ cells in acanthotic skin. Wif1-deficiency enhances acanthosis of the murine BCC-associated epidermis, which is accompanied by an increase of Ki67+ and of Sca-1+ basal cells. WIF1 overexpression in allografted BCC-derived keratinocytes prevents growth and keratinization, involving enhanced phosphorylation of protein kinase C and extracellular signal-regulated kinase 1 and arguably factors secreted by the in vivo environment. In summary, WIF1 protein marks suprabasal layers in the normal IFE. It is also present in the epidermis overlaying BCCs where it diminishes proliferation of basal cells and production of differentiating suprabasal cells. In addition, WIF1 can prevent proliferation and keratinization of BCC-related keratinocytes.