Differential expression of phosphorylated MEK and ERK correlates with aggressive BCC subtypes.

Basal cell carcinoma (BCC) is associated with aberrant Hedgehog (HH) signalling through mutational inactivation of PTCH1; however, there is conflicting data regarding MEK/ERK signalling in BCC and the signalling pathway interactions in these carcinomas. To address this, expression of active phospho (p) MEK and ERK was examined in a panel of 15 non-aggressive and 14 aggressive BCCs. Although not uniformly expressed, both phospho-proteins were detected in the nuclei and/or cytoplasm of normal and tumour-associated epidermal cells however, whereas phospho-MEK (pMEK) was present in all non-aggressive BCCs (14/14), phospho-ERK (pERK) was rarely expressed (2/14). In contrast pERK expression was more prevalent in aggressive tumours (11/14). Interestingly, pMEK was only localized to the tumour mass whereas pERK was expressed in tumours and stroma of aggressive BCCs. Similarly, pERK (but not pMEK) was absent in mouse BCC-like tumours derived from X-ray irradiated Ptch1+/- mice with stromal pERK observed in myofibroblasts of the aggressive variant as well as in the tumour mass. RNA sequencing analysis of tumour epithelium and stroma of aggressive and non-aggressive BCC revealed the upregulation of epidermal growth factor receptor- and ERK-related pathways. Angiogenesis and immune response pathways were also upregulated in the stroma compared with the tumour. PTCH1 suppressed NEB1 immortalized keratinocytes (shPTCH1) display upregulated pERK that can be independent of MEK expression. Furthermore, epidermal growth factor pathway inhibitors affect the HH pathway by suppressing GLI1. These studies reveal differential expression of pERK between human BCC subtypes that maybe active by a pathway independent of MEK.

Heterozygous mutation of sonic hedgehog receptor (Ptch1) drives cerebellar overgrowth and sex-specifically alters hippocampal and cortical layer structure, activity, and social behavior in female mice.

Sonic hedgehog (SHH) signaling is essential for the differentiation and migration of early stem cell populations during cerebellar development. Dysregulation of SHH-signaling can result in cerebellar overgrowth and the formation of the brain tumor medulloblastoma. Treatment for medulloblastoma is extremely aggressive and patients suffer life-long side effects including behavioral deficits. Considering that other behavioral disorders including autism spectrum disorders, holoprosencephaly, and basal cell nevus syndrome are known to present with cerebellar abnormalities, it is proposed that some behavioral abnormalities could be inherent to the medulloblastoma sequalae rather than treatment. Using a haploinsufficient SHH receptor knockout mouse model (Ptch1+/-), a partner preference task was used to explore activity, social behavior and neuroanatomical changes resulting from dysregulated SHH signaling. Compared to wild-type, Ptch1+/- females displayed increased activity by traveling a greater distance in both open-field and partner preference tasks. Social behavior was also sex-specifically modified in Ptch1+/- females that interacted more with both novel and familiar animals in the partner preference task compared to same-sex wild-type controls. Haploinsufficiency of PTCH1 resulted in cerebellar overgrowth in lobules IV/V and IX of both sexes, and female-specific decreases in hippocampal size and isocortical layer thickness. Taken together, neuroanatomical changes related to deficient SHH signaling may alter social behavior.

Sonic Hedgehog repression underlies gigaxonin mutation-induced motor deficits in giant axonal neuropathy.

Growing evidence shows that alterations occurring at early developmental stages contribute to symptoms manifested in adulthood in the setting of neurodegenerative diseases. Here, we studied the molecular mechanisms causing giant axonal neuropathy (GAN), a severe neurodegenerative disease due to loss-of-function of the gigaxonin-E3 ligase. We showed that gigaxonin governs Sonic Hedgehog (Shh) induction, the developmental pathway patterning the dorso-ventral axis of the neural tube and muscles, by controlling the degradation of the Shh-bound Patched receptor. Similar to Shh inhibition, repression of gigaxonin in zebrafish impaired motor neuron specification and somitogenesis and abolished neuromuscular junction formation and locomotion. Shh signaling was impaired in gigaxonin-null zebrafish and was corrected by both pharmacological activation of the Shh pathway and human gigaxonin, pointing to an evolutionary-conserved mechanism regulating Shh signaling. Gigaxonin-dependent inhibition of Shh activation was also demonstrated in primary fibroblasts from patients with GAN and in a Shh activity reporter line depleted in gigaxonin. Our findings establish gigaxonin as a key E3 ligase that positively controls the initiation of Shh transduction, and reveal the causal role of Shh dysfunction in motor deficits, thus highlighting the developmental origin of GAN.

Traitement médical des carcinomes basocellulaires avancés: Medical treatment of advanced basal cell carcinoma.

Until recently, advanced BCC were only accessible to a highly morbid surgery not necessarily proving to be carcinologic, and leaving terrible dysmorphic sequelae hard to accept by the patient. Another possibility, the only one in case of metastatic BCC, was chemotherapy which efficacy has never been proven in a clinical trial. Radiotherapy is most often not accessible because of previous radiotherapy or because of the localization or the extension of the lesion. The discovery of the importance of the sonic hedgehog pathway in the physiopathology of BCC has opened a new strategy with the development of targeted anti SMO drugs inactivating the pathway. Two molecules have become available following Phase I and II studies: vismodegib (Erivedge®) the first in class indicated for locally advanced and metastatic BCC and sonidegib (Odomzo®) indicated only for locally advanced BCC. The pharmacokinetic profiles of sonidegib and vismodegib showed several differences. No head to head comparative studies are available between these two drugs. Their pivotal phase II studies had similar study designs and endpoints. The objective response rate (ORR) by central review for vismodegib was 47.6% (95% CI 35.5-60.6) at 21 months follow-up. The ORR for sonidegib according to central review at 18 months follow-up is 56.1% (95% CI 43.3-68.3). Although both treatments share a similar adverse event profile with possible numerically differences in incidence, most patients will discontinue hedgehog inhibitors treatment in the long term because of side effects. Some resistant cases to these drugs have been described but are rather rare. In case of resistance or bad tolerability to the drug future hopes rely on immunotherapy currently under investigation. © 2018. Published by Elsevier Masson SAS. All rights reserved. Cet article fait partie du numéro supplément Prise en charge des carcinomes basocellulaires difficiles à traiter réalisé avec le soutien institutionnel de Sun Pharma.

PTCH1 is a reliable marker for predicting imatinib response in chronic myeloid leukemia patients in chronic phase.

Patched homolog 1 gene (PTCH1) expression and the ratio of PTCH1 to Smoothened (SMO) expression have been proposed as prognostic markers of the response of chronic myeloid leukemia (CML) patients to imatinib. We compared these measurements in a realistic cohort of 101 patients with CML in chronic phase (CP) using a simplified qPCR method, and confirmed the prognostic power of each in a competing risk analysis. Gene expression levels were measured in peripheral blood samples at diagnosis. The PTCH1/SMO ratio did not improve PTCH1 prognostic power (area under the receiver operating characteristic curve 0.71 vs. 0.72). In order to reduce the number of genes to be analyzed, PTCH1 was the selected measurement. High and low PTCH1 expression groups had significantly different cumulative incidences of imatinib failure (IF), which was defined as discontinuation of imatinib due to lack of efficacy (5% vs. 25% at 4 years, P = 0.013), probabilities of achieving a major molecular response (81% vs. 53% at first year, P = 0.02), and proportions of early molecular failure (14% vs. 43%, P = 0.015). Every progression to an advanced phase (n = 3) and CML-related death (n = 2) occurred in the low PTCH1 group (P<0.001 for both comparisons). PTCH1 was an independent prognostic factor for the prediction of IF. We also validated previously published thresholds for PTCH1 expression. Therefore, we confirmed that PTCH1 expression can predict the imatinib response in CML patients in CP by applying a more rigorous statistical analysis. Thus, PTCH1 expression is a promising molecular marker for predicting the imatinib response in CML patients in CP.

MicroRNA Biogenesis and Hedgehog-Patched Signaling Cooperate to Regulate an Important Developmental Transition in Granule Cell Development.

The Dicer1, Dcr-1 homolog (Drosophila) gene encodes a type III ribonuclease required for the canonical maturation and functioning of microRNAs (miRNAs). Subsets of miRNAs are known to regulate normal cerebellar granule cell development, in addition to the growth and progression of medulloblastoma, a neoplasm that often originates from granule cell precursors. Multiple independent studies have also demonstrated that deregulation of Sonic Hedgehog (Shh)-Patched (Ptch) signaling, through miRNAs, is causative of granule cell pathologies. In the present study, we investigated the genetic interplay between miRNA biogenesis and Shh-Ptch signaling in granule cells of the cerebellum by way of the Cre/lox recombination system in genetically engineered models of Mus musculus (mouse). We demonstrate that, although the miRNA biogenesis and Shh-Ptch-signaling pathways, respectively, regulate the opposing growth processes of cerebellar hypoplasia and hyperplasia leading to medulloblastoma, their concurrent deregulation was nonadditive and did not bring the growth phenotypes toward an expected equilibrium. Instead, mice developed either hypoplasia or medulloblastoma, but of a greater severity. Furthermore, some genotypes were bistable, whereby subsets of mice developed hypoplasia or medulloblastoma. This implies that miRNAs and Shh-Ptch signaling regulate an important developmental transition in granule cells of the cerebellum. We also conclusively show that the Dicer1 gene encodes a haploinsufficient tumor suppressor gene for Ptch1-induced medulloblastoma, with the monoallielic loss of Dicer1 more severe than biallelic loss. These findings exemplify how genetic interplay between pathways may produce nonadditive effects with a substantial and unpredictable impact on biology. Furthermore, these findings suggest that the functional dosage of Dicer1 may nonadditively influence a wide range of Shh-Ptch-dependent pathologies.