A Novel PTCH1 Frameshift Mutation Leading to Nevoid Basal Cell Carcinoma Syndrome

Sufu- and Spop-mediated regulation of Gli2 is essential for the control of mammalian cochlear hair cell differentiation

Development of mammalian auditory epithelium, the organ of Corti, requires precise control of both cell cycle withdrawal and differentiation. Sensory progenitors (prosensory cells) in the cochlear apex exit the cell cycle first but differentiate last. Sonic hedgehog (Shh) signaling is required for the spatiotemporal regulation of prosensory cell differentiation, but the underlying mechanisms remain unclear. Here, we show that suppressor of fused (Sufu), a negative regulator of Shh signaling, is essential for controlling the timing and progression of hair cell (HC) differentiation. Removal of Sufu leads to abnormal Atoh1 expression and a severe delay of HC differentiation due to elevated Gli2 mRNA expression. Later in development, HC differentiation defects are restored in the Sufu mutant by the action of speckle-type PDZ protein (Spop), which promotes Gli2 protein degradation. Deletion of both Sufu and Spop results in robust Gli2 activation, exacerbating HC differentiation defects. We further demonstrate that Gli2 inhibits HC differentiation through maintaining the progenitor state of Sox2⁺ prosensory cells. Along the basal-apical axis of the developing cochlea, the Sox2 expression level is higher in the progenitor cells than in differentiating cells and is down-regulated from base to apex as differentiation proceeds. The dynamic spatiotemporal change of Sox2 expression levels is controlled by Shh signaling through Gli2. Together, our results reveal key functions of Gli2 in sustaining the progenitor state, thereby preventing HC differentiation and in turn governing the basal-apical progression of HC differentiation in the cochlea.

Periocular Pigmented Basal Cell Carcinomas: Clinicopathologic Features and Mutational Profile

PURPOSE

Pigmented basal cell carcinomas (PBCC) is an uncommon variant of basal cell carcinoma of the periocular region with limited information in the literature. We highlight the clinicopathological profile and somatic mutations in periocular PBCC.

METHODS

The clinicopathological features and somatic mutations in patients with periocular PBCC were examined and compared with periocular non-PBCC reported in the literature. Next-generation sequencing panel analysis for the excised tumors identified somatic mutations.

RESULTS

In a total of 31 patients, PBCC was common in females (54%; p = 0.03); as a unilateral lower eyelid (n = 22; 71%), solitary mass (n = 30; 98%). Pathologic subtypes were variable. Most were nodular or mixed variants (n = 23; 74%). During the follow up (2.5-4.5 years), 1 patient (3.5%) had a recurrence. The clinical and pathologic features of PBCC were similar to those reported in nonperiocular locations. Somatic mutations detected in 25/31 tumors. Variants in 50/161 genes in the panel were noted. PTCH1 (14/31), TERT (12/31), and SMO (7/31) variants were common. Fifteen patients had novel drivers, including POLE, FANCD2, and CREBBP. SMO mutations were significantly more common in females (7/7), lower eyelid (5/7), and TERT mutations were more common in nodular subtype (10/12).

CONCLUSIONS

In this large cohort of a relatively uncommon variant of BCC, the clinicopathological features and tumor behavior of PBCC was similar to periocular non-PBCC. The somatic mutation spectrum of PBCC resembles that reported in nonperiocular cutaneous BCC with novel drivers identified. We identified several potential actionable mutations that could be targeted with molecular therapy.

Recent Advances in Signaling Pathways Comprehension as Carcinogenesis Triggers in Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common malignant skin tumor. BCC displays a different behavior compared with other neoplasms, has a slow evolution, and metastasizes very rarely, but sometimes it causes an important local destruction. Chronic ultraviolet exposure along with genetic factors are the most important risk factors involved in BCC development. Mutations in the PTCH1 gene are associated with Gorlin syndrome, an autosomal dominant disorder characterized by the occurrence of multiple BCCs, but are also the most frequent mutations observed in sporadic BCCs. PTCH1 encodes for PTCH1 protein, the most important negative regulator of the Hedgehog (Hh) pathway. There are numerous studies confirming Hh pathway involvement in BCC pathogenesis. Although Hh pathway has been intensively investigated, it remains incompletely elucidated. Recent studies on BCC tumorigenesis have shown that in addition to Hh pathway, there are other signaling pathways involved in BCC development. In this review, we present recent advances in BCC carcinogenesis.

Surgical management of non melanoma skin cancer of the head and neck

Non-melanoma skin cancer (NMSC) is the most common malignancy in the world and is reaching epidemic proportions. The most common types of NMSC include basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). The head and neck is the most common site for NMSC, and surgery remains the mainstay of treatment. We review the etiology, risk factors, pathogenesis as well as the preoperative, operative, and postoperative considerations in the management of NMSC. Multidisciplinary evaluation and attention to each of these phases is imperative for favorable oncologic and functional patient outcomes.

Identification of critically carcinogenesis-related genes in basal cell carcinoma

Background

Basal cell carcinoma (BCC) is a frequent malignant tumor of skin cancers with high morbidity. The objective of this study was to identify critical genes and pathways related to the carcinogenesis of BCC and gain more insights into the underlying molecular mechanisms of BCC.

Materials and methods

The gene expression profiles of GSE7553 and GSE103439 were downloaded from the Gene Expression Omnibus database with 19 tumors and 6 normal skin tissues. Differentially expressed genes (DEGs) were screened between BCC samples and normal tissues, followed by gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Subsequently, protein–protein interaction (PPI) network was constructed for these DEGs, and module analysis was performed.

Results

A total of 313 DEGs were obtained. Among them, 222 genes were upregulated and 91 genes were downregulated. Enrichment analysis indicated that the upregulated genes were significantly enriched in cell cycle and mitosis, while the downregulated genes were mainly associated with unsaturated fatty acid metabolic process and cell differentiation. In addition, TOP2A, CDK1, and CCNB1 were identified as the top three hub genes ranked by degrees in the PPI network. Meanwhile, three subnetworks were derived, which indicated that these DEGs were significantly enriched in pathways, including “cell cycle”, “extracellular matrix–receptor interaction”, “basal cell carcinoma”, and “hedgehog signaling pathway”.

Conclusions

The novel critical DEGs and pathways identified in this study may serve pivotal roles in the carcinogenesis of BCC and indicate more molecular targets for the treatment of BCC.