Wnt signaling is one of the key oncogenic pathways in multiple cancers, and targeting this pathway is an attractive therapeutic approach. However, therapeutic success has been limited because of the lack of therapeutic agents for targets in the Wnt pathway and the lack of a defined patient population that would be sensitive to a Wnt inhibitor. We developed a screen for small molecules that block Wnt secretion. This effort led to the discovery of LGK974, a potent and specific small-molecule Porcupine (PORCN) inhibitor. PORCN is a membrane-bound O-acyltransferase that is required for and dedicated to palmitoylation of Wnt ligands, a necessary step in the processing of Wnt ligand secretion. We show that LGK974 potently inhibits Wnt signaling in vitro and in vivo, including reduction of the Wnt-dependent LRP6 phosphorylation and the expression of Wnt target genes, such as AXIN2. LGK974 is potent and efficacious in multiple tumor models at well-tolerated doses in vivo, including murine and rat mechanistic breast cancer models driven by MMTV-Wnt1 and a human head and neck squamous cell carcinoma model (HN30). We also show that head and neck cancer cell lines with loss-of-function mutations in the Notch signaling pathway have a high response rate to LGK974. Together, these findings provide both a strategy and tools for targeting Wnt-driven cancers through the inhibition of PORCN.

https://www.pnas.org/content/pnas/110/50/20224.full.pdf

Targeting Wnt-driven cancer through the inhibition of Porcupine by LGK974

Purpose: The genetic differences between human papilloma virus (HPV)–positive and –negative head and neck squamous cell carcinomas (HNSCC) remain largely unknown To identify differential biology and novel therapeutic targets for both entities, we determined mutations and copy-number aberrations in a large cohort of locoregionally advanced HNSCC Experimental Design: We performed massively parallel sequencing of 617 cancer-associated genes in 120 matched tumor/normal samples (425% HPV-positive) Mutations and copy-number aberrations were determined and results validated with a secondary method Results: The overall mutational burden in HPV-negative and HPV-positive HNSCC was similar with an average of 152 versus 144 somatic exonic mutations in the targeted cancer-associated genes HPV-negative tumors showed a mutational spectrum concordant with published lung squamous cell carcinoma analyses with enrichment for mutations in TP53 , CDKN2A , MLL2 , CUL3 , NSD1 , PIK3CA , and NOTCH genes HPV-positive tumors showed unique mutations in DDX3X , FGFR2 / 3 and aberrations in PIK3CA , KRAS , MLL2 / 3 , and NOTCH1 were enriched in HPV-positive tumors Currently targetable genomic alterations were identified in FGFR1 , DDR2 , EGFR , FGFR2/3 , EPHA2 , and PIK3CA  EGFR , CCND1 , and FGFR1 amplifications occurred in HPV-negative tumors, whereas 176% of HPV-positive tumors harbored mutations in fibroblast growth factor receptor genes ( FGFR2 / 3 ), including six recurrent FGFR3 S249C mutations HPV-positive tumors showed a 58% incidence of KRAS mutations, and DNA-repair gene aberrations, including 78% BRCA1/2 mutations, were identified Conclusions: The mutational makeup of HPV-positive and HPV-negative HNSCC differs significantly, including targetable genes HNSCC harbors multiple therapeutically important genetic aberrations, including frequent aberrations in the FGFR and PI3K pathway genes Clin Cancer Res; 21(3); 632–41 ©2014 AACR  See related commentary by Krigsfeld and Chung, p 495

https://clincancerres.aacrjournals.org/content/clincanres/21/3/632.full.pdf

Integrative and comparative genomic analysis of HPV-positive and HPV-negative head and neck squamous cell carcinomas

Purpose: Aggressive cutaneous squamous cell carcinoma (cSCC) is often a disfiguring and lethal disease. Very little is currently known about the mutations that drive aggressive cSCC. Experimental Design: Whole-exome sequencing was performed on 39 cases of aggressive cSCC to identify driver genes and novel therapeutic targets. Significantly, mutated genes were identified with MutSig or complementary methods developed to specifically identify candidate tumor suppressors based upon their inactivating mutation bias. Results: Despite the very high-mutational background caused by UV exposure, 23 candidate drivers were identified, including the well-known cancer-associated genes TP53 , CDKN2A , NOTCH1 , AJUBA , HRAS , CASP8 , FAT1 , and KMT2C ( MLL3 ). Three novel candidate tumor suppressors with putative links to cancer or differentiation, NOTCH2 , PARD3 , and RASA1 , were also identified as possible drivers in cSCC. KMT2C mutations were associated with poor outcome and increased bone invasion. Conclusions: The mutational spectrum of cSCC is similar to that of head and neck squamous cell carcinoma and dominated by tumor-suppressor genes. These results improve the foundation for understanding this disease and should aid in identifying and treating aggressive cSCC. Clin Cancer Res; 20(24); 6582–92. ©2014 AACR .

https://clincancerres.aacrjournals.org/content/clincanres/20/24/6582.full.pdf

Mutational Landscape of Aggressive Cutaneous Squamous Cell Carcinoma

The Notch signalling pathway is evolutionarily conserved and is crucial for the development and homeostasis of most tissues. Deregulated Notch signalling leads to various diseases, such as T cell leukaemia, Alagille syndrome and a stroke and dementia syndrome known as CADASIL, and so strategies to therapeutically modulate Notch signalling are of interest. Clinical trials of Notch pathway inhibitors in patients with solid tumours have been reported, and several approaches are under preclinical evaluation. In this Review, we focus on aspects of the pathway that are amenable to therapeutic intervention, diseases that could be targeted and the various Notch pathway modulation strategies that are currently being explored.

Therapeutic modulation of Notch signalling — are we there yet?

From Fly Wings to Targeted Cancer Therapies: A Centennial for Notch Signaling

The survival of patients with oral squamous cell carcinoma (OSCC) has not changed significantly in several decades, leading clinicians and investigators to search for promising molecular targets. To this end, we performed comprehensive genomic analysis of gene expression, copy number, methylation and point mutations in OSCC. Integrated analysis revealed more somatic events than previously reported, identifying four major driver pathways (mitogenic signaling, Notch, cell cycle, TP53) and two additional key genes (FAT1, CASP8). The Notch pathway was defective in 66% of patients, and in follow-up studies of mechanism, functional NOTCH1 signaling inhibited proliferation of OSCC cell lines. Frequent mutation of CASP8 defines a new molecular subtype of OSCC with few copy number changes. Although genomic alterations are dominated by loss of tumor suppressor genes, 80% of patients harbored at least one genomic alteration in a targetable gene, suggesting that novel approaches to treatment may be possible for this debilitating disease.

https://cancerdiscovery.aacrjournals.org/content/candisc/3/7/770.full.pdf

Elsa Cortez

Papers

Integrative Genomic Characterization of Oral Squamous Cell Carcinoma Identifies Frequent Somatic Drivers