Notch-signaling and nonmelanoma skin cancer: an ancient friend, revisited

Effects of β-HPV on DNA damage response pathways to drive carcinogenesis: a review

The DDR is a complex signaling network responsible for the preservation of genomic integrity. Beta human papillomaviruses (β-HPVs) are able to destabilize the host genome by attenuating the DDR machinery at the molecular scale following expression of the oncogenes E6 and E7. In the event of β-HPV infection, the E6- and E7-mediated inhibition of the DDR enhances the oncogenicity of UV-induced mutations to enable carcinogenesis in an otherwise immunocompetent host, marking an important mechanistic divergence from the alpha genus of HPVs. In this review, we summarize recent updates to build upon the 'hit-and-run' hypothesis of β-HPV pathomechanism and highlight strain-dependent variations. Simultaneously, we illuminate points within the β-HPV-DDR interface that may unravel new insights for HPV viral genetics, genus-specific mechanistic models, and developments in targeted molecular therapy of β-HPV-related cancers.

The Impact of Notch Signaling for Carcinogenesis and Progression of Nonmelanoma Skin Cancer: Lessons Learned from Cancer Stem Cells, Tumor Angiogenesis, and Beyond

Since many decades, nonmelanoma skin cancer (NMSCs) is the most common malignancy worldwide. Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) are the major types of NMSCs, representing approximately 70% and 25% of these neoplasias, respectively. Because of their continuously rising incidence rates, NMSCs represent a constantly increasing global challenge for healthcare, although they are in most cases nonlethal and curable (e.g., by surgery). While at present, carcinogenesis of NMSC is still not fully understood, the relevance of genetic and molecular alterations in several pathways, including evolutionary highly conserved Notch signaling, has now been shown convincingly. The Notch pathway, which was first developed during evolution in metazoans and that was first discovered in fruit flies (Drosophila melanogaster), governs cell fate decisions and many other fundamental processes that are of high relevance not only for embryonic development, but also for initiation, promotion, and progression of cancer. Choosing NMSC as a model, we give in this review a brief overview on the interaction of Notch signaling with important oncogenic and tumor suppressor pathways and on its role for several hallmarks of carcinogenesis and cancer progression, including the regulation of cancer stem cells, tumor angiogenesis, and senescence.

The genomic landscape of metastatic breast cancer: Insights from 11,000 tumors

BACKGROUND

Metastatic breast cancer is the leading cause of cancer death in women, but the genomics of metastasis in breast cancer are poorly studied.

METHODS

We explored a set of 11,616 breast tumors, including 5,034 metastases, which had undergone targeted sequencing during standard clinical care.

RESULTS

Besides the known hotspot mutations in ESR1, we observed a metastatic enrichment of previously unreported, lower-prevalence mutations in the ligand-binding domain, implying that these mutations may also be functional. Furthermore, individual ESR1 hotspots are significantly enriched in specific metastatic tissues and histologies, suggesting functional differences between these mutations. Other alterations enriched across all metastases include loss of function of the CDK4 regulator CDKN1B, and mutations in the transcription factor CTCF. Mutations enriched at specific metastatic sites generally reflect biology of the target tissue and may be adaptations to growth in the local environment. These include PTEN and ASXL1 alterations in brain metastases and NOTCH1 alterations in skin. We observed an enrichment of KRAS, KEAP1, STK11 and EGFR mutations in lung metastases. However, the patterns of other mutations in these tumors indicate that these are misdiagnosed lung primaries rather than breast metastases.

CONCLUSIONS

An order-of-magnitude increase in samples relative to previous studies allowed us to detect novel genomic characteristics of metastatic cancer and to expand and clarify previous findings.

Analysis of clinically relevant somatic mutations in high-risk head and neck cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma is the second most prevalent malignancy, most frequently occurring in the head and neck (head and neck cutaneous squamous cell carcinoma). Treatment of locally advanced or metastatic disease is associated with functional morbidity and disfigurement. Underlying genetic mechanisms are poorly understood. Targeted sequencing of 48 clinically relevant genes was performed on DNA extracted from formalin-fixed and paraffin-embedded high-risk primary head and neck cutaneous squamous cell carcinomas that remained non-metastatic at minimum follow-up of 24 months. Associations of somatic mutations with clinicopathologic characteristics were evaluated and compared with those described in the literature for metastatic disease. Alterations in 44 cancer-associated genes were identified. TP53 was mutated in 100% of cases; APC, ATM, ERBB4, GNAQ, KIT, RB1 and ABL1 were altered in 60% of cases. FGFR2 mutations (40%) were exclusively seen in patients with perineural invasion. MLH1 mutations were exclusively seen in the two younger patients (<45 years). Lower incidences of NOTCH1 mutations were observed compared with that described in metastatic head and neck cutaneous squamous cell carcinoma in the literature. Somatic mutations susceptible to EGFR inhibitors, and other small molecular targeted therapeutics were seen in 60% of cases. This study provides insights into somatic mutations in non-metastatic, high-risk head and neck cutaneous squamous cell carcinoma and identifies potential therapeutic targets. Alterations in FGFR2 and NOTCH1 may have roles in local and distant disease progression.

Loss of Genome Fidelity: Beta HPVs and the DNA Damage Response

While the role of genus alpha human papillomaviruses in the tumorigenesis and tumor maintenance of anogenital and oropharyngeal cancers is well-established, the role of genus beta human papilloviruses (β-HPVs) in non-melanoma skin cancers (NMSCs) is less certain. Persistent β-HPV infections cause NMSCs in sun-exposed skin of people with a rare genetic disorder, epidermodysplasia verruciformis. However, β-HPV infections in people without epidermodysplasia verruciformis are typically transient. Further, β-HPV gene expression is not necessary for tumor maintenance in the general population as on average there is fewer than one copy of the β-HPV genome per cell in NMSC tumor biopsies. Cell culture, epidemiological, and mouse model experiments support a role for β-HPV infections in the initiation of NMSCs through a "hit and run" mechanism. The virus is hypothesized to act as a cofactor, augmenting the genome destabilizing effects of UV. Supporting this idea, two β-HPV proteins (β-HPV E6 and E7) disrupt the cellular response to UV exposure and other genome destabilizing events by abrogating DNA repair and deregulating cell cycle progression. The aberrant damage response increases the likelihood of oncogenic mutations capable of driving tumorigenesis independent of a sustained β-HPV infection or continued viral protein expression. This review summarizes what is currently known about the deleterious effects of β-HPV on genome maintenance in the context of the virus's putative role in NMSC initiation.

The role and therapeutic targeting of α-, β- and γ-secretase in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in the elderly and its prevalence is set to increase rapidly in coming decades. However, there are as yet no available drugs that can halt or even stabilize disease progression. One of the main pathological features of AD is the presence in the brain of senile plaques mainly composed of aggregated β amyloid (Aβ), a derivative of the longer amyloid precursor protein (APP). The amyloid hypothesis proposes that the accumulation of Aβ within neural tissue is the initial event that triggers the disease. Here we review research efforts that have attempted to inhibit the generation of the Aβ peptide through modulation of the activity of the proteolytic secretases that act on APP and discuss whether this is a viable therapeutic strategy for treating AD.

Evaluation of 122 advanced-stage cutaneous squamous cell carcinomas by comprehensive genomic profiling opens the door for new routes to targeted therapies

BACKGROUND

The authors hypothesized that comprehensive genomic profiling of advanced-stage cutaneous squamous cell carcinoma (cSCC) could identify genomic-derived drug targets of therapy for patients with conventional therapy-resistant disease.

METHODS

Comprehensive genomic profiling of 315 cancer genes was applied to 50 ng of DNA from 122 cSCC cases for the evaluation of all classes of genomic alterations (GAs). Clinically relevant genomic alterations (CRGAs) were defined as those identifying anticancer drugs on the market or in registered clinical trials.

RESULTS

There were 21 women (17%) and 101 men (83%) with a median age of 64.9 years (range, 21-87 years). Eleven cSCC cases (9%) were histologic AJCC grade 1, 69 (57%) were grade 2, and 42 (34%) were grade 3. The primary cSCC was used for sequencing in 77 cases (63%). Metastatic lesions were sequenced in 37% of cases. There were 1120 total GAs identified (average of 9.2 GAs per tumor), with 100% of cases harboring at least 1 alteration. Of the 122 cSCCs, 107 (88%) harbored at least 1 CRGA (2.5 CRGAs per cSCC) includingNOTCH1 (43%); patched 1 (PTCH1) (11%); BRCA2 (10%); HRAS (8%); ataxia telangiectasia mutated (ATM) (7%); erb-B2 receptor tyrosine kinase 4 (ERBB4) (7%); neurofibromatosis type 1 (NF1) (7%); erb-B2 receptor tyrosine kinase 2 (ERBB2) (6%); phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) (6%); cyclin D1 (CCND1) (6%); epidermal growth factor receptor (EGFR) (5%); and F-box and WD repeat domain containing 7, E3 ubiquitin protein ligase (FBXW7) (5%).

CONCLUSIONS

In the current study, approximately 88% of patients with cSCC were found to harbor clinically relevant GAs that have the potential to guide the treatment of patients with advanced-stage tumors with targeted therapeutic agents. Cancer 2016;122:249-257. © 2015 American Cancer Society.

Inhibition of the Jagged/Notch pathway inhibits retinoblastoma cell proliferation via suppressing the PI3K/Akt, Src, p38MAPK and Wnt/β‑catenin signaling pathways

The Notch signaling pathway is a highly conserved developmental pathway, which is important in the regulation of cellular proliferation, differentiation and apoptosis. The aberrant expression of the Notch pathway has been associated with carcinogenesis in various types of cancer. In order to investigate the expression profiles and biological functions of Notch receptors and ligands in retinoblastoma, the expression levels of their proteins in the human retinoblastoma cell line SO‑Rb50 using western blot analysis was assessed. The present study revealed that Notch1 and Jagged2 were highly expressed compared with human retinal pigment epithelial cells. When treated with DAPT, a specific inhibitor of Notch receptor cleavage, expression of Notch1 and Jagged2 were downregulated in a dose‑dependent manner, which was accompanied by substantial cell growth arrest, as indicated by the Cell Counting kit‑8 assay. In addition, phosphorylation of Akt, p38 mitogen‑activated protein kinase and Src, together with the expression of phosphoinositide 3‑kinase and β‑catenin, was abated in a dose‑dependent manner. However, expression of either total extracellular signal‑regulated kinase (Erk)1/2 or phospho‑Erk1/2 was not changed in SO‑Rb50 cells. These findings demonstrated that the Jagged2/Notch1 pathway can promote oncogenesis in retinoblastoma in co‑operation with multiple signaling pathways. The inhibition of the Notch signaling pathway by DAPT represents a potentially attractive strategy for the therapy of retinoblastoma.

The human papillomavirus type 8 E6 protein interferes with NOTCH activation during keratinocyte differentiation

Cutaneous β-human papillomavirus (β-HPV) E6 proteins inhibit NOTCH signaling by associating with the transcriptional coactivator MAML1. NOTCH has tumor suppressor activities in epithelial cells and is activated during keratinocyte differentiation. Here we report that HPV type 8 (HPV8) E6 subverts NOTCH activation during keratinocyte differentiation by inhibiting RBPJ/MAML1 transcriptional activator complexes at NOTCH target DNA. NOTCH inhibition impairs epithelial differentiation and may thus contribute to β-HPV replication and viral oncogenesis.

No evidence for induction of key components of the Notch signaling pathway (Notch-1, Jagged-1) by treatment with UV-B, 1,25(OH)(2)D(3), and/or epigenetic drugs (TSA, 5-Aza) in human keratinocytes in vitro

Notch signaling is of high importance for growth and survival of various cell types. We now analyzed the protein expression of two key components of the Notch signaling pathway (Notch-1, Jagged-1) in spontaneously immortalized (HaCaT) and in malignant (SCL-1) human keratinocytes, using western analysis. We found that Notch-1 and its corresponding ligand Jagged-1 are expressed in both cell lines, with no marked change following UV-B treatment. Moreover, treatment of both cell lines before or after UV-B irradiation with 1,25-dihydroxyvitamin D₃, the biologically active form of vitamin D, and/or epigenetic modulating drugs (TSA; 5-Aza) did not result in a marked modulation of the protein expression of Notch-1 or Jagged-1. Under the experimental conditions of this study, treatment with 1,25(OH)₂D₃ protected human keratinocytes in part against the antiproliferative effects of UV-B-radiation. In conclusion, our findings do not point at a differential expression of these two key components of Notch signaling in non-malignant as compared to malignant human keratinocytes, indicating that alterations in their expression are not of importance for the photocarcinogenesis of human squamous cell carcinomas. Moreover, our findings do not support the hypothesis that modulation of Notch signaling may be involved in the photoprotective effect of 1,25-dihydroxyvitamin D₃, that we and others reported previously. Additionally, we demonstrate that epigenetic modulating drugs (TSA, 5-Aza) do not markedly modulate the expression Notch-1 or Jagged-1 in UV-B-treated human keratinocytes in vitro.