Mimicking Tumor Cell Heterogeneity of Colorectal Cancer in a Patient-derived Organoid-Fibroblast Model.

BACKGROUND & AIMS: Patient-derived organoid cancer models are generated from epithelial tumor cells and reflect tumor characteristics. However, they lack the complexity of the tumor microenvironment, which is a key driver of tumorigenesis and therapy response. Here, we developed a colorectal cancer organoid model that incorporates matched epithelial cells and stromal fibroblasts. METHODS: Primary fibroblasts and tumor cells were isolated from colorectal cancer specimens. Fibroblasts were characterized for their proteome, secretome, and gene expression signatures. Fibroblast/organoid co-cultures were analyzed by immunohistochemistry and compared with their tissue of origin, as well as on gene expression levels compared with standard organoid models. Bioinformatics deconvolution was used to calculate cellular proportions of cell subsets in organoids based on single-cell RNA sequencing data. RESULTS: Normal primary fibroblasts, isolated from tumor adjacent tissue, and cancer associated fibroblasts retained their molecular characteristics in vitro, including higher motility of cancer associated compared with normal fibroblasts. Importantly, both cancer-associated fibroblasts and normal fibroblasts supported cancer cell proliferation in 3D co-cultures, without the addition of classical niche factors. Organoids grown together with fibroblasts displayed a larger cellular heterogeneity of tumor cells compared with mono-cultures and closely resembled the in vivo tumor morphology. Additionally, we observed a mutual crosstalk between tumor cells and fibroblasts in the co-cultures. This was manifested by considerably deregulated pathways such as cell-cell communication and extracellular matrix remodeling in the organoids. Thrombospondin-1 was identified as a critical factor for fibroblast invasiveness. CONCLUSION: We developed a physiological tumor/stroma model, which will be vital as a personalized tumor model to study disease mechanisms and therapy response in colorectal cancer.

Selective Eradication of Colon Cancer Cells Harboring PI3K and/or MAPK Pathway Mutations in 3D Culture by Combined PI3K/AKT/mTOR Pathway and MEK Inhibition.

Colorectal cancer (CRC) is the second deadliest cancer in the world. Besides APC and p53 alterations, the PI3K/AKT/MTOR and MAPK pathway are most commonly mutated in CRC. So far, no treatment options targeting these pathways are available in routine clinics for CRC patients. We systematically analyzed the response of CRC cells to the combination of small molecular inhibitors targeting the PI3K and MAPK pathways. We used CRC cells in 2D, 3D spheroid, collagen gel cultures and freshly isolated organoids for drug response studies. Readout for drug response was spheroid or organoid growth, spheroid outgrowth, metabolic activity, Western blotting and immunofluorescence. We found profound tumor cell destruction under treatment with a combination of Torin 1 (inhibiting mTOR), MK2206 (targeting AKT) and selumetinib (inhibiting MEK) in 3D but not in 2D. Induction of cell death was due to apoptosis. Western blot analysis revealed efficient drug action. Gedatolisib, a dual PI3K/mTOR inhibitor, could replace Torin1/MK2206 with similar efficiency. The presence of PI3K and/or RAS-RAF-MAPK pathway mutations accounted for treatment responsiveness. Here, we identified a novel, efficient therapy, which induced proliferation stop and tumor cell destruction in vitro based on the genetic background. These preclinical findings show promise to further test this combi-treatment in vivo in mice and to potentially develop a mutation specific targeted therapy for CRC patients.

Identification of Rigosertib for the Treatment of Recessive Dystrophic Epidermolysis Bullosa-Associated Squamous Cell Carcinoma.

PURPOSE: Squamous cell carcinoma (SCC) of the skin is the leading cause of death in patients with the severe generalized form of the genetic disease recessive dystrophic epidermolysis bullosa (RDEB). Although emerging data are identifying why patients suffer this fatal complication, therapies for treatment of RDEB SCC are in urgent need.Experimental Design: We previously identified polo-like kinase 1 (PLK1) as a therapeutic target in skin SCC, including RDEB SCC. Here, we undertake a screen of 6 compounds originally designated as PLK1 inhibitors, and detail the efficacy of the lead compound, the multipathway allosteric inhibitor ON-01910, for targeting RDEB SCC in vitro and in vivo. RESULTS: ON-01910 (or rigosertib) exhibited significant specificity for RDEB SCC: in culture rigosertib induced apoptosis in 10 of 10 RDEB SCC keratinocyte populations while only slowing the growth of normal primary skin cells at doses 2 orders of magnitude higher. Furthermore, rigosertib significantly inhibited the growth of two RDEB SCC in murine xenograft studies with no apparent toxicity. Mechanistically, rigosertib has been shown to inhibit multiple signaling pathways. Comparison of PLK1 siRNA with MEK inhibition, AKT inhibition, and the microtubule-disrupting agent vinblastine in RDEB SCC shows that only PLK1 reduction exhibits a similar sensitivity profile to rigosertib. CONCLUSIONS: These data support a "first in RDEB" phase II clinical trial of rigosertib to assess tumor targeting in patients with late stage, metastatic, and/or unresectable SCC.

Thrombospondin-1 Is a Major Activator of TGF-ß Signaling in Recessive Dystrophic Epidermolysis Bullosa Fibroblasts.

Mutations in the gene encoding collagen VII cause the devastating blistering disease recessive dystrophic epidermolysis bullosa (RDEB). RDEB is characterized by severe skin fragility and nonhealing wounds aggravated by scarring and fibrosis. We previously showed that TSP1 is increased in RDEB fibroblasts. Because transforming growth factor-ß (TGF-ß) signaling is also increased in RDEB, and TSP1 is known to activate TGF-ß, we investigated the role of TSP1 in TGF-ß signaling in RDEB patient cells. Knockdown of TSP1 reduced phosphorylation of smad3 (a downstream target of TGF-ß signaling) in RDEB primary fibroblasts, whereas overexpression of collagen VII reduced phosphorylation of smad3. Furthermore, inhibition of TSP1 binding to the LAP/TGF-ß complex decreased fibrosis in engineered extracellular matrix formed by RDEB fibroblasts, as evaluated by picrosirius red staining and analyses of birefringent collagen fibrillar deposits. We show that collagen VII binds TSP1, which could potentially limit TSP1-LAP association and subsequent TGF-ß activation. Our study suggests a previously unreported mechanism for increased TGF-ß signaling in the absence of collagen VII in RDEB patient skin. Moreover, these data identify TSP1 as a possible target for reducing fibrosis in the tumor-promoting dermal microenvironment of RDEB patients.

Precision Medicine for Heritable Skin Diseases-The Paradigm of Epidermolysis Bullosa.

The 2016 JID Beijing Workshop, held in the context of the 5th National Congress of Investigative Dermatology of the Chinese Society of Dermatology, had the thematic focus on "Precision Medicine in Dermatology." This theme was extremely timely, yet forward-looking, due to the fact that precision medicine is one of the fastest growing paradigms of contemporary medicine (Box 1).

APOBEC mutation drives early-onset squamous cell carcinomas in recessive dystrophic epidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare inherited skin and mucous membrane fragility disorder complicated by early-onset, highly malignant cutaneous squamous cell carcinomas (SCCs). The molecular etiology of RDEB SCC, which arises at sites of sustained tissue damage, is unknown. We performed detailed molecular analysis using whole-exome, whole-genome, and RNA sequencing of 27 RDEB SCC tumors, including multiple tumors from the same patient and multiple regions from five individual tumors. We report that driver mutations were shared with spontaneous, ultraviolet (UV) light-induced cutaneous SCC (UV SCC) and head and neck SCC (HNSCC) and did not explain the early presentation or aggressive nature of RDEB SCC. Instead, endogenous mutation processes associated with apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) deaminases dominated RDEB SCC. APOBEC mutation signatures were enhanced throughout RDEB SCC tumor evolution, relative to spontaneous UV SCC and HNSCC mutation profiles. Sixty-seven percent of RDEB SCC driver mutations was found to emerge as a result of APOBEC and other endogenous mutational processes previously associated with age, potentially explaining a >1000-fold increased incidence and the early onset of these SCCs. Human papillomavirus-negative basal and mesenchymal subtypes of HNSCC harbored enhanced APOBEC mutational signatures and transcriptomes similar to those of RDEB SCC, suggesting that APOBEC deaminases drive other subtypes of SCC. Collectively, these data establish specific mutagenic mechanisms associated with chronic tissue damage. Our findings reveal a cause for cancers arising at sites of persistent inflammation and identify potential therapeutic avenues to treat RDEB SCC.

Amlexanox Enhances Premature Termination Codon Read-Through in COL7A1 and Expression of Full Length Type VII Collagen: Potential Therapy for Recessive Dystrophic Epidermolysis Bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare monogenic blistering disorder caused by the lack of functional type VII collagen, leading to skin fragility and subsequent trauma-induced separation of the epidermis from the underlying dermis. A total of 46% of patients with RDEB harbor at least one premature termination codon (PTC) mutation in COL7A1, and previous studies have shown that aminoglycosides are able to overcome RDEB PTC mutations by inducing "read-through" and incorporation of an amino acid at the PTC site. However, aminoglycoside toxicity will likely prevent widespread clinical application. Here the FDA-approved drug amlexanox was tested for its ability to read-through PTC mutations in cells derived from patients with RDEB. Eight of 12 different PTC alleles responded to treatment and produced full length protein, in some cases more than 50% relative to normal controls. Read-through type VII collagen was readily detectable in cell culture media and also localized to the dermal-epidermal junction in organotypic skin culture. Amlexanox increased COL7A1 transcript and the phosphorylation of UPF-1, an RNA helicase associated with nonsense-mediated mRNA decay, suggesting that amlexanox inhibits nonsense-mediated mRNA decay in cells from patients with RDEB that respond to read-through treatment. This preclinical study demonstrates the potential of repurposing amlexanox for the treatment of patients with RDEB harboring PTC mutation in COL7A1.