Tumors perturbing extracellular matrix biosynthesis. The case of von Recklinghausen's disease

The Importance of Being PI3K in the RAS Signaling Network

Ras proteins are essential mediators of a multitude of cellular processes, and its deregulation is frequently associated with cancer appearance, progression, and metastasis. Ras-driven cancers are usually aggressive and difficult to treat. Although the recent Food and Drug Administration (FDA) approval of the first Ras G12C inhibitor is an important milestone, only a small percentage of patients will benefit from it. A better understanding of the context in which Ras operates in different tumor types and the outcomes mediated by each effector pathway may help to identify additional strategies and targets to treat Ras-driven tumors. Evidence emerging in recent years suggests that both oncogenic Ras signaling in tumor cells and non-oncogenic Ras signaling in stromal cells play an essential role in cancer. PI3K is one of the main Ras effectors, regulating important cellular processes such as cell viability or resistance to therapy or angiogenesis upon oncogenic Ras activation. In this review, we will summarize recent advances in the understanding of Ras-dependent activation of PI3K both in physiological conditions and cancer, with a focus on how this signaling pathway contributes to the formation of a tumor stroma that promotes tumor cell proliferation, migration, and spread.

Metalloproteinase 1 downregulation in neurofibromatosis 1: Therapeutic potential of antimalarial hydroxychloroquine and chloroquine

Neurofibromatosis type 1 is an autosomal dominant genetic disorder caused by mutation in the neurofibromin 1 (NF1) gene. Its hallmarks are cutaneous findings including neurofibromas, benign peripheral nerve sheath tumors. We analyzed the collagen and matrix metalloproteinase 1 (MMP1) expression in Neurofibromatosis 1 cutaneous neurofibroma and found excessive expression of collagen and reduced expression of MMP1. To identify new therapeutic drugs for neurofibroma, we analyzed phosphorylation of components of the Ras pathway, which underlies NF1 regulation, and applied treatments to block this pathway (PD184352, U0126, and rapamycin) and lysosomal processes (chloroquine (CQ), hydroxychloroquine (HCQ), and bafilomycin A (BafA)) in cultured Neurofibromatosis 1 fibroblasts. We found that downregulation of the MMP1 protein was a key abnormal feature in the neurofibromatosis 1 fibroblasts and that the decreased MMP1 was restored by the lysosomal blockers CQ and HCQ, but not by the blockers of the Ras pathway. Moreover, the MMP1-upregulating activity of those lysosomal blockers was dependent on aryl hydrocarbon receptor (AHR) activation and ERK phosphorylation. Our findings suggest that lysosomal blockers are potential candidates for the treatment of Neurofibromatosis 1 neurofibroma.

Congenital cutaneous neurofibromas in neurofibromatosis type 1: Clinicopathological features in early infancy

BACKGROUND AND OBJECTIVE

Clinicopathological features of cutaneous neurofibromas presenting as large irregularly shaped congenital café-au-lait macules (CALM) in Neurofibromatosis type 1 (NF1) patients have not been well characterized. We aimed to analyze the histopathological findings of large "atypical" CALM in children with NF1.

PATIENTS AND METHODS

In this retrospective observational study we analyzed histopathological and immunostaining features of 21 biopsy specimens from 18 large hyperpigmented macules with irregular borders with or without hypertrichosis present during the first months of life in NF1 diagnosed children.

RESULTS

Of the 21 biopsies, ten showed a diffuse neurofibroma pattern and four exhibited characteristics of plexiform neurofibroma (PNF). In twelve specimens we observed groups of fusiform cells arranged linearly mimicking a small caliber nerve trunk with abnormal morphology. Repeated biopsies from two of these lesions performed at different ages showed transformation to a plexiform pattern. An increased interstitial cellularity was observed in 17 samples that was more evident around eccrine glands in 16 or accompanying hair follicles and vascular structures in twelve samples. All these cells had immunoreactivity for S100-protein, CD68 and were Melan-A positive in 15 samples.

CONCLUSION

Clinicopathological findings of congenital cutaneous neurofibromas provide early diagnostic clues of NF1 with high relevance for monitoring of these patients.

KRAS Oncogenic Signaling Extends beyond Cancer Cells to Orchestrate the Microenvironment

KRAS is one of the most frequently mutated oncogenes in cancer, being a potent initiator of tumorigenesis, a strong inductor of malignancy, and a predictive biomarker of response to therapy. Despite the large investment to understand the effects of KRAS activation in cancer cells, pharmacologic targeting of KRAS or its downstream effectors has not yet been successful at the clinical level. Recent studies are now describing new mechanisms of KRAS-induced tumorigenesis by analyzing its effects on the components of the tumor microenvironment. These studies revealed that the activation of KRAS on cancer cells extends to the surrounding microenvironment, affecting the properties and functions of its constituents. Herein, we discuss the most emergent perspectives on the relationship between KRAS-mutant cancer cells and their microenvironment components. Cancer Res; 78(1); 7-14. ©2017 AACR.