The interest in pancreatic stellate cells (PSCs) has been steadily growing over the past two decades due mainly to the central role these cells have in the desmoplastic reaction associated with diseases of the pancreas, such as pancreatitis or pancreatic cancer. In recent years, the scientific community has devoted substantial efforts to understanding the signaling pathways that govern PSC activation and interactions with neoplastic cells. This mini review aims to summarize some very recent findings on signaling in PSCs and highlight their impact to the field.

YAP, acting as a crucial transcription factor in nucleus, regulates the organ size, tissue homeostasis and tumorigenesis. Dysregulation of Hippo-YAP pathway brings a significant impact on the occurrence and development of various tumor types. Moreover, regulation of YAP/TAZ far exceeds the core kinase of the Hippo pathway, and gradually opens up new therapeutic targets. For the moment, chemotherapy together with radiotherapy act as routine methods to prolong the lives of cancer patients. Seeking more effective anti-neoplastic agents seems to be the urgent problem. This brief review focuses on the research progress of YAP inhibitors as the antineoplastic targets. Small molecule inhibitors or drugs have been discovered including verteporfin, dasatinib, statins, A35, JQ1, norcantharidin, agave, MLN8237, dobutamine and peptide-based YAP inhibitors. We are trying to seek novel therapies from the relationship between known drugs and potential mechanisms.

The Hippo signaling pathway is an evolutionarily conserved developmental network vital for the regulation of organ size, tissue homeostasis, repair and regeneration, and cell fate. The Hippo pathway has also been shown to have tumor suppressor properties. Hippo transduction involves a series of kinases and scaffolding proteins that are intricately connected to proteins in developmental cascades and in the tissue microenvironment. This network governs the downstream Hippo transcriptional co-activators, YAP and TAZ, which bind to and activate the output of TEADs, as well as other transcription factors responsible for cellular proliferation, self-renewal, differentiation, and survival. Surprisingly, there are few oncogenic mutations within the core components of the Hippo pathway. Instead, dysregulated Hippo signaling is a versatile accomplice to commonly mutated cancer pathways. For example, YAP and TAZ can be activated by oncogenic signaling from other pathways, or serve as co-activators for classical oncogenes. Emerging evidence suggests that Hippo signaling couples cell density and cytoskeletal structural changes to morphogenic signals and conveys a mesenchymal phenotype. While much of Hippo biology has been described in epithelial cell systems, it is clear that dysregulated Hippo signaling also contributes to malignancies of mesenchymal origin. This review will summarize the known molecular alterations within the Hippo pathway in sarcomas and highlight how several pharmacologic compounds have shown activity in modulating Hippo components, providing proof-of-principle that Hippo signaling may be harnessed for therapeutic application in sarcomas.