PHLDA1 Mediates Drug Resistance in Receptor Tyrosine Kinase-Driven Cancer.

Development of resistance causes failure of drugs targeting receptor tyrosine kinase (RTK) networks and represents a critical challenge for precision medicine. Here, we show that PHLDA1 downregulation is critical to acquisition and maintenance of drug resistance in RTK-driven cancer. Using fibroblast growth factor receptor (FGFR) inhibition in endometrial cancer cells, we identify an Akt-driven compensatory mechanism underpinned by downregulation of PHLDA1. We demonstrate broad clinical relevance of our findings, showing that PHLDA1 downregulation also occurs in response to RTK-targeted therapy in breast and renal cancer patients, as well as following trastuzumab treatment in HER2+ breast cancer cells. Crucially, knockdown of PHLDA1 alone was sufficient to confer de novo resistance to RTK inhibitors and induction of PHLDA1 expression re-sensitized drug-resistant cancer cells to targeted therapies, identifying PHLDA1 as a biomarker for drug response and highlighting the potential of PHLDA1 reactivation as a means of circumventing drug resistance.

Dysregulated FGF signalling in neoplastic disorders.

The fibroblast growth factor (FGF) signalling pathway contributes to the regulation of a multitude of cellular functions, impacting on proliferation, survival, differentiation and migration. This biological importance is reflected by its prominent role in carcinogenesis; often being hijacked by cancer cells to offer growth or survival advantage. FGF signalling can contribute a driving force in the malignancy of different cancer types; through alterations in ligands, receptors or regulatory molecules. The dramatic advances in genomics technologies have highlighted how mutation, amplification, translocation or loss of elements in the FGF signalling network can contribute to cancer. Added to this are the stromal influences of FGF signalling. Dissection of the mechanisms that underlie the pro-tumourigenic effects resulting from perturbations to the FGF signalling network will be of utmost importance to the development of therapeutic approaches to treat FGF receptor (FGFR)-driven cancers. In this review, we will focus on the mechanisms of FGF deregulation, the prevalence of aberrations in different cancer types, and how we are progressing in the development of targeted therapies.

Nrf2 Activation Promotes Keratinocyte Survival during Early Skin Carcinogenesis via Metabolic Alterations.

Pharmacologic activation of the transcription factor NRF2 has been suggested to offer a strategy for cancer prevention. In this study, we present evidence from murine tumorigenesis experiments suggesting there may be limitations to this possibility, based on tumorigenic effects of Nrf2 in murine keratinocytes that have not been described previously. In this setting, Nrf2 expression conferred metabolic alterations in keratinocytes that were protumorigenic in nature, affecting enzymes involved in glutathione biosynthesis or in the oxidative pentose phosphate pathway and other NADPH-producing enzymes. Under stress conditions, coordinate increases in NADPH, purine, and glutathione levels promoted the survival of keratinocytes harboring oncogenic mutations, thereby promoting tumor development. The protumorigenic activity of Nrf2 in keratinocytes was particularly significant in a mouse model of skin tumorigenesis that did not rely upon chemical carcinogenesis. In exploring the clinical relevance of our findings, we confirm that NRF2 and protumorigenic NRF2 target genes were activated in some actinic keratoses, the major precancerous lesion in human skin. Overall, our results reveal an unexpected tumor-promoting activity of activated NRF2 during early phases of skin tumorigenesis.