Cutaneous squamous cell carcinoma (cuSCC) comprises 15–20% of all skin cancers, accounting for over 700,000 cases in USA annually. Most cuSCC arise in association with a distinct precancerous lesion, the actinic keratosis (AK). To identify potential targets for molecularly targeted chemoprevention, here we perform integrated cross-species genomic analysis of cuSCC development through the preneoplastic AK stage using matched human samples and a solar ultraviolet radiation-driven Hairless mouse model. We identify the major transcriptional drivers of this progression sequence, showing that the key genomic changes in cuSCC development occur in the normal skin to AK transition. Our data validate the use of this ultraviolet radiation-driven mouse cuSCC model for cross-species analysis and demonstrate that cuSCC bears deep molecular similarities to multiple carcinogen-driven SCCs from diverse sites, suggesting that cuSCC may serve as an effective, accessible model for multiple SCC types and that common treatment and prevention strategies may be feasible.

Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies.DOI: http://dx.doi.org/10.7554/eLife.00969.001

BRAF inhibitor (BRAFi) therapy is associated with the induction of neoplasia, most commonly cutaneous squamous cell carcinoma (cuSCC). This toxicity is explained in part by “paradoxical ERK activation,” or the hyperactivation of ERK signaling by BRAFi in BRAF wild-type cells. However, the rate of cuSCC induction varies widely among BRAFi. To explore this mechanistically, we profiled paradoxical ERK activation by vemurafenib, dabrafenib, encorafenib (LGX818), and PLX8394, demonstrating that vemurafenib induces ERK activation the greatest, while dabrafenib and encorafenib have higher “paradox indices”, defined as the pERK activation EC80 divided by the IC80 against A375, corresponding to wider therapeutic windows for achieving tumor inhibition without paradoxical ERK activation. Our results identify differences in the paradox indices of these compounds as a potential mechanism for the differences in cuSCC induction rates and highlight the utility of using ERK activity as a biomarker for maximizing the clinical utility of BRAFi.

BackgroundVasoplegia is associated with adverse outcomes following cardiac surgery; however, its impact following left ventricular assist device implantation is largely unexplored.Methods and ResultsIn 252 consecutive patients receiving a left ventricular assist device, vasoplegia was defined as the occurrence of normal cardiac function and index but with the need for intravenous vasopressors within 48 hours following surgery for >24 hours to maintain a mean arterial pressure >70 mm Hg. We further categorized vasoplegia as none; mild, requiring 1 vasopressor (vasopressin, norepinephrine, or high‐dose epinephrine [>5 μg/min]); or moderate to severe, requiring ≥2 vasopressors. Predictors of vasoplegia severity were determined using a cumulative logit (ordinal logistic regression) model, and 1‐year mortality was evaluated using competing‐risks survival analysis. In total, 67 (26.6%) patients developed mild vasoplegia and 57 (22.6%) developed moderate to severe vasoplegia. The multivariable model for vasoplegia severity utilized preoperative Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile, central venous pressure, systolic blood pressure, and intraoperative cardiopulmonary bypass time, which yielded an area under the curve of 0.76. Although no significant differences were noted in stroke or pump thrombosis rates (P=0.87 and P=0.66, respectively), respiratory failure and major bleeding increased with vasoplegia severity (P<0.01). Those with moderate to severe vasoplegia had a significantly higher risk of mortality than those without vasoplegia (adjusted hazard ratio: 2.12; 95% confidence interval, 1.08–4.18; P=0.03).ConclusionsVasoplegia is predictive of unfavorable outcomes, including mortality. Risk factors for future research include preoperative INTERMACS profile, central venous pressure, systolic blood pressure, and intraoperative cardiopulmonary bypass time.

Sorafenib is FDA-approved for the treatment of renal cell carcinoma and hepatocellular carcinoma and has been combined with numerous other targeted therapies and chemotherapies in the treatment of many cancers. Unfortunately, as with other RAF inhibitors, patients treated with sorafenib have a 5–10% rate of developing cutaneous squamous cell carcinoma/keratoacanthomas. Paradoxical activation of ERK in BRAF-wild-type cells has been implicated in RAF-inhibitor-induced cSCC. Here we report that sorafenib suppresses UV-induced apoptosis specifically by inhibiting JNK activation through the off-target inhibition of ZAK kinase. Our results implicate suppression of JNK signaling, independent of the ERK pathway, as an additional mechanism of adverse effects of sorafenib. This has broad implications for combination therapies using sorafenib with other modalities that induce apoptosis.