The survival rate for patients with head and neck cancer (HNC) diagnosed with cervical lymph node (cLN) or distant metastasis is low. Genomic alterations in the HRAS oncogene are associated with advanced tumor stage and metastasis in HNC. Elucidation of the molecular mechanisms by which mutated HRAS (HRASmut) facilitates HNC metastasis could lead to improved treatment options for patients. Here, we examined metastasis driven by mutant HRAS in vitro and in vivo using HRASmut human HNC cell lines, patient-derived xenografts, and a novel HRASmut syngeneic model. Genetic and pharmacological manipulations indicated that HRASmut was sufficient to drive invasion in vitro and metastasis in vivo. Targeted proteomic analysis showed that HRASmut promoted AXL expression via suppressing the Hippo pathway and stabilizing YAP1 activity. Pharmacological blockade of HRAS signaling with the farnesyltransferase inhibitor tipifarnib activated the Hippo pathway and reduced the nuclear export of YAP1, thus suppressing YAP1-mediated AXL expression and metastasis. AXL was required for HRASmut cells to migrate and invade in vitro and to form regional cLN and lung metastases in vivo. In addition, AXL-depleted HRASmut tumors displayed reduced lymphatic and vascular angiogenesis in the primary tumor. Tipifarnib treatment also regulated AXL expression and attenuated VEGFA and VEGFC expression, thus regulating tumor-induced vascular formation and metastasis. Our results indicate that YAP1 and AXL are crucial factors for HRASmut-induced metastasis and that tipifarnib treatment can limit the metastasis of HNC tumors with HRAS mutations by enhancing YAP1 cytoplasmic sequestration and downregulating AXL expression. Significance: Mutant HRAS drives metastasis of head and neck cancer by switching off the Hippo pathway to activate the YAP1–AXL axis and to stimulate lymphovascular angiogenesis.

Objectives: To investigate the clinical characteristics and pre-biopsy provisional diagnoses of benign oral mucosal tumors. Material and Methods: A 10- year retrospective analysis of all benign tumors of the oral mucosa, from a university- affiliated oral and maxillofacial surgery department. Results: 146 benign tumors were included. The mean age was 49.6 years, with an approximately equal gender distribution. The most prevalent tumor types were lipomatous tumors (27.4%), vascular (23.3%), and salivary gland tumors (16.5%). Tongue, labial and buccal mucosa were the most frequently involved sites. The vast majority (98.6%) presented as non-ulcerated masses. Only 2 (1.4%) presented as ulcerated masses. The clinical provisional diagnosis correctly classified lesions as non-malignant in 93.3%. In only 9 (6.7%) suspicion of malignancy was included in the provisional diagnosis. However, benign neoplasia was unsuspected in 42.1% of tumors. These cases were clinically classified as reactive. Conclusions: Benign tumors were most likely to be clinically correctly classified as non-malignant, but even in the setting of experienced oral surgeons, neoplasia was unsuspected in more than 40% of cases. This data strongly supports the need to biopsy every oral mucosal mass, since inaccurate clinical evaluation of the lesion’s biological nature was a frequent event.