Genomic alterations converging on persistent activation of the PI3K/mTOR pathway represent one of the most frequently altered signaling circuitries in cancer. However, the clinical efficacy of mTOR inhibitors (mTORi) has been limited. In this study, we took advantage of the widespread activation of PI3K/mTOR signaling in head and neck squamous cell carcinoma (HNSCC) and the promising effects of mTORi in HNSCC experimental models and recent clinical trials to gain a mechanistic understanding of the antitumoral activity of mTORi. A genome-wide CRISPR screen revealed that treatment with mTORi promotes the autophagic degradation of ferritin (ferritinophagy), consequently increasing free intracellular iron, inducing lipid peroxidation, and ultimately driving cancer cell demise by ferroptosis. These findings provide a rationale for synergistic combinations repurposing approved drugs that disable cellular ferroptotic defense mechanisms. Together, this study provides a molecular framework underlying the antitumor activity of mTORi in HNSCC, thereby revealing multimodal precision therapies for HNSCC and many human malignancies displaying overactive PI3K/mTOR signaling. Significance: Inhibition of mTOR induces ferritinophagy that increases free iron and stimulates ferroptosis, suggesting that this axis could be harnessed to help predict responses and to develop rational combination therapies to overcome resistance.

The comprehensive genomic analysis of the head and neck squamous cell carcinoma (HNSCC) oncogenome revealed the frequent loss of p16INK4A (CDKN2A) and amplification of cyclin D1 genes in most human papillomavirus–negative HNSCC lesions. However, cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors have shown modest effects in the clinic. The aberrant activation of the PI3K/mTOR pathway is highly prevalent in HNSCC, and recent clinical trials have shown promising clinical efficacy of mTOR inhibitors (mTORi) in the neoadjuvant and adjuvant settings but not in patients with advanced HNSCC. By implementing a kinome-wide CRISPR/Cas9 screen, we identified cell-cycle inhibition as a synthetic lethal target for mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergism in HNSCC-derived cells in vitro and in vivo. Remarkably, we found that an adaptive increase in cyclin E1 (CCNE1) expression upon palbociclib treatment underlies the rapid acquired resistance to this CDK4/6 inhibitor. Mechanistically, mTORi inhibits the formation of eIF4G–CCNE1 mRNA complexes, with the consequent reduction in mRNA translation and CCNE1 protein expression. Our findings suggest that mTORi reverts the adaptive resistance to palbociclib. This provides a multimodal therapeutic option for HNSCC by cotargeting mTOR and CDK4/6, which in turn may halt the emergence of palbociclib resistance. Significance: A kinome-wide CRISPR/Cas9 screen identified cell-cycle inhibition as a synthetic lethal target of mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergistic effects in HNSCC. Mechanistically, mTORis inhibited palbociclib-induced increase in CCNE1.

Although nasal septal abscesses are uncommon, their cosmetic complications can be severe. Hence, prompt diagnosis and treatment are important. Here, we report a case of aseptic nasal septal abscess in a patient with proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA)-positive ulcerative colitis (UC), in which phlebitis was observed and granulomatosis with polyangiitis (GPA) might co-exist. A 27-year-old female suffered from intermittent abdominal pain and diarrhea for several years. She visited our hospital complaining of worsening swelling and pain in the middle forehead and fever lasting 2 weeks. Physical examination and computed tomography revealed severe swelling of the nasal septum. The patient was diagnosed with nasal septal abscess, and incision drainage and biopsy from the bilateral nasal septum were performed, which showed severe ulcerative neutrophilic mucositis with phlebitis. Simultaneously, blood examination yielded slight positivity for PR3-ANCA. Colonoscopy, including biopsy, revealed severe inflammation without vasculitis nor granuloma, which led to the diagnosis with PR3-ANCA-positive UC. Phlebitis in the nasal mucosa and elevated PR3-ANCA suggested co-existing GPA; hence, she was treated with glucocorticoids and rituximab. Following treatment, the nasal septal abscess and digestive symptoms disappeared. She was discharged on day 25 without symptom recurrence or major nasal deformity. For the prevention of nasal deformity due to persistent inflammation, prompt administration of immunosuppressive therapy should be considered with adequate evaluations for systemic diseases, including UC and GPA.

Long non-coding RNAs (lncRNAs) have emerged as a significant player in various cancers, including pancreatic cancer. However, how lncRNAs are aberrantly expressed in cancers is largely unknown. We hypothesized that lncRNAs would be regulated by signaling pathways and contribute to malignant phenotypes of cancer. In this study, to understand the significance of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK), which is a major aberrant signaling pathway in pancreatic cancer, for the expression of lncRNAs, we performed comparative transcriptome analyses between pancreatic cancer cell lines with or without activation of MAPK. We identified 45 lncRNAs presumably associated with MAPK in pancreatic cancer cells; among these, LINC00941 was consistently upregulated by MAPK. The immediate genomic upstream region flanking LINC00941 was identified as a promoter region, the activity of which was found to be preferentially associated with MAPK activity via ETS-1 binding site. LINC00941 promoted cell proliferation in vitro. Moreover, TCGA data analysis indicated that high expression of LINC00941 was associated with poor prognosis of patients with pancreatic cancer. Transcriptomes comparing transcriptions between cells with and without LINC00941 knockdown revealed 3229 differentially expressed genes involved in 44 biological processes, including the glycoprotein biosynthetic process, beta-catenin-TCF complex assembly, and histone modification. These results indicate that MAPK mediates the aberrant expression of lncRNAs. LINC00941 is the lncRNA by MAPK most consistently promoted, and is implicated in the dismal prognosis of pancreatic cancer. MAPK-associated lncRNAs may play pivotal roles in malignant phenotypes of pancreatic cancer, and as such might represent both potentially valid therapeutic targets and diagnostic biomarkers.