Somatic rearrangements causing oncogenic ectodomain deletions of FGFR1 in squamous cell lung cancer

A Case of Lung Squamous Cell Carcinoma Harboring TP53 Mutation and PLPP5-FGFR1 Fusion Gene

Lung squamous cell carcinoma (LUSC) is one of the most common subtype of lung cancer and is associated with the poor prognoses. The fibroblast growth factor receptor (FGFR) family is known to be activated through fusions with various partners across multiple cancer types, including nonsmall cell lung cancer (NSCLC). FGFR inhibitors are currently undergoing clinical evaluation for the treatment of tumors harboring these fusions. While FGFR1 amplification has been well-documented in numerous NSCLC datasets, the characterization of specific FGFR fusion variants remains limited. In this study, we identified a novel PLPP5-FGFR1 fusion in a 65-year-old male patient with lung squamous cell carcinoma through targeted RNA sequencing. The fusion junction was located between exon 1 of PLPP5 and exon 5 of FGFR1, and the result was validated by Sanger sequencing. To our knowledge, this is the first reported case of a PLPP5-FGFR1 fusion coexisting with a TP53 mutation in LUSC. These findings broaden the spectrum of potential translocation partners in FGFR1 fusions, and the clinical implications of this novel fusion on treatment outcomes and prognosis warrant further investigation and long-term follow-up.

Clinical advances and challenges in targeting FGF/FGFR signaling in lung cancer

Fibroblast growth factors (FGFs) and their receptors regulate numerous cellular processes, such as metabolism and signal transduction, but can also drive tumorigenesis. Specifically, in lung cancer, the overexpression of FGFs, as well as the amplification, mutation and fusion of FGFR genes, are closely linked to the initiation, progression and resistance of the disease, suggesting that targeting FGF/FGFR is an attractive therapeutic strategy for lung cancer treatment. Nintedanib, a multitarget tyrosine kinase inhibitor (TKI) used in combination with docetaxel, has shown some success as a second-line therapy for lung cancer. However, clinical trials evaluating other FGFR inhibitors have yielded mixed results, indicating substantial complexity in targeting aberrant FGF/FGFR signaling. In this review, we describe the aberrations in FGF/FGFR signaling in lung cancer and summarize the clinical efficacy of FGFR inhibitors, such as multitarget TKIs, selective FGFR-TKIs and biological agents. We also discuss various challenges associated with FGFR targeting in lung cancer, including precision patient selection, toxicity and resistance. Finally, we provide perspectives on future directions, namely, developing novel FGFR-targeting drugs, such as FGFR degraders and more specific FGFR-TKIs, adopting combination therapy and targeting FGFs.

Genomic insights into the mechanisms of FGFR1 dependency in squamous cell lung cancer

Although subsets of patients with lung squamous cell carcinoma (LSCC) benefit from immunotherapy, there are few effective molecularly targeted treatments for LSCC. Fibroblast growth factor receptor (FGFR) inhibitors provide a therapeutic option for patients with LSCC harboring FGFR aberrations, but their therapeutic efficacy has been limited to date. In this issue of the JCI, Malchers et al. identified tail-to-tail rearrangements, either within or near FGFR1, that are associated with FGFR1 dependency and sensitivity to FGFR inhibition in LSCC. These results may help improve the selection of patients with LSCC who are most likely to benefit from treatment with FGFR inhibitors.