Adipocyte Precursor-Derived NRG1 Promotes Resistance to FGFR Inhibition in Urothelial Carcinoma

Sonodynamic Therapy by Reactive Oxygen Species Generation-Responsive Pseudo-Semiconducting Polymer Nanoparticles Combined with a Fibroblast Growth Factor Receptor Inhibitor for Enhancing Immunotherapy in Bladder Cancer

Sonodynamic therapy, a treatment modality recently widely used, is capable of disrupting the tumor microenvironment by inducing immunogenic cell death (ICD) and enhancing antitumor immunity during immunotherapy. Erdafitinib, an inhibitor of the fibroblast growth factor receptor, has demonstrated potential benefits for treating bladder cancer. However, Erdafitinib shows effectiveness in only a small number of patients, and the majority of patients responding positively to the medication have "immune-cold" tumors. To increase the therapeutic efficacy of Erdafitinib, we have herein developed a biodegradable pseudoconjugate polymer (PSP) with sonodynamic capabilities. Erdafitinib could be efficiently encapsulated in nanoparticles (NP-PE) prepared through the self-assembly of PSP with an oxidation-sensitive polymer (P1). Under ultrasound conditions, NP-PE effectively induced cytotoxicity by producing reactive oxygen species and further triggering ICD. Compared with Erdafitinib, NP-PE inhibited the expression of FGFR3 to a higher extent. In animal models with bladder cancer, NP-PE inhibited tumor growth, stimulated antitumor immunity, and synergized with antiprogrammed cell death-ligand 1 (aPD-L1), offering a novel approach for the treatment of bladder cancer.

FGFR Inhibition in Urothelial Carcinoma

BACKGROUND AND OBJECTIVE

The 2024 US Food and Drug Administration approval of erdafitinib for the treatment of metastatic urothelial carcinoma (mUC) with FGFR3 alterations ushered in the era of targeted therapy for bladder cancer. In this review, we summarize the effects of FGFR pathway alterations in oncogenesis, clinical data supporting FGFR inhibitors in the management of bladder cancer, and the challenges that remain.

METHODS

Original articles relevant to FGFR inhibitors in urothelial cancer between 1995 and 2024 were systematically identified in the PubMed and MEDLINE databases using the search terms "FGFR" and "bladder cancer". An international expert panel with extensive experience in FGFR inhibitor treatment was convened to synthesize a collaborative narrative review.

KEY FINDINGS AND LIMITATIONS

Somatic FGFR3 alterations are found in up to 70% of low-grade non-muscle-invasive bladder cancers; these activate downstream signaling cascades and culminate in cellular proliferation. Beyond a link to lower-grade/lower-stage tumors, there is little consistency regarding whether these alterations confer prognostic risks for cancer recurrence or progression. FGFR3-altered tumors have been linked to a non-inflamed tumor microenvironment, but paradoxically do not seem to impact the response to systemic immunotherapy. Several pan-FGFR inhibitors have been investigated in mUC. With the introduction of novel intravesical drug delivery systems, FGFR inhibitors are poised to transform the therapeutic landscape for early-stage UC.

CONCLUSIONS AND CLINICAL IMPLICATIONS

With deepening understanding of the biology of bladder cancer, novel diagnostics, and improved drug delivery methods, we posit that FGFR inhibition will lead the way in advancing precision treatment of bladder cancer.

Adipose Stromal Cell-Derived Cancer-Associated Fibroblasts Suppress FGFR Inhibitor Efficacy

Cancer aggressiveness has been linked with obesity, and studies have shown that adipose tissue can enhance cancer progression. In this issue of Cancer Research, Hosni and colleagues discover a paracrine mechanism mediated by adipocyte precursor cells through which urothelial carcinomas become resistant to erdafitinib, a recently approved therapy inhibiting fibroblast growth factor receptors (FGFR). They identified neuregulin 1 (NRG1) secreted by adipocyte precursor cells as an activator of HER3 signaling that enables resistance. The NRG1-mediated FGFR inhibitor resistance was amenable to intervention with pertuzumab, an antibody blocking the NRG1/HER3 axis. To investigate the nature of the resistance-associated NRG1-expressing cells in human patients, the authors analyzed published single-cell RNA sequencing data and observed that such cells appear in a cluster assigned as inflammatory cancer-associated fibroblasts (iCAF). Notably, the gene signature corresponding to these CAFs is highly similar to that shared by adipose stromal cells (ASC) in fat tissue and fibro-adipogenic progenitors (FAP) in skeletal muscle of cancer-free individuals. Because fibroblasts with the ASC/FAP signature are enriched in various carcinomas, it is possible that the paracrine signaling conferred by NRG1 is a pan-cancer mechanism of FGFR inhibitor resistance and tumor aggressiveness. See related article by Hosni et al., p. 725.