Evolutionary dynamics of tipifarnib in HRAS mutated head and neck squamous cell carcinoma

Abstract

Head and neck squamous cell carcinoma (HNSCC) is a highly prevalent malignancy worldwide, with a significant proportion of patients developing recurrent and/or metastatic (R/M) disease. Despite recent advances in therapy, the prognosis for patients with advanced HNSCC remains poor. Here, we present the case of a patient with recurrent metastatic HNSCC harboring an HRAS G12S mutation who achieved a durable response to treatment with tipifarnib, a selective inhibitor of farnesyltransferase. The patient was a 48-year-old woman who had previously received multiple lines of therapy with no significant clinical response. However, treatment with tipifarnib resulted in a durable partial response that lasted 8 months. Serial genomic and transcriptomic analyses demonstrated upregulation of YAP1 and AXL in metastatic lesions compared with the primary tumor, the evolution of the tumor microenvironment from an immune-enriched to a fibrotic subtype with increased angiogenesis, and activation of the PI3K/AKT/mTOR pathway in tipifarnib treatment. Lastly, in HRAS-mutated PDXs and in the syngeneic HRAS model, we demonstrated that tipifarnib efficacy is limited by activation of the AKT pathway, and dual treatment with tipifarnib and the PI3K inhibitor, BYL719, resulted in enhanced anti-tumor efficacy. Our case study highlights the potential of targeting HRAS mutations with tipifarnib in R/M HNSCC and identifies potential mechanisms of acquired resistance to tipifarnib, along with immuno-, chemo-, and radiation therapy. Preclinical results provide a firm foundation for further investigation of drug combinations of HRAS-and PI3K -targeting therapeutics in R/M HRAS-driven HNSCC.

Keywords: Durable response; Farnesyltransferase inhibitor; HRAS mutation; Head and neck squamous cell carcinoma; Targeted therapy; Tipifarnib.

Figure 1:

Timeline of clinical course and time points of tumor samples obtained from the patient (this scheme was created with BioRender.com). Representative H&E images of the tissue biopsy and positron emission tomography (PET) / computerized tomography (CT) images of the patient at respective time intervals are provided.

Figure 2:

(A) Key biomarkers of patient samples at baseline, progressive metastatic disease, and tumor progression after tipifarnib treatment. Tumor microenvironment subtypes of patient samples at baseline (B), progressive metastatic disease (C), and tumor progression after tipifarnib treatment (D). This planetary schematic represents the molecular and functional characteristics of a patient’s tumor. Blue represents anti-tumor activity and red represents pro-tumor activity. The size of the dots corresponds to the strength of the gene signatures.

Figure 3:

Tumor microenvironment cellular composition of the tumor derived from the patient (A) Baseline/Primary, (B) Progressive Metastatic Disease and (C) Progressive tumor after tipifarnib treatment. (D) Tumor clonal evolution at the three time points at which the tumor was taken for analysis.

Figure 4:

PI3K blockade enhances tipifarnib efficacy in vitro and in vivo. (A) Western blot showing the expression of phosphorylated AKT after tipifarnib treatment for 0 and 120 h in HRAS^V12 shp53 EpT. (B) The ZIP model synergy test was performed using the HRAS^V12 shp53 EpT cell line. The cells were cultured with increasing concentrations of tipifarnib (0–1 μM) or BYL719 (0–20 μM). After four days of treatment, cell viability was determined using crystal violet staining. The results are presented as a ZIP synergy score with 3-D surface plots displaying synergy regions. The synergy experiment was repeated three times, and the representative results from one experiment are presented. (C) Western blotting confirming the blocking of pAKT activation by tipifarnib-BYL719 co-treatment in HRAS^V12 shp53 EpT cells. HRAS^V12 shp53 EpT cells were injected into the lips of WT (D) or NSG (E) mice. After tumors developed (tumor volume ~ 32 mm³), the mice were randomized into four groups and treated daily with the treatment indicated in the graph. Growth kinetics of tumors, (F & G) number of enlarged lymph nodes, and lung metastasis foci following treatment via oral gavage with vehicle, tipifarnib (60 mg/kg twice daily), BYL719 (25 mg/kg once daily), or a combination of the two drugs. (H) PDX were injected or implanted subcutaneously (s.c.) into NSG mice. After tumors developed (tumor volume ~100 mm³), the mice were randomized into four groups and treated daily with the treatment indicated in the graph. Growth kinetics of two HRAS mutant PDX tumors following treatment via oral gavage with vehicle, tipifarnib (60 mg/kg twice daily), BYL719 (40–50 mg/kg once daily), or a combination of the two drugs. P values of 0.05 (*), 0.01 (**), 0.001 (***), and 0.0001 (****) were considered statistically significant. ns, not significant.