Promoter Methylation and Somatic Mutations in Cancer-Related Genes Are Associated with Hyperprogressive Disease in Patients with Malignant Melanoma and Renal Cell Carcinoma Receiving Anti-PD-1/PD-L1 Immunotherapy.

Background and Objectives: A subset of cancer patients treated with immune checkpoint inhibitors may experience rapid tumor progression rather than therapeutic benefit, a phenomenon described as hyperprogressive disease (HPD), which is linked to poor prognosis and shortened survival. Reliable biomarkers capable of predicting HPD remain lacking. To better understand the molecular background of HPD, we analyzed promoter region methylation and somatic mutation profiles in cancer-related genes in patients with malignant melanoma (MM) and renal cell carcinoma (RCC) undergoing anti-PD-1/PD-L1 treatment. Methods: Patients diagnosed with MM or RCC and treated with anti-PD-1/PD-L1 agents between 2011 and 2020 were included, and FFPE tumor samples along with paired normal tissues were analyzed. A diagnosis of HPD was assigned to patients with RECIST 1.1-defined progressive disease who demonstrated a ≥2-fold acceleration in tumor growth kinetics after initiation of immune checkpoint inhibitor therapy. Methylation-specific real-time PCR was performed on 54 samples (15 MM tumors, 22 RCC tumors, 17 RCC-matched adjacent normal samples) to assess promoter methylation of PIK3CA, BAP1, PTEN, and TP53. Next-generation sequencing (NGS) with an 86-gene pan-cancer panel was conducted on 9 HPD samples. Results: Promoter hypermethylation involving PIK3CA, BAP1, PTEN, and TP53 was more pronounced in HPD-associated tumor samples (n = 16) than in tumors without HPD (n = 21). Within the MM cohort, PTEN and TP53 methylation levels demonstrated statistically significant differences between the two groups (p = 0.005 and p = 0.028, respectively), while no comparable associations were observed in RCC patients. NGS analysis detected missense mutations classified as pathogenic or likely pathogenic in 5 of 9 HPD patients (55.6%), involving KIT, PTEN, and VHL. Conclusions: Promoter region hypermethylation in cancer-related genes may contribute to the aggressive tumor behavior observed in HPD. The somatic variants identified in HPD patients are consistent with known oncogenic pathways. These findings support further investigation of epigenetic and genomic biomarkers for HPD risk stratification in larger, prospective cohorts.