Age-associated differences in transcriptional expression and tumor immune microenvironment composition among older patients with cancer.
Authors: Choucair Khalil , Naqash Abdul Rafeh , Salama April K.S. , Kim Chul , Elliott Andrew , Oberley Matthew James , Walker Phillip , Saeed Azhar , El-Deiry Wafik S. , Beltran Himisha , Nabhan Chadi , Liu Stephen V. , Nebhan Caroline , Saeed Anwaar 
Published: June 2022

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Background: Older patients (pts) with cancer are underrepresented in registrational clinical trials for immune checkpoint inhibitor (ICI) therapies. There may be relevant differences in the makeup of the tumor microenvironment (TME) and in genomic signatures of cancer in older pts. This analysis explores differences in the genomic makeup of common cancers and their TME in pts ≥ 80 years (yr) of age, compared to younger pts. Methods: Next-generation sequencing of DNA (592 gene panel, NextSeq or whole-exome sequencing, NovaSeq) and RNA (whole transcriptome sequencing, NovaSeq) was performed for non-small cell lung carcinoma (NSCLC; n = 19,891), melanoma (MEL n = 2,899), and renal cell carcinoma (RCC; n = 1,333) pt samples submitted to a CLIA-certified laboratory (Caris Life Sciences, Phoenix, AZ). PD-L1 expression was assessed by immunohistochemistry (IHC), and high tumor mutational burden (TMB-H) was defined as ≥10 mut/Mb. Pts were stratified into age subgroups of ≥80 and < 80 yr for comparison of DNA damage response (DDR) gene alterations, gene expression profiling, and TME analysis (MCP-counter; Becht, 2016). P-values were adjusted for multiple hypotheses testing (Benjamini-Hochberg) unless noted as exploratory. Results: Pts ≥80 yr accounted for 16.0%, 19.9% and 5.3% of NSCLC, MEL and RCC pts, respectively. Compared to pts < 80 yr, NSCLC and MEL pts ≥80 yr had similar DDR gene mutation rates, while BRCA1 mutations were more common in MEL pts ≥80 yr (2.1 vs 0.8%; exploratory- p < 0.05). NSCLC ≥80 yr TMEs had increased abundance of fibroblasts (1.09-fold, p < 0.01), dendritic cells (1.07-fold, p < 0.01) and macrophages (1.04-fold, p < 0.01), and MEL≥80 yr TMEs had fewer infiltrating T-lymphocytes (0.87-fold, p = 0.02). Increased expression of immune checkpoint (IC) genes PDCDL1G2 (PD-L2; 1.11-fold), HAVCR2 (TIM-3; 1.11-fold ), and CD80/86 (1.07/1.08-fold, p < 0.05) was seen in NSCLC pts ≥80 yr, while IL-6 expression was decreased (0.88-fold; p < 0.05). The largest change in IC gene expression was for IL-6 (1.24-fold, p = 0.78) in MEL, and GZMB (0.56-fold ; p = 0.17) in RCC ≥80 yr. TMB-H was less common in NSCLC (29.7 vs 36.5%, p < 0.001) and more common in MEL pts ≥80 yr (65.7 vs 49.0%, p < 0.01), and PD-L1 (IHC-SP142, ≥2+|5%) expression was less frequent in RCC pts ≥80 yr (9.1 vs 19.4%, exploratory p < 0.05). Profiling of glutamine and glucose metabolism-related genes revealed increased SLC38A5 (1.17-fold; p < 0.0001) and decreased G6PC (0.65-fold, p < 0.01) expression in NSCLC ≥80 yr. While not statistically significant, MEL and RCC pts ≥80 yr had opposite trends for SLC38A5 and G6PC expression. Conclusions: Our analysis provides new insights to immune landscape of NSCLC, MEL, and RCC pts ≥80 yr. Differential gene expression and TME composition changes in this population suggest unique, cancer-specific therapeutic opportunities, and a potential to explore biomarkers of response to ICIs.