Clapper, Margie L.

Abstract Background: While most EGFR-mutant NSCLC tumors are resistant to checkpoint inhibitors, a small subset has durable responses. Certain molecular subtypes of EGFR may be more responsive. There is a lack of clarity on the genomic and immune profiles of EGFR subtypes, and further elucidation of this may assist in optimally identifying those likely to respond to immune-based therapies. Methods: Profiles of 5,510 lung adenocarcinoma specimens were obtained utilizing next-generation sequencing of 592 genes (Caris Life Sciences) and categorized by EGFR subtype. PD-L1 expression (Ab: 22c3), tumor mutational burden (TMB), immune cell type fractions, and co-mutations in TP53 were assessed by EGFR subtype and compared to wild-type (WT) tumors. Results: Of the total cohort, 791 (14.4%) were EGFR-mutant (Table). Among EGFR-mutant tumors, exon 19 deletions were most common (49.7%), followed by L858R, (32.9%), exon 20 insertions (13.0%), L861Q (2.9%), and G719X (1.5%). PD-L1 positivity of each EGFR subtype as compared to WT did not vary, except for L858R tumors which had a significantly lower percentage of PD-L1 positive cases. Exon 19 deletion, L858R, and exon 20 insertion tumors were significantly less likely to have high PD-L1 or high TMB compared to WT. Among the EGFR subtypes, L861Q and G719X tumors had the greatest percentage with high TMB. TP53 co-mutations were frequent in EGFR tumors, especially among L861Q and G719X tumors. Exon 19 deletion and L858R tumors had significantly less CD8+ and greater CD4+ T cell fractions compared to WT. Neutrophil and M2 macrophage cell fractions were significantly higher in exon 19 deletion, L858R, and exon 20 insertion tumors compared to WT. Conclusions: Most subtypes of EGFR have profiles consistent with decreased immunogenicity; however L861Q and C719X tumors have a greater percentage with high TMB or TP53 co-mutations. Such features in uncommon EGFR subtypes may correlate with responsiveness to immune-based therapies and warrant further study. Tumor Characteristic EGFR WT(n=4719) Exon 19 del(n=393) L858R(n=260) Exon 20 ins(n=103) L861Q(n=23) G719X(n=12) PD-L1 positive (≥1%) 57.7% 51.0% 49.0% a 49.5% 47.8% 50.0% PD-L1 high (≥50%) 30.6% 19.7% a 18.8% a 14.4% a 21.7% 16.7% TMB high (≥10 mut/Mb) 35.3% 1.0% a 3.7% a 1.0% a 9.5% 18.2% TP53 co-mutation 53.9% 61.7% 63.6% a 59.2% a 69.6% a 83.3% a Median % cell fraction CD8+ 0.7 0.3 a 0.4 a 0.3 0.6 0.2 CD4+ 0.0 0.6 a 0.8 a 1.3 a 1.7 1.1 Neutrophils 5.5 8.0 a 7.3 a 7.8 a 7.4 6.4 M2 macrophages 5.5 6.4a 6.9a 6.7a 5.8 4.3 aq-value < 0.05 when compared to EGFR WT (corrected for multiple comparisons) Citation Format: J. Nicholas Bodor, Joanne Xiu, Vinicius Ernani, Supreet Kaur, Hirva Mamdani, Pavel Brodskiy, Sai-Hong I. Ou, Patrick C. Ma, Margie L. Clapper, W. Michael Korn, Joseph Treat. Genomic and immune characteristics of EGFR subtypes in non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4119.

Abstract Metformin is a bi-guanidine employed in treating Type II diabetes. Epidemiologic studies have suggested that diabetics receiving metformin vs thialidizones or insulin have a lower incidence of cancer. In addition, metformin decreases levels of AMPK and IGF1; encouraging its use in both cancer prevention and therapy settings. Most preclinical studies with metformin have employed cell culture or xenografts. We examined its efficacy in multiple in situ animal cancer models. The preventive effect of Metformin administered by gavage or in the diet, at roughly the human equivalent dose (HED), was determined in four standard animal models: (1) methylnitrosourea (MNU)-induced ER+ mammary cancers; (2) MMTV-Neu ER− mammary cancers; (3) hydroxybutyl(butyl)nitrosamine (OH-BBN) induced urinary bladder cancers; and (4) Min mouse model of intestinal tumorigenesis. In the MNU model, Metformin (150 or 50 mg/Kg BW/day) was ineffective as a preventive dose; decreasing neither tumor multiplicity nor latency. Furthermore, both doses increased final tumor weights in treated rats. PK studies at the higher dose of Metformin (150 mg/kg BW/day) showed serum levels slightly higher than humans taking 1.5 g per day. In the MMTV-Neu model, dietary metformin (1200 PPM in diet) decreased the latency of tumor development as well as slightly, but insignificantly, increasing the final tumor multiplicity. Metformin (1200 ppm in diet) in the Min mouse model marginally increased the multiplicity of intestinal adenomas. In contrast, the NSAID naproxen (400 ppm in diet) examined simultaneously in the min mouse strongly inhibited adenoma development. Metformin (150 mg/Kg BW/day) in the OH-BBN induced model of urinary bladder cancer failed to significantly reduce bladder cancers despite relatively high levels of Metformin in the urine. In the MNU model, when rats were placed on a high fat diet to induce a pre-diabetic state, we observed roughly a 20% decrease in tumor multiplicity in the metformin treated rats (P> 0.10). In contrast, tamoxifen and Targretin (an RXR agonist) that were used as positive controls were highly effective in rats on a high fat diet. Metformin didn't decrease tumorigenesis in these standard models, but actually increased tumor formation (incidence, multiplicity, weight) in three of the four models at their HED. These results should particularly discourage any large phase clinical trials in individuals without insulin resistance. The final study certainly raises the question whether the agent might be effective in animals that are diabetic or show insulin resistance Citation Format: Clinton J. Grubbs, Margie L. Clapper, Joel M. Reid, Vernon E. Steele, Ronald A. Lubet. Metformin promotes tumorigenesis in animal models of cancer prevention. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2013-2273