Abstract 2267: Alterations in TGFβ signaling in ovarian cancer patients with TGFβ receptor 1 variants

Abstract Transforming growth factor β (TGFβ) signals through the TGFβ Receptor 1 (TGFβR1) and is implicated in many aspects of malignancy. TGFβR1 gene is frequently mutated in ovarian carcinomas (OvCa) (Chen, T., et al, Cancer Research 61, 4679-4682, 2001). Susceptibility to numerous cancers is linked to two germline variants of TGFβR1, a G to A single nucleotide polymorphism in intron 7 (Int 7G24A) and a nine base pair deletion in exon 1 (TGFβR1*6A) although the mechanism(s) for this association is still unclear. Since the canonical pathway for TGFβR1 signaling is via phosphorylation of SMAD, the goal was to determine the association of either or both variants with development of subtypes of OvCa and to measure phosphorylation of pSMAD in the epithelium and stroma of OvCas from women with either or both Int 7G24A and TGFβR1*6A. FFPE tissues from 122 women without a history of cancer, and 59 women with OvCa were obtained from St. Elizabeth Healthcare (N. KY) and from 63 women with OvCa through the Cooperative Human Tissue Network (Birmingham Ala). OvCa patients and non-cancer controls were age matched. St. Elizabeth Healthcare IRB gave permission for this study. Tumors were diagnosed in H&E stained histologic sections by a Board Certified Pathologist (LED) and were classified as either Low Malignant Potential (LMP), Type 1 (clear cell, mucinous and low grade serous and endometrioid) or Type 2 (high grade serous, high grade endometrioid, or carcinosarcoma). Variants were identified in extracted DNA from FFPE tissues using PCR, capillary electrophoresis (CE), RFLP, and SSCP. Histologic sections were stained by IHC using the DAKO LSAB2 kit (Agilent) and anti pSMAD 2 (Millipore AB3849-1). Stain was evaluated as cytoplasmic and nuclear Histoscores (stain Area X Intensity) by two observers (LED, JHC). Data were evaluated by “Gene Code” with Gene 1 wild type for both variants, Gene 2 homozygous or heterozygous for Int 7G24A, Gene 3 homozygous or heterozygous for TGFβR1*6A, and Gene 4 having both variants. Usual chi-tests were used to determine significance of contingency tables, ANOVA with multiple comparison adjusted were used for markers. KM plots and proportional hazards were used in survival tests. The frequency in Gene 1, 2, 3, and 4 was significantly different in controls vs. OvCa patients (p = 0.0010); 57.7% of OvCa patients had a TGFβR1 variant vs. 36.6% of controls. Frequency of TGFβR1 variants in 62 patients with Type 2 OvCa was 62.9%. Patient survival differed significantly between patients with LMP, Type 1, and Type 2 OvCa (p <0.0001). Differences in nuclear expression of pSMAD in both tumor epithelial and stromal cells between OvCa types were highly significant (p < 0.0001, p< 0.0092). pSMAD expression decreased significantly in the nuclei of both epithelial and stromal cells in Type 2 tumors. These data indicate that germline variations in the TGFβR1 gene are associated with high grade ovarian cancers and altered SMAD phosphorylation. Citation Format: Julia H. Carter, James P. Schaeper, Taiping Chen, Diane W. Fritz, Leah Focke, Adrian Guy, James A. Deddens, Larry E. Douglass. Alterations in TGFβ signaling in ovarian cancer patients with TGFβ receptor 1 variants [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2267.