Abstract 2735: Clinico-pathological and molecular features associated with TP53 mutation in 3457 molecularly-profiled colorectal cancers (CRCs)
Authors: Xiu Joanne , Soussi Thierry , Bender Ryan , Reddy Sandeep , El-Deiry Wafik S. 
Published: July 2016

Deregulation of the p53 tumor suppressor gene (TP53) is a key event contributing to transformation and aggressive metastatic features of CRC. Patients with TP53 mutation are often resistant to therapy and carry a poor prognosis. We investigated TP53 mutation in a cohort of 3457 CRCs to identify molecular features specific to TP53-mutated CRC tumors. The 3457 CRC clinical samples were evaluated for tumor profiling (Caris Life Sciences, Phoenix, AZ). Tests included Sanger or next generation sequencing (NGS), protein expression by immunohistochemistry (IHC) and gene amplification by in situ hybridization (ISH). TP53 mutation was observed in 2106 or 61% of CRCs analyzed. 2018 or 96% of these mutant TP53 tumors carried one TP53 mutation, 83 (4%) carried 2 mutations, 4 carried 3 and 1 tumor carried 4 mutations. Among the ∼2200 mutations found in TP53, 37% were found at one of the six hotspots within the DNA binding domain (R175, G245, R248, R249, R273 and R282). Overall, 1554 (71%) were missense mutations, 367 (17%) nonsense, 209 (9.5%) frameshift, 45 (2%) small in-frame in-dels, and 25 (1.1%) mutations that affect splicing. In this cohort, TP53 mutation was more prevalent in male patients (64% vs. 57%, P&lt;0.0001) and was more likely to occur in tumors that originated from the left colon (69%) as compared to the right colon (45%, p&lt;0.0001). TP53 mutation rate was not correlated with patient age, histology or whether the tumor sample was taken from the primary or metastatic sites. When the molecular features of TP53-mutated tumors were compared to those of wild-type TP53, mutated tumors carried significantly higher Her2 IHC expression (2.5% vs. 1.0%, p = 0.0039) and gene amplification (3.7% vs. 1.4%, p = 0.0002), as well as higher MGMT (61% vs. 53%, p&lt;0.0001) and TOPO2A expression (92% vs. 81%, p&lt;0.0001). On the other hand, lower EGFR expression (57.4% vs. 70%, p&lt;0.0001), PTEN expression (47.9% vs. 61%, p&lt;0.0001), microsatellite instability (2.5% vs. 11.5%, p&lt;0.0001), ERCC1 (18% vs. 24%, p&lt;0.0001) and TS expression (31% vs. 38%, p&lt;0.0001) were associated with TP53-mutated tumors. TP53-mutated CRCs carried higher rates of APC mutation (63% vs. 53%, p&lt;0.0001), but lower rates of KRAS (46% vs. 54%, p&lt;0.0001), PIK3CA (11.6% vs. 22%, p&lt;0.0001), PTEN (2% vs. 5.2%, p&lt;0.0001), GNAS (1% vs. 8.3%, p&lt;0.0001) and AKT1 (0.6% vs. 1.7%, p = 0.0016) mutation. In this cohort of 3457 molecularly profiled CRCs, TP53 mutation was more prevalent in males and tumors that originated from the left colon. Distinct molecular features associated with TP53 mutation in CRC included lower frequency of PI3K/Akt/mTor pathway activation and were more likely to be microsatellite stable.. Our findings suggest differential presence of therapeutic targets in CRC tumors based on TP53 mutation status.

Citation Format: Joanne Xiu, Thierry Soussi, Ryan Bender, Sandeep Reddy, Wafik S. El-Deiry. Clinico-pathological and molecular features associated with TP53 mutation in 3457 molecularly-profiled colorectal cancers (CRCs). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2735.