Ray Paramita, Shukla Shirish, Zhang Yaqing, Donahue Katelyn L, Nancarrow Derek J, Kasturirangan Srimathi, Shankar Sunita, Cuneo Kyle, Thomas Dafydd, Gadgeel Shirish M, Lawrence Theodore S, Pasca di Magliano Marina, Ray Dipankar
Department of Radiation Oncology, The University of Michigan Medical School, Ann Arbor, Michigan.
Department of Surgery, The University of Michigan Medical School, Ann Arbor, Michigan.
Mol Cancer Res. 2025 Jun 3;23(6):530-541. doi: 10.1158/1541-7786.MCR-24-0701.
Cooperativity between mutant p53 and mutant KRAS, although recognized, is poorly understood. In pancreatic cancer, mutant p53 induces splicing factor hnRNPK, causing an isoform switch that produces overexpression of GTPase-activating protein 17 isoform 1 (GAP17-1). GAP17-1 is mislocalized in the cytosol instead of the membrane, owing to the insertion of exon 17 encoding a PPLP motif, thus allowing mutant KRAS to remain in the GTP-bound hyperactive state. However, the role of PPLP in influencing GAP17-1 mislocalization remains unclear. We show that Smad ubiquitination regulatory factor 2 (SMURF2), a known stabilizer of mutant KRAS, interacts with GAP17-1 via the PPLP motif and displaces it from the membrane, facilitating mutant p53-mediated mutant KRAS hyperactivation. We used cell lines with known KRAS and TP53 mutations, characterized SMURF2 expression in multiple pancreatic cancer mouse models (iKras*; iKras*, p53*, and p48-Cre; Kras*), and performed single-cell RNA sequencing and tissue microarray on preclinical and clinical samples. We found that SMURF2 silencing profoundly reduces the survival of mutant TP53; KRAS-driven cells. We show that a GAP17-1 AALA mutant does not bind to SMURF2, stays in the membrane, and keeps mutant KRAS in the GDP-bound state to inhibit downstream signaling. In mouse models, mutant KRAS and SMURF2 upregulation are correlated with pancreatic intraepithelial neoplasia and ductal adenocarcinoma lesions. Furthermore, patients with pancreatic ductal adenocarcinoma who received neoadjuvant therapy and express moderate-to-high SMURF2 show decreased overall survival (P = 0.04).
In TP53 and KRAS double-mutated pancreatic cancer, SMURF2-driven GAP17-1 membrane expulsion facilitates mutant p53-KRAS oncogenic synergy.
突变型p53与突变型KRAS之间的协同作用虽然已被认识，但了解甚少。在胰腺癌中，突变型p53诱导剪接因子hnRNPK，导致异构体转换，产生GTP酶激活蛋白17异构体1（GAP17-1）的过表达。由于编码PPLP基序的外显子17的插入，GAP17-1定位于细胞质而非膜上，从而使突变型KRAS保持在GTP结合的高活性状态。然而，PPLP在影响GAP17-1错误定位中的作用仍不清楚。我们发现，已知的突变型KRAS稳定剂Smad泛素化调节因子2（SMURF2）通过PPLP基序与GAP17-1相互作用，并将其从膜上置换下来，促进突变型p53介导的突变型KRAS过度激活。我们使用了具有已知KRAS和TP53突变的细胞系，在多个胰腺癌小鼠模型（iKras*；iKras*、p53和p48-Cre；Kras）中对SMURF2表达进行了表征，并对临床前和临床样本进行了单细胞RNA测序和组织微阵列分析。我们发现，沉默SMURF2可显著降低突变型TP53；KRAS驱动细胞的存活率。我们表明，GAP17-1 AALA突变体不与SMURF2结合，保留在膜上，并使突变型KRAS保持在GDP结合状态以抑制下游信号传导。在小鼠模型中，突变型KRAS和SMURF2的上调与胰腺上皮内瘤变和导管腺癌病变相关。此外，接受新辅助治疗且表达中度至高SMURF2的胰腺导管腺癌患者的总生存期降低（P = 0.04）。
在TP53和KRAS双突变的胰腺癌中，SMURF2驱动的GAP17-1膜排斥促进了突变型p53-KRAS致癌协同作用。
