Functional and biological heterogeneity of KRAS ^Q61 mutations

Abstract

Missense mutations at the three hotspots in the guanosine triphosphatase (GTPase) RAS—Gly 12 , Gly 13 , and Gln 61 (commonly known as G12, G13, and Q61, respectively)—occur differentially among the three RAS isoforms. Q61 mutations in KRAS are infrequent and differ markedly in occurrence. Q61H is the predominant mutant (at 57%), followed by Q61R/L/K (collectively 40%), and Q61P and Q61E are the rarest (2 and 1%, respectively). Probability analysis suggested that mutational susceptibility to different DNA base changes cannot account for this distribution. Therefore, we investigated whether these frequencies might be explained by differences in the biochemical, structural, and biological properties of KRAS Q61 mutants. Expression of KRAS Q61 mutants in NIH 3T3 fibroblasts and RIE-1 epithelial cells caused various alterations in morphology, growth transformation, effector signaling, and metabolism. The relatively rare KRAS Q61E mutant stimulated actin stress fiber formation, a phenotype distinct from that of KRAS Q61H/R/L/P , which disrupted actin cytoskeletal organization. The crystal structure of KRAS Q61E was unexpectedly similar to that of wild-type KRAS, a potential basis for its weak oncogenicity. KRAS Q61H/L/R -mutant pancreatic ductal adenocarcinoma (PDAC) cell lines exhibited KRAS-dependent growth and, as observed with KRAS G12 -mutant PDAC, were susceptible to concurrent inhibition of ERK-MAPK signaling and of autophagy. Our results uncover phenotypic heterogeneity among KRAS Q61 mutants and support the potential utility of therapeutic strategies that target KRAS Q61 mutant–specific signaling and cellular output.

SOS1 and KSR1 modulate MEK inhibitor responsiveness to target resistant cell populations based on PI3K and KRAS mutation status

“…KRAS is commonly mutated at one of three mutational hotspots, G12, G13, or Q61 [4]; mutation of one of these sites alters KRAS GTP/GDP cycling leading to increased KRAS-GTP loading and hyperactivation of downstream effectors including the proproliferative RAF/MEK/ERK kinase cascade. The RAF/MEK/ERK kinase cascade is the critical driver of proliferation in KRAS-mutated cancers [5][6][7][8][9], and multiple small molecule inhibitors of each kinase have been evaluated in KRAS-mutated cancers [10]. Of these, the MEK inhibitors trametinib and selumetinib are among the most promising agents [11,12].…”

Overlapping and Distinct Functions of an Extended Repertoire of KRAS Mutations

“…Thus, knowledge gained herein will shape future studies into the opportunities to intervene or interrogate cells driven to differently perturbed biologic states due to distinct KRAS mutations. While other labs have shown heterogeneity due to different KRAS alleles 10,28,29 , previous work has been accomplished in heterogeneous systems, been limited to one domain of information, such as an enzymatic or cellular readout, or studied a limited set of mutations. We used a uniform system to characterize all major KRAS mutations observed across human cancer types.…”

RAS‐targeted cancer therapy: Advances in drugging specific mutations

“…During therapy, KRAS G12D lung cancer clone of the patient with stage III NSCLC appeared to disappear. RAL Essential for tumor growth and invasion 223,224 Maintaining tumor 279 --KRAS G12D/G12V -CRAF Dispensable for tumor development 168,169 KRAS G12C/G12D/Q61X Increased autophagic flux after suppression of KRAS 280,281 ERK Increased autophagic flux after suppression of ERK Endometrial cancer KRAS mutation Inducing early EC 284 and development…”