Atypical KRAS(G12R) Mutant Is Impaired in PI3K Signaling and Macropinocytosis in Pancreatic Cancer.

Allele-specific signaling by different KRAS alleles remains poorly understood. The KRAS G12R mutation displays uneven prevalence among cancers that harbor the highest occurrence of KRAS mutations: It is rare (∼1%) in lung and colorectal cancers, yet relatively common (∼20%) in pancreatic ductal adenocarcinoma (PDAC), suggesting context-specific properties. We evaluated whether KRASG12R is functionally distinct from the more common KRASG12D- or KRASG12V-mutant proteins (KRASG12D/V). We found that KRASG12D/V but not KRASG12R drives macropinocytosis and that MYC is essential for macropinocytosis in KRASG12D/V- but not KRASG12R-mutant PDAC. Surprisingly, we found that KRASG12R is defective for interaction with a key effector, p110α PI3K (PI3Kα), due to structural perturbations in switch II. Instead, upregulated KRAS-independent PI3Kγ activity was able to support macropinocytosis in KRASG12R-mutant PDAC. Finally, we determined that KRASG12R-mutant PDAC displayed a distinct drug sensitivity profile compared with KRASG12D-mutant PDAC but is still responsive to the combined inhibition of ERK and autophagy. SIGNIFICANCE: We determined that KRASG12R is impaired in activating a key effector, p110α PI3K. As such, KRASG12R is impaired in driving macropinocytosis. However, overexpression of PI3Kγ in PDAC compensates for this deficiency, providing one basis for the prevalence of this otherwise rare KRAS mutant in pancreatic cancer but not other cancers.See related commentary by Falcomatà et al., p. 23.This article is highlighted in the In This Issue feature, p. 1.

Hobbs GA ，Baker NM ，Miermont AM ，Thurman RD ，Pierobon M ，Tran TH ，Anderson AO ，Waters AM ，Diehl JN ，Papke B ，Hodge RG ，Klomp JE ，Goodwin CM ，DeLiberty JM ，Wang J ，Ng RWS ，Gautam P ，Bryant KL ，Esposito D ，Campbell SL ，Petricoin EF 3rd ，Simanshu DK ，Aguirre AJ ，Wolpin BM ，Wennerberg K ，Rudloff U ，Cox AD ，Der CJ ... -  《-》

ADT-1004: a first-in-class, oral pan-RAS inhibitor with robust antitumor activity in preclinical models of pancreatic ductal adenocarcinoma.

Oncogenic KRAS mutations occur in nearly, 90% of patients with pancreatic ductal adenocarcinoma (PDAC). Targeting KRAS has been complicated by mutational heterogeneity and rapid resistance. We developed a novel pan-RAS inhibitor, ADT-1004 (an oral prodrug of ADT-007) and evaluated antitumor activity in murine and human PDAC models. Murine PDAC cells with KRASG12D mutation (KPC-luc or 2838c3-luc) were orthotopically implanted into the pancreas of C57BL/6J mice, and four PDX PDAC tumors with KRAS mutations were implanted subcutaneously in NSG mice. To assess potential to overcome RAS inhibitor resistance, parental and resistant MIA PaCa-2 PDAC cells (KRASG12C mutation) were implanted subcutaneously. Subcutaneously implanted RASWT BxPC-3 cells were used to assess the selectivity of ADT-1004. ADT-1004 potently blocked tumor growth and RAS activation in mouse PDAC models without discernable toxicity with target engagement and reduced activated RAS and ERK phosphorylation. In addition, ADT-1004 suppressed tumor growth in PDX PDAC models with KRASG12D, KRASG12V, KRASG12C, or KRASG13Q mutations and increased CD4+ and CD8+ T cells in the TME consistent with exhaustion and increased MHCII+ M1 macrophage and dendritic cells. ADT-1004 demonstrated superior efficacy over sotorasib and adagrasib in tumor models resistant to these KRASG12C inhibitors and MRTX1133 resistant KRASG12D mutant cells. As evidence of selectivity for tumors with mutant KRAS, ADT-1004 did not impact the growth of tumors from RASWT PDAC cells. ADT-1004 has strong antitumor activity in aggressive and clinically relevant PDAC models with unique selectivity to block RAS-mediated signaling in RAS mutant cells. As a pan-RAS inhibitor, ADT-1004 has broad activity and potential efficacy advantages over allele-specific KRAS inhibitors. These findings support clinical trials of ADT-1004 for KRAS mutant PDAC.

Bandi DSR ，Nagaraju GP ，Sarvesh S ，Carstens JL ，Foote JB ，Graff EC ，Fang YD ，Keeton AB ，Chen X ，Valiyaveettil J ，Berry KL ，Bae S ，Akce M ，Gorman G ，Yoon KJ ，Manne U ，Boyd MR ，Buchsbaum DJ ，Azmi AS ，Maxuitenko YY ，Piazza GA ，El-Rayes BF ... -  《Molecular Cancer》

AGER-dependent macropinocytosis drives resistance to KRAS-G12D-targeted therapy in advanced pancreatic cancer.

Li C ，Liu Y ，Liu C ，Chen F ，Xie Y ，Zeh HJ ，Yu C ，Liu J ，Tang D ，Kang R ... -  《-》

Concurrent Inhibition of the RAS-MAPK Pathway and PIKfyve Is a Therapeutic Strategy for Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by KRAS- and autophagy-dependent growth. Inhibition of the KRAS-RAF-MEK-ERK pathway enhances autophagic flux and dependency, and concurrent treatment with the nonspecific autophagy inhibitor chloroquine (CQ) and ERK-MAPK pathway inhibitors can synergistically block PDAC growth. However, CQ is limited in terms of specificity and potency. To find alternative anti-autophagy strategies, in this study, we performed a CRISPR-Cas9 loss-of-function screen in PDAC cell lines that identified the lipid kinase phosphatidylinositol-3-phosphate 5-kinase (PIKfyve) as a growth-promoting gene. PIKfyve inhibition by the small molecule apilimod resulted in durable growth suppression, with much greater potency than CQ treatment. PIKfyve inhibition caused lysosomal dysfunction, reduced autophagic flux, and led to the accumulation of autophagy-related proteins. Furthermore, PIKfyve inhibition blocked the compensatory increases in autophagic flux associated both with MEK inhibition and with direct RAS inhibition. Accordingly, combined inhibition of PIKfyve and the RAS-MAPK pathway showed robust growth suppression across a panel of KRAS-mutant PDAC models. Growth suppression was due, in part, to potentiated cell-cycle arrest and induction of apoptosis following loss of inhibitor of apoptosis proteins. These findings indicate that concurrent inhibition of RAS and PIKfyve is a synergistic, cytotoxic combination that may represent a therapeutic strategy for PDAC. Significance: PIKfyve inhibition effectively blocks autophagy in multiple models of KRAS-mutant pancreatic cancer and can synergize with inhibitors of members of the RAS-MAPK pathway, providing an effective combination strategy for pancreatic cancer.

DeLiberty JM ，Roach MK ，Stalnecker CA ，Robb R ，Schechter EG ，Pieper NL ，Taylor KE ，Pita LM ，Yang R ，Bang S ，Drizyte-Miller K ，Ackermann SE ，Nicewarner Peña SR ，Baldelli E ，Min SM ，Drewry DH ，Petricoin EF 3rd ，Morris JP 4th ，Der CJ ，Cox AD ，Bryant KL ... -  《-》

Pancreatic cancer-derived extracellular vesicles enhance chemoresistance by delivering KRAS(G12D) protein to cancer-associated fibroblasts.

KRAS mutations are instrumental in the development and progression of pancreatic ductal adenocarcinoma (PDAC). Nevertheless, the efficacy of direct targeting of KRAS mutations to inhibit tumor development remains doubtful. It is therefore necessary to gain a deeper insight into the mechanism in which KRAS mutations influence the effectiveness of clinical treatments. In this study, KRASG12D protein was detected in cancer-associated fibroblasts (CAFs) from clinical samples of PDAC. In vitro experiments demonstrated that KRASG12D protein in CAFs was not expressed from its own mutant gene but was derived from the ingestion of tumor cell-derived extracellular vesicles (EVs). The presence of KRASG12D protein in CAFs resulted in enhanced proliferation and migration. Furthermore, KRASG12D-containing CAFs were observed to promote tumor chemoresistance to gemcitabine treatment both in vitro and in vivo. Application of a KRAS mutation-specific inhibitor, MRTX1133, has been demonstrated to reverse chemoresistance in PDAC. Moreover, clinical data suggest that patients with KRAS mutations have poorer prognosis following adjuvant chemotherapy. These findings elucidate the mechanism by which oncogenic KRAS mutations promote cancer chemoresistance and remodel tumor environment in a non-autonomous manner, suggesting a novel strategy for targeting KRAS mutations to enhance chemosensitivity in PDAC.

Liu X ，Yang J ，Huang S ，Hong Y ，Zhu Y ，Wang J ，Wang Y ，Liang T ，Bai X ... -  《-》