AXL and Error-Prone DNA Replication Confer Drug Resistance and Offer Strategies to Treat EGFR-Mutant Lung Cancer.

Anticancer therapies have been limited by the emergence of mutations and other adaptations. In bacteria, antibiotics activate the SOS response, which mobilizes error-prone factors that allow for continuous replication at the cost of mutagenesis. We investigated whether the treatment of lung cancer with EGFR inhibitors (EGFRi) similarly engages hypermutators. In cycling drug-tolerant persister (DTP) cells and in EGFRi-treated patients presenting residual disease, we observed upregulation of GAS6, whereas ablation of GAS6's receptor, AXL, eradicated resistance. Reciprocally, AXL overexpression enhanced DTP survival and accelerated the emergence of T790M, an EGFR mutation typical to resistant cells. Mechanistically, AXL induces low-fidelity DNA polymerases and activates their organizer, RAD18, by promoting neddylation. Metabolomics uncovered another hypermutator, AXL-driven activation of MYC, and increased purine synthesis that is unbalanced by pyrimidines. Aligning anti-AXL combination treatments with the transition from DTPs to resistant cells cured patient-derived xenografts. Hence, similar to bacteria, tumors tolerate therapy by engaging pharmacologically targetable endogenous mutators. SIGNIFICANCE: EGFR-mutant lung cancers treated with kinase inhibitors often evolve resistance due to secondary mutations. We report that in similarity to the bacterial SOS response stimulated by antibiotics, endogenous mutators are activated in drug-treated cells, and this heralds tolerance. Blocking the process prevented resistance in xenograft models, which offers new treatment strategies. This article is highlighted in the In This Issue feature, p. 2483.

Cross-talk between mutant p53 and p62/SQSTM1 augments cancer cell migration by promoting the degradation of cell adhesion proteins.

Missense mutations in the p53 tumor suppressor abound in human cancer. Common ("hotspot") mutations endow mutant p53 (mutp53) proteins with oncogenic gain of function (GOF), including enhanced cell migration and invasiveness, favoring cancer progression. GOF is usually attributed to transcriptional effects of mutp53. To elucidate transcription-independent effects of mutp53, we characterized the protein interactome of the p53R273H mutant in cells derived from pancreatic ductal adenocarcinoma (PDAC), where p53R273H is the most frequent p53 mutant. We now report that p53R273H, but not the p53R175H hotspot mutant, interacts with SQSTM1/p62 and promotes cancer cell migration and invasion in a p62-dependent manner. Mechanistically, the p53R273H-p62 axis drives the proteasomal degradation of several cell junction­associated proteins, including the gap junction protein Connexin 43, facilitating scattered cell migration. Concordantly, down-regulation of Connexin 43 augments PDAC cell migration, while its forced overexpression blunts the promigratory effect of the p53R273H-p62 axis. These findings define a mechanism of mutp53 GOF.

Context- and dose-dependent modulatory effects of naringenin on survival and development of Drosophila melanogaster.

Naringenin, the predominant bioflavonoid found in grapefruit and tomato has diverse bioactive properties that encompass anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-estrogenic, anti-hyperlipidemic and anti-hyperglycemic characteristics. Naringenin has not been explored for its pro-longevity traits in fruit flies. Therefore, the current study explores its influence on longevity, fecundity, feeding rate, larval development, resistance to starvation stress and body weight in male and female wild-type Drosophila melanogaster Canton-S flies. Flies were fed with normal and high fat diets respectively. The results implied hormetic effects of naringenin on longevity and development in flies. In flies fed with standard and high fat diets, lower concentrations of naringenin (200 and 400 µM) augmented mean lifespan while higher concentrations (600 and 800 µM) were consistently lethal. However, enhanced longevity seen at 400 µM of naringenin was at the expense of reduced fecundity and food intake in flies. Larvae reared on standard diet having 200 µM of naringenin exhibited elevated pupation and emergence as flies. Eclosion time was hastened in larvae reared on standard diet having 200 µM of naringenin. Female flies fed with a standard diet having 200 and 400 µM of naringenin were more resistant to starvation stress. Reduction in body weight was observed in male and female flies fed with a high fat diet supplemented with 200 and 400 µM of naringenin respectively. Collectively, the results elucidated a context- and dose-dependent hormetic efficacy of naringenin that varied with gender, diet and stage of lifecycle in flies.

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster.

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F2 and F3 generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.