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Immunoglobulin light chain amyloidosis is a lethal hematologic disorder driven by clonal plasma cells producing abnormal light chains that damage healthy tissues. Fraser et al. show that BH3 mimetics, which inhibit pro-survival proteins BCL-2 or MCL-1, can effectively eliminate diseased cells.

Abstract Mutant KRAS is a common tumor driver and frequently confers resistance to anti-cancer treatments such as radiation. DNA replication stress in these tumors may constitute a therapeutic liability but is poorly understood. Here, using single-molecule DNA fiber analysis, we first characterized baseline replication stress in a panel of unperturbed isogenic and non-isogenic cancer cell lines. Correlating with the observed enhanced replication stress we found increased levels of cytosolic double-stranded DNA in KRAS mutant compared to wild-type cells. Yet, despite this phenotype replication stress-inducing agents failed to selectively impact KRAS mutant cells, which were protected by CHK1. Similarly, most exogenous stressors studied did not differentially augment cytosolic DNA accumulation in KRAS mutant compared to wild-type cells. However, we found that proton radiation was able to slow fork progression and preferentially induce fork stalling in KRAS mutant cells. Proton treatment also partly reversed the radioresistance associated with mutant KRAS. The cellular effects of protons in the presence of KRAS mutation clearly contrasted that of other drugs affecting replication, highlighting the unique nature of the underlying DNA damage caused by protons. Taken together, our findings provide insight into the replication stress response associated with mutated KRAS, which may ultimately yield novel therapeutic opportunities.

The treatment of ROS1-rearranged non-small cell lung cancer with the TKI crizotinib is limited due to the emergence of resistance. Here, the authors develop a new ROS1/NTRK inhibitor, DS-6051b, which overcomes crizotinib resistance in preclinical models.