Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA, 02114, USA.
Laboratory of Radiobiology and Experimental Radiooncology, Clinic of Radiotherapy and Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Sci Rep. 2021 Feb 11;11(1):3656. doi: 10.1038/s41598-021-83142-y.
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.
突变型 KRAS 是一种常见的肿瘤驱动基因，常导致对癌症治疗（如放疗）的耐药。这些肿瘤中的 DNA 复制应激可能构成治疗负担，但目前了解甚少。在这里，我们使用单分子 DNA 纤维分析，首先在一组未受干扰的同基因和非同基因癌细胞系中对基线复制应激进行了特征描述。与观察到的增强的复制应激相关，我们发现与野生型细胞相比，KRAS 突变型细胞中的细胞质双链 DNA 水平增加。然而，尽管存在这种表型，复制应激诱导剂未能选择性地影响 KRAS 突变型细胞，这些细胞受到 CHK1 的保护。同样，研究的大多数外源性应激源未能在 KRAS 突变型细胞中与野生型细胞相比差异地增加细胞质 DNA 积累。然而，我们发现质子辐射能够减缓叉进展，并优先诱导 KRAS 突变型细胞中的叉停滞。质子处理还部分逆转了与 KRAS 突变相关的放射抗性。在存在 KRAS 突变的情况下，质子对细胞的影响与其他影响复制的药物明显不同，突出了质子引起的潜在 DNA 损伤的独特性质。总之，我们的研究结果为与 KRAS 突变相关的复制应激反应提供了深入了解，这可能最终为新的治疗机会提供了依据。
