Department of Research, Advanced Diagnostics, and Technological Innovation, Translational Research Area, Regina Elena National Cancer Institute, Rome, Italy.
Department of Medical, Oral and Biotechnological Sciences, Tumor Biology Section, University "G. d'Annunzio", Via de Vestini, 31, 66013, Chieti, Italy.
J Exp Clin Cancer Res. 2017 Sep 11;36(1):126. doi: 10.1186/s13046-017-0596-z.
As an important cellular stress sensor phosphoprotein p53 can trigger cell cycle arrest and apoptosis and regulate autophagy. The p53 activity mainly depends on its transactivating function, however, how p53 can select one or another biological outcome is still a matter of profound studies. Our previous findings indicate that switching cancer cells in high glucose (HG) impairs p53 apoptotic function and the transcription of target gene PUMA.
Here we report that, in response to drug adriamycin (ADR) in HG, p53 efficiently induced the expression of DRAM (damage-regulated autophagy modulator), a p53 target gene and a stress-induced regulator of autophagy. We found that ADR treatment of cancer cells in HG increased autophagy, as displayed by greater LC3II accumulation and p62 degradation compared to ADR-treated cells in low glucose. The increased autophagy in HG was in part dependent on p53-induced DRAM; indeed DRAM knockdown with specific siRNA reversed the expression of the autophagic markers in HG. A similar outcome was achieved by inhibiting p53 transcriptional activity with pifithrin-α. DRAM knockdown restored the ADR-induced cell death in HG to the levels obtained in low glucose. A similar outcome was achieved by inhibition of autophagy with cloroquine (CQ) or with silencing of autophagy gene ATG5. DRAM knockdown or inhibition of autophagy were both able to re-induce PUMA transcription in response to ADR, underlining a reciprocal interplay between PUMA to DRAM to unbalance p53 apoptotic activity in HG. Xenograft tumors transplanted in normoglycemic mice displayed growth delay after ADR treatment compared to those transplanted in diabetics mice and such different in vivo response correlated with PUMA to DRAM gene expression.
Altogether, these findings suggest that in normal/high glucose condition a mutual unbalance between p53-dependent apoptosis (PUMA) and autophagy (DRAM) gene occurred, modifying the ADR-induced cancer cell death in HG both in vitro and in vivo.
作为一种重要的细胞应激感应磷酸化蛋白，p53 可以触发细胞周期停滞和细胞凋亡，并调节自噬。p53 的活性主要取决于其转录激活功能，然而，p53 如何选择一种或另一种生物学结果仍然是一个深入研究的问题。我们之前的研究结果表明，在高糖（HG）环境中切换癌细胞会损害 p53 的凋亡功能和靶基因 PUMA 的转录。
在这里，我们报告说，在 HG 中的阿霉素（ADR）药物反应中，p53 有效地诱导了 DRAM（损伤调节自噬调节剂）的表达，DRAM 是 p53 的一个靶基因，也是应激诱导自噬的调节剂。我们发现，与在低糖中用 ADR 处理的细胞相比，HG 中 ADR 处理的癌细胞中的自噬增加，表现为 LC3II 积累和 p62 降解增加。HG 中增加的自噬部分依赖于 p53 诱导的 DRAM；事实上，用特定的 siRNA 敲低 DRAM 逆转了 HG 中自噬标记物的表达。用 pifithrin-α抑制 p53 转录活性也可达到类似的结果。DRAM 敲低将 HG 中 ADR 诱导的细胞死亡恢复到低糖中获得的水平。用氯喹（CQ）抑制自噬或沉默自噬基因 ATG5 也可达到类似的结果。DRAM 敲低或自噬抑制均可在 ADR 作用下重新诱导 PUMA 转录，这强调了在 HG 中，PUMA 与 DRAM 之间的相互作用导致 p53 凋亡活性失衡。在正常血糖的小鼠中移植的异种移植肿瘤在接受 ADR 治疗后与在糖尿病小鼠中移植的肿瘤相比生长缓慢，这种不同的体内反应与 PUMA 与 DRAM 基因表达相关。
总之，这些发现表明，在正常/高糖条件下，p53 依赖性凋亡（PUMA）和自噬（DRAM）基因之间发生了相互失衡，改变了 HG 中 ADR 诱导的癌细胞死亡，无论是在体外还是在体内。
