Doxorubicin은 광범위한 암을 치료하는데 사용되는 일반적인 항암제이지만, 내인성 산화질소 생성량과 Doxorubicin의 항암 효과의 상관 관계에 대해서는 아직 명확하게 밝혀지지 않았다. 본 연구에서는 인간 대장암 세포에서 Doxorubicin의 항암 활성에 내인성 산화질소가 미치는 영향을 확인하고자 하였다. HCT116 (p53-WT)과 HT29 (p53-MUT) 세포에서 Doxorubicin 처리에 의해 세포 생존율의 차이를 보였으며, NMA 병행처리는 Doxorubicin의 효과를 감소시켰음을 확인할 수 있었다. 추가 연구를 통해 HCT116과 HT29 세포에서 sub-$G_1$ 기의 세포 빈도와 DNA 단편화의 결과를 통해 내인성 산화질소가 Doxorubicin에 의한 apoptosis를 조절하는 것을 확인하였다. 이러한 결과는 인간 대장암 세포에서 내인성 산화질소와 IAP 발현, p53의 상태에 따른 조절이 Doxorubicin에 의해 유도된다는 것을 보여주며, 이러한 메커니즘은 대장암에서 화학요법의 효율을 향상시키기 위한 전략적인 표적으로 이용할 수 있을 것으로 생각된다.
Doxorubicin is a general chemotherapy drug widely used for a number of cancers. However, the correlation between endogenous nitric oxide ($NO^{ullet}$) levels and chemoresistance to doxorubicin remains unclear. In this study, we investigated the effect of endogenous $NO^{ullet}$ on the anticancer activity of doxorubicin in human colon cancer cell lines HCT116 and HT29 with different p53 status. The cells were treated with either doxorubicin alone or in combination with the $NO^{ullet}$ synthase (NOS) inhibitor $N^G$-monomethyl-L-arginine (NMA). Doxorubicin differentially inhibited the growth of both the HCT116 (p53-WT) and HT29 (p53-MUT) cells, which was mitigated by cotreatment with NMA. Further studies revealed that inhibition of endogenous $NO^{ullet}$ mitigated doxorubicin-induced apoptosis in the HCT116 and HT29 cells, as evidenced by apoptotic DNA fragmentation and the sub-G1 peak of apoptotic markers. Apoptosis was delayed in the HT29 cells, and its magnitude was greatly reduced, underscoring the importance of the modulation of p53 in the response. RT-PCR analysis revealed that doxorubicin down-regulated levels of inhibitors of the apoptosis family (cellular IAP-1 and-2). Collectively, these data show that induction of apoptosis by doxorubicin in human colon cancer cells is possibly related to modulation of endogenous $NO^{ullet}$, the expression of the IAP family of genes, and the status of p53. The underlying mechanisms may represent potential targets for adjuvant strategies to improve the efficacy of chemotherapy for colon cancer.
