Abstract
Cisplatin is a platinum-based drug that is used for the treatment of a wide-variety of primary human cancers. However, the therapeutic efficacy of cisplatin is often limited by intrinsic or acquired drug resistance. An important goal, therefore, is to identify mechanisms that lead to cisplatin resistance in cancer, and then use this information to more effectively target resistant cells. Cisplatin-resistant clones of the HCT116 cell line underwent a prolonged G2 arrest after cisplatin treatment while sensitive clones did not. The staurosporine analog UCN-01 abrogated this G2 arrest and sensitized the resistant clones to cisplatin. At later time points, 4N arrested cells assumed a tetraploid G1 state that was characterized by depletion of Cyclin A, Cyclin B, and CDC2, and increased expression of p53 and p21, in 4N cells. siRNA-mediated knockdown of p21 abrogated the tetraploid G1 arrest and induced killing that was dependent on p53. The results identify two targetable 4N arrests that can contribute to cisplatin resistance: First, a prolonged G2 arrest that can be targeted by UCN-01, and second, a tetraploid G1 arrest that can be targeted by siRNA against p21.
Highlights
Cisplatin (CP) is a platinum-based drug that is widely used in the treatment of various primary human cancers
These findings identify two targetable 4N arrests that can contribute to cisplatin resistance: First, a prolonged G2 arrest that can be targeted by UCN-01, and second, a tetraploid G1 arrest that can be targeted by siRNA against p21
The results suggest HCT116 contains a mixture of clones that vary widely in their sensitivity to CP
Summary
Cisplatin (CP) is a platinum-based drug that is widely used in the treatment of various primary human cancers. CP induces DNA intra-strand and inter-strand crosslinks that can trigger cell cycle arrest, DNA repair, and/or apoptotic death [1]. CP has shown clinical efficacy against different cancer types, including testicular, ovarian, and head and neck cancer [1]. The development of CP resistance remains a major obstacle to its clinical use. While tumors may show an initial killing response to CP and effectively be ‘‘cured’’, they can often grow back in a form that is both therapy resistant and highly aggressive. It is important to identify the molecular mechanisms that lead to CP resistance in cancer, and use this information to target resistant cells
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