Wei Bih-Rong, Verdi Vincenzo, Zhang Shuling, Mock Beverly A, Shive Heather R, Simpson R Mark
bioRxiv. 2025 Apr 26:2025.04.24.650512. doi: 10.1101/2025.04.24.650512.
BACKGROUND/OBJECTIVE: Mucosal melanoma (MM) is a poorly responsive, rare and aggressive subtype with paucity of targetable recurrent driver mutations, although Ras/MAPK and PI3K/AKT/mTOR signaling pathway activations are common. Eventual tumor evasion of targeted therapy continues to limit treatment success. Adequate models are necessary to address therapeutic resistance. The relatively greater incidence of naturally occurring MM in dogs, as well as its comparable clinical and pathological characteristics to human MM, represents a promising opportunity for predictive patient modeling. Resistance-promoting crosstalk between Ras/MAPK and PI3K/AKT/mTOR signaling under trametinib inhibition of MEK was studied in a canine MM model. Emphasis was placed on the suppressive effect of trametinib on cell cycle entry and its potential role in drug resistance.
D-type cyclins were investigated using five MM cell lines exhibiting differential sensitivities to trametinib. Drug-treated cells were analyzed for signaling pathway activation, proliferation, survival, cell death, and cell cycle in the context of D-type cyclin expression. Cyclin D2 expression was manipulated using siRNA knock down or inducible recombinant overexpression.
With diminished cyclin D1 under trametinib treatment, relatively trametinib-resistant MM cells exhibited capacity to upregulate cyclin D2, which promoted proliferation, whereas sensitive cells did not similarly respond. Inhibition of the compensatory cyclin D2 response restored sensitivity to resistant cells. Induced cyclin D2 overexpression promoted survival to otherwise trametinib-sensitive MM cells that did not exhibit capacity to upregulate endogenous cyclin D2. PI3K/AKT/mTOR signaling upregulation under trametinib was suppressed by mTORC1/2 inhibition, which similarly diminished cyclin D2 response.
The compensatory switch from preferential reliance on cyclin D1 to D2 appears to play a role in MM resistance to MEK inhibition.
背景/目的：黏膜黑色素瘤（MM）是一种反应性差、罕见且侵袭性强的亚型，尽管Ras/MAPK和PI3K/AKT/mTOR信号通路激活较为常见，但可靶向的复发性驱动突变却很少。最终肿瘤对靶向治疗的逃避继续限制治疗的成功。需要适当的模型来解决治疗耐药性问题。犬类中自然发生的MM发病率相对较高，以及其与人类MM具有相似的临床和病理特征，为预测性患者建模提供了一个有前景的机会。在犬类MM模型中研究了曲美替尼抑制MEK时Ras/MAPK和PI3K/AKT/mTOR信号之间促进耐药的串扰。重点关注曲美替尼对细胞周期进入的抑制作用及其在耐药性中的潜在作用。
使用对曲美替尼表现出不同敏感性的五种MM细胞系研究D型细胞周期蛋白。在D型细胞周期蛋白表达的背景下，分析药物处理的细胞的信号通路激活、增殖、存活、细胞死亡和细胞周期。使用小干扰RNA敲低或诱导性重组过表达来操纵细胞周期蛋白D2的表达。
在曲美替尼治疗下细胞周期蛋白D1减少时，相对曲美替尼耐药的MM细胞表现出上调细胞周期蛋白D2的能力，这促进了增殖，而敏感细胞则没有类似反应。抑制代偿性细胞周期蛋白D2反应可恢复耐药细胞的敏感性。诱导细胞周期蛋白D2过表达可促进原本对曲美替尼敏感但不具有上调内源性细胞周期蛋白D2能力的MM细胞存活。曲美替尼作用下PI3K/AKT/mTOR信号上调被mTORC1/2抑制所抑制，这同样减少了细胞周期蛋白D2反应。
从优先依赖细胞周期蛋白D1到D2的代偿性转变似乎在MM对MEK抑制的耐药性中起作用。
