MYB Promotes Desmoplasia in Pancreatic Cancer through Direct Transcriptional Up-regulation and Cooperative Action of Sonic Hedgehog and Adrenomedullin
MYB Promotes Desmoplasia in Pancreatic Cancer through Direct Transcriptional Up-regulation and Cooperative Action of Sonic Hedgehog and Adrenomedullin
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DOI：
10.1074/jbc.m116.732651
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发表时间：
2016-07-29
影响因子：
4.8
通讯作者：
Singh, Ajay P.
中科院分区：
文献类型：
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作者：
Bhardwaj, Arun;Srivastava, Sanjeev K.;Singh, Ajay P.
广泛的结缔组织增生是胰腺癌（PC）的一个突出的病理特征，它不仅影响肿瘤的发展，而且还影响治疗结果。最近，我们证明了 MYB（一种致癌转录因子）在 PC 生长和转移中的新作用。在这里，我们研究了它对胰腺肿瘤组织病理学的影响以及相关的分子和生物学机制。与源自 MYB 沉默的 PC 细胞的肿瘤异种移植物相比，源自原位接种 MYB 过表达 PC 细胞的肿瘤异种移植物在组织学分析中表现出更大的结缔组织形成。这些发现通过使用 I 型胶原、纤连蛋白（主要细胞外基质蛋白）和 α-SMA（肌成纤维细胞或活化的胰腺星状细胞 (PSC) 的良好表征标记）对肿瘤异种移植切片进行免疫染色得到了进一步证实。同样，与 MYB 沉默的细胞相比，MYB 过表达的 PC 细胞在共培养系统中为 PSC 提供了显着更大的生长益处。通过对 MYB 过表达与沉默 PC 细胞的深度测序数据进行分析，发现 Sonic-hedgehog (SHH) 和 Adrenomedullin (ADM) 是两个差异表达基因，它们编码参与肿瘤间质串扰的分泌配体。计算机分析预测了 SHH 和 ADM 启动子中假定的 MYB 结合位点，后来通过染色质免疫沉淀证实了这一点。通过使用SHH和ADM的特异性抑制剂和外源重组蛋白的共培养，证实了SHH和ADM在促进PSC生长中的协同作用。重要的是，虽然 SHH 仅以旁分泌方式作用于 PSC，并且仅间接影响 PC 细胞的生长，但 ADM 可以直接影响 PC 细胞和 PSC 的生长。总之，我们确定 MYB 是胰腺肿瘤结缔组织形成的新型调节剂，这表明它在 PC 病理学中具有多种作用。
Extensive desmoplasia is a prominent pathological characteristic of pancreatic cancer (PC) that not only impacts tumor development, but therapeutic outcome as well. Recently, we demonstrated a novel role of MYB, an oncogenic transcription factor, in PC growth and metastasis. Here we studied its effect on pancreatic tumor histopathology and associated molecular and biological mechanisms. Tumor-xenografts derived from orthotopic-inoculation of MYB-overexpressing PC cells exhibited far-greater desmoplasia in histological analyses compared with those derived from MYB-silenced PC cells. These findings were further confirmed by immunostaining of tumor-xenograft sections with collagen-I, fibronectin (major extracellular-matrix proteins), and alpha-SMA (well-characterized marker of myofibroblasts or activated pancreatic stellate cells (PSCs)). Likewise, MYB-overexpressing PC cells provided significantly greater growth benefit to PSCs in a co-culture system as compared with the MYB-silenced cells. Interrogation of deep-sequencing data from MYB-overexpressing versus-silenced PC cells identified Sonic-hedgehog (SHH) and Adrenomedullin (ADM) as two differentially-expressed genes among others, which encode for secretory ligands involved in tumor-stromal cross-talk. In-silico analyses predicted putative MYB-binding sites in SHH and ADM promoters, which was later confirmed by chromatin-immunoprecipitation. A cooperative role of SHH and ADM in growth promotion of PSCs was confirmed in co-culture by using their specific-inhibitors and exogenous recombinant-proteins. Importantly, while SHH acted exclusively in a paracrine fashion on PSCs and influenced the growth of PC cells only indirectly, ADM could directly impact the growth of both PC cells and PSCs. In summary, we identified MYB as novel regulator of pancreatic tumor desmoplasia, which is suggestive of its diverse roles in PC pathobiology.