Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
Int J Radiat Oncol Biol Phys. 2012 Sep 1;84(1):257-65. doi: 10.1016/j.ijrobp.2011.10.064. Epub 2012 Jan 26.
Patients treated with radiotherapy for head-and-neck cancer invariably suffer its deleterious side effect, xerostomia. Salivary hypofunction ensuing from the irreversible destruction of glands is the most common and debilitating oral complication affecting patients undergoing regional radiotherapy. Given that the current management of xerostomia is palliative and ineffective, efforts are now directed toward preventive measures to preserve gland function. The human homolog of Tousled protein, TLK1B, facilitates chromatin remodeling at DNA repair sites and improves cell survival against ionizing radiation (IR). Therefore, we wanted to determine whether a direct transfer of TLK1B protein to rat salivary glands could protect against IR-induced salivary hypofunction.
The cell-permeable TAT-TLK1B fusion protein was generated. Rat acinar cell line and rat salivary glands were pretreated with TAT peptide or TAT-TLK1B before IR. The acinar cell survival in vitro and salivary function in vivo were assessed after radiation.
We demonstrated that rat acinar cells transduced with TAT-TLK1B were more resistant to radiation (D₀ = 4.13 ± 1.0 Gy; α/β = 0 Gy) compared with cells transduced with the TAT peptide (D₀ = 4.91 ± 1.0 Gy; α/β = 20.2 Gy). Correspondingly, retroductal instillation of TAT-TLK1B in rat submandibular glands better preserved salivary flow after IR (89%) compared with animals pretreated with Opti-MEM or TAT peptide (31% and 39%, respectively; p < 0.01).
The results demonstrate that a direct transfer of TLK1B protein to the salivary glands effectively attenuates radiation-mediated gland dysfunction. Prophylactic TLK1B-protein therapy could benefit patients undergoing radiotherapy for head-and-neck cancer.
接受头颈部癌症放射治疗的患者无一例外地遭受其有害副作用——口干症。腺体不可逆破坏导致的唾液功能低下是影响接受区域放射治疗的患者最常见和最虚弱的口腔并发症。鉴于目前对口干症的治疗是姑息性和无效的，因此现在努力采取预防措施来保护腺体功能。Tousled 蛋白的人类同源物 TLK1B 可促进 DNA 修复部位的染色质重塑，并提高细胞对电离辐射 (IR) 的存活率。因此，我们想确定将 TLK1B 蛋白直接转移到大鼠唾液腺是否可以防止 IR 诱导的唾液功能低下。
生成了细胞可渗透的 TAT-TLK1B 融合蛋白。用 TAT 肽或 TAT-TLK1B 预处理大鼠腺细胞系和大鼠唾液腺，然后进行 IR。辐射后评估体外腺细胞存活率和体内唾液功能。
我们证明与转染 TAT 肽的细胞（D₀ = 4.91 ± 1.0 Gy；α/β = 20.2 Gy）相比，转染 TAT-TLK1B 的大鼠腺细胞对辐射更具抵抗力（D₀ = 4.13 ± 1.0 Gy；α/β = 0 Gy）。相应地，与用 Opti-MEM 或 TAT 肽预处理的动物相比（分别为 31%和 39%；p < 0.01），TLK1B 在大鼠颌下腺中的逆行滴注在 IR 后更好地保留了唾液流量。
这些结果表明，TLK1B 蛋白的直接转移到唾液腺可有效减轻辐射介导的腺体功能障碍。预防性 TLK1B-蛋白治疗可能有益于接受头颈部癌症放射治疗的患者。
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