Lee Daniel J, Maseyesva Brett, Westra William, Long Donlin, Niparko John K, Califano Joseph
Department of Otolaryngology, UMass Memorial Medical Center, Worcester, MA 01655, USA.
Otol Neurotol. 2006 Feb;27(2):213-9. doi: 10.1097/01.mao.0000199753.44191.73.
Genetic and immunohistochemical studies may provide insight into the mechanisms of vestibular schwannoma (VS) recurrence following radiation therapy.
Stereotactic radiation therapy is an increasingly common alternative to microsurgical resection for the primary management of sporadic VS. The molecular mechanisms associated with recurrent vestibular schwannoma (VS) following radiation therapy are not known.
Primary or irradiated VS tumors were fresh-frozen at the time of surgical resection and microdissected to undergo DNA extraction. Lymphocytic control DNA was isolated from blood obtained by venipuncture. Paired normal and tumor DNA specimens were analyzed for allelic loss by PCR amplification of polymorphic dinucleotide repeat sequences. Immunohistochemical studies were performed on paraffin-embedded, irradiated surgical specimens.
Using 16 polymorphic microsatellite markers, 20 of 26 non-irradiated VS demonstrated loss of heterozygosity (LOH) in at least one locus of chromosome 22q. In contrast, none of the four irradiated recurrent VS demonstrated LOH on chromosome 22q (p = 0.008). No allelic loss was seen in either the primary or irradiated VS utilizing markers mapping to chromosome 10. Deletions on chromosome 10 are seen in both benign and higher-grade meningiomas and intracranial malignancies associated with radiotherapy. Immunohistochemical studies were performed to detect the protein product of the NF2 gene, merlin, in the four irradiated VS. NF2 staining was not observed.
This study represents the first microsatellite and immunohistochemical analysis of recurrent VS following radiation therapy. Our preliminary observations suggest an alternative mechanism of NF2 inactivation that may correlate with radioresistance in VS.
基因和免疫组织化学研究可能有助于深入了解放射治疗后前庭神经鞘瘤（VS）复发的机制。
立体定向放射治疗作为散发性VS初始治疗的一种替代方法，正越来越普遍。放射治疗后复发性前庭神经鞘瘤（VS）相关的分子机制尚不清楚。
在手术切除时将原发性或接受过放射治疗的VS肿瘤新鲜冷冻，并进行显微切割以提取DNA。从静脉穿刺采集的血液中分离淋巴细胞对照DNA。通过对多态性二核苷酸重复序列进行PCR扩增，分析配对的正常和肿瘤DNA标本的等位基因缺失情况。对石蜡包埋的放射治疗手术标本进行免疫组织化学研究。
使用16个多态性微卫星标记，26例未接受放射治疗的VS中有20例在22号染色体的至少一个位点表现出杂合性缺失（LOH）。相比之下，4例接受放射治疗的复发性VS在22号染色体上均未表现出LOH（p = 0.008）。利用定位到10号染色体的标记，在原发性或接受过放射治疗的VS中均未观察到等位基因缺失。在良性和高级别脑膜瘤以及与放射治疗相关的颅内恶性肿瘤中均可见10号染色体缺失。对4例接受放射治疗的VS进行免疫组织化学研究以检测NF2基因的蛋白产物merlin。未观察到NF2染色。
本研究是首次对放射治疗后复发性VS进行微卫星和免疫组织化学分析。我们的初步观察结果提示了一种NF2失活的替代机制，这可能与VS的放射抗性相关。
