<i>Materials and methods</i> We compared DNA methylation of 1,505 selected promoter CpGs in chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL) with and without the Philadelphia chromosome t(9:22), CD34+ hematopoietic stem cells transfected with <i>BCR-ABL</i>, and other tumors without <i>BCR-ABL</i> (acute promyelocytic leukemia (APL) and gastrointestinal stromal tumors (GIST).
Gastrointestinal stromal tumours (GISTs), once assumed to be of smooth muscle origin, generally express CD117 and CD34, similar to the interstitial cells of Cajal.
Gastrointestinal stromal tumor (GIST) is believed to originate from intestinal cells of Cajal or their stem cell precursors, and expresses stemness-related markers, such as CD117, CD34, DOG1 and nestin.
Additional transcripts relevant to GIST biology were also evaluated, including members of the IGF-signaling pathway (IGF1, IGF2, and insulin receptor [INSR]), neural markers (CDH2[CDH: Cadherin], neurofilament, light polypeptide, LHX2 [LHX: LIM homeobox], and KIRREL3 [KIRREL: kin of IRRE like]), KIT, PDGFRA, CD34, and HIF1A.
After imatinib treatment, in both patients, the resected tumors were composed of heterogeneous spindle cells negative to KIT, DOG1, and CD34 IHC staining, which was unusual for GIST.
Although previous studies have shown that the clinical outcome of patients with GIST is associated with mitotic activity, the proliferation index determined by the Ki-67 labeling index, immunophenotype (CD34 and/or p53) and mutation in exon 11 of the c-kit, a definitive discrimination between benign and malignant GIST has not yet been established.
Approximately 70% of GISTs are positive for CD34, 20-30% are positive for smooth muscle actin (SMA), 10% are positive for S100 protein and <5% are positive for desmin.
Because both GIST and ICC are double-positive for KIT and CD34, and because familial and multiple GIST appear to develop from diffuse hyperplasia of ICC, GIST are considered to originate from ICC or their precursor cells.
Co-expression of KIT or CD34, which is also expressed in GIST and ICCs, was demonstrated in 18 (100%) and 16 SMemb-positive tumors (89%), respectively.
Compared with the overall mutation rate (8.7%) of exon 9, GISTs with CD34+SMA+ had > or = 20% probability of harboring an exon 9 mutation, and all GISTs in the small intestine had a probability of 19%.
Fifty-two cases of primary GIST were distinguished from a group of gastrointestinal mesenchymal tumors using a panel of antibodies such as CD117 and CD34 by immunohistochemical SP method.
Fine-needle aspiration biopsy revealed spindle cells with moderate pleomorphism and immunohistochemically reactive to CD117 and CD34 suggestive of GIST, but the clinical picture was unusual for GIST.
Immuhistochemical analysis of CD34 and CD117 was performed on GIST biopsy samples from both siblings, while c-kit mutational analysis was done by PCR and direct sequencing on DNA from peripheral blood leukocytes of all family members and from paraffin-embedded gastric biopsy specimens of affected siblings.
Immunohistochemical analysis of KIT, CD34, vimentin, alpha-smooth muscle actin (SMA), s-100, p53, ki-67, bcl-2 and bax expression was performed on 20 surgically resected GIST.