Gain-of-Function Mutations of Receptor Tyrosine Kinases in Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in human gastrointestinal tract. We first found that most GISTs expressed KIT, a receptor tyrosine kinase encoded by protooncogene c-kit and that approximately 90% of the sporadic GISTs had somatic gain-of-function mutations of the c-kit gene. Since both GISTs and interstitial cells of Cajal (ICCs) were double-positive for KIT and CD34, GISTs were considered to originate from ICCs or their precursor cells. We also found that germline gain-of-function mutations of the c-kit gene resulted in familial and multiple GISTs with diffuse hyperplasia of ICCs as the preexisting lesion. Moreover, we found that about half of the sporadic GISTs without c-kit gene mutations had gain-of-function mutations of platelet-derived growth factor receptor alpha (PDGFRA) gene that encodes another receptor tyrosine kinase. Imatinib which is known to inhibit constitutively activated BCR-ABL tyrosine kinase in chronic myelogenous leukemia also inhibits constitutive activation of mutated KIT and PDGFRA, and is now being used for metastatic or unresectable GISTs as a molecular target drug. Mutational analyses of c-kit and PDGFRA genes are considered to be significant for prediction of effectiveness of imatinib and newly developed/developing other agents on GISTs. Some mouse models of familial and multiple GISTs have been genetically created, and may be useful for further investigation of GIST biology.

KIT and PDGFRA mutations of gastrointestinal stromal tumor

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Background: KIT or PDGFRA mutations are found in gastrointestinal stromal tumors (GIST) and are correlated with imatinib (IM) effects. Most reports studied only hot-spots of each gene using paraffin sections and extracted DNA. Here we examined full sequence of the genes using frozen section of GI mesenchymal tumors. Methods: Histologic Dx was done with HE and immunohistochemistory (IH). Using RNA obtained from fresh samples of serial 209 pts with GIST (n=174), myogenic (21), neurogenic tumors (11), or GI sarcoma (3), KIT or PDGFRA cDNA was amplified by RT-PCR and fully sequenced. Results: Tumors other than GIST showed no KIT-immunoreactivity, and had no-PCR-products of KIT (32) or wild type (WT) (3). PDGFRA of these tumors is WT. In IH, KIT was positive in 94% of GIST and CD34 in 84%. 7 GIST showed no-PCR-products of KIT, 8 WT of the genes, 142 KIT, or 17 PDGFRA mutations. Mutations are mutually exclusive. No-PCR was associated with IM-responded GIST (6 out of 15 IM-treated pts), in which KIT expression in IH was scarcely seen. WT are found in 3 juvenile GIST or 4 NF-1, and only 1 adult GIST showed WT. KIT mutations are found in exon (Ex) 9 (10 pts), Ex 11 (125), Ex 13 (3), or Ex 17 (4). All Ex 9 mutations are typical insertion mutations, found in small intestine (8) or colon (2), and associated with poor prognosis. Ex 13 and 17 mutations are missense and Ex 11 showed various type of mutations including deletion, insertion and missense mutations. These mutations distributed throughout GI tract. Deletion mutations in Ex 11 are associated with high recurrence rates (38/64 pts) and poor prognosis. 7 pts showed insertion mutation in the distal part of Ex 11. PDGFRA mutations found in Ex 12 (4 pts) or Ex18 (13) are missense mutations and associated with gastric location, epithelioid histology (10/16), low mitotic activity and relatively indolent clinical features. Conclusions: KIT mRNA and protein are sometimes depressed in IM-responded lesions, which causes difficulty in mutation research. Mutations in KIT and PDGFRA are specific for GIST and WT GIST is extremely rare in adult pts except NF-1.

No significant financial relationships to disclose.

Neoadjuvant transarterial chemoembolization (TACE) using cisplatin with the combination of dose-dense intravenous administration of paclitaxel for the locally advanced cervical adenocarcinoma

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Background: Adenocarcinoma (including adenosquamous carcinoma) of the uterine cervix has a tendency to early lymph node metastasis and is resistant to radiation therapy, thus results in poor prognosis compared with squamous cell carcinoma. Neoadjuvant chemotherapy (NAC) followed by radical hysterectomy (RH) for bulky cervical adenocarcinoma seems to be an alternative therapy to primary radiation. Methods: P2 at the single institution. Eligible criteria were as follows: Histologically diagnosed cervical adeno or adenosquamous carcinoma with FIGO stage IB2-IVA, Age < or equal to 75, PS 0–2, given informed consent. The NAC regimen consisted of paclitaxel (60mg/m2, iv, D1, D8, D15) and cisplatin (70 mg/m2, trans-uterine arterial infusion followed by embolization using the gelform, D2) repeated every 3 weeks for 2–3 cycles, followed by RH. Primary endpoints were clinical and pathological responses, and secondary endpoints were toxicities, relapse free survival (RFS) and overall survival (OS). Results: Enrolled patients: 22 (1998–2006), Age: median 51 (33–75), FIGO stage: IB2 (9), IIA-IIB (8), IIIB (3), IVA (2), adeno/adenosquamous: 16/6. Toxicities during NAC (CTCAE ver.3) were as follows: G3/G4 neutropenia 18% (4/22), G3/G4 anemia 14% (3/22), G3/G4 thrombocytopenia 0%, G2/G3 sensory neuropathy 0 %, G3/G4 creatinine elevation 0%, G2 alopecia 100%. Clinical response rate (RR: CR+PR) of the patients with stage IB2-IIB was 100%. 16 of 17 received RH, and no residual malignant cells were found pathologically (pCR) in 3. RR of the patients with stage IIIb-IVa was 80%, three patients completed RH with either modified anterior or posterior exenteration, and pCR was found in one patient. The rate of radiation therapy following either NAC or surgery among enrolled patients were 18% (3/17) with stage IB2-IIB and 40% (2/5) with IIIB-IVA. 5 year RFS/OS were 69%/68% with stage IB2-IIb and 60%/60% with stage IIIb-IVa. All 15 alive patients had RH. One patient with stage IVa had urostomy, and other 14 patients have no trouble in urination function. Conclusions: TACE with cisplatin and dose dense paclitaxel in the neoadjuvant setting is feasible and effective for cervical adenocarcinoma.

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Validation of genotyping of gastrointestinal stromal tumor in Japan

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Background: Most gastrointestinal stromal tumors (GIST) have activating mutations in the KIT or PDGFRA gene. Genotyping of GIST is important in Dx and Tx of GIST. Methods of genotyping using genomic DNA extracted from paraffin-embedded specimens are diverse and not standardized. We did validation study of genotyping using special reference to sequencing data obtained from cDNA from fresh GIST samples. Methods: Three DNA extraction methods (QIAamp, DEXPAT, or original) and four PCR methods (Ex Taq, AmpliTaq condition-1, AmpliTaq condition-2, or QIAGEN Tag) were compared using 20 paraffin-embedded specimens with special reference to sequencing data obtained from cDNA from corresponding 20 fresh GIST samples. After DNA extraction, KIT exon 9, 11, 13 and 17, and PDGFRA exon 12 and 18 were amplified by each PCR method using specific primers and directly sequenced. Results: In evaluation of PCR method, the protocol with Ex Taq showed 100% amplication of DNA and sequence agreement, the protocol with QIAGEN Tag 99%, and the protocol with AmpliTaq condition-2 86% agreement, and the protocol with AmpliTaq condition-1 showed much less amplication and higher disagreement. For the DNA extraction, the protocol with QIAamp showed best DNA extraction and its DNA sequence data were consistent with reference sequence in 98%, DNA sequence obtained using DEXPAT showed 33% consistency, and 89% of DNA sequence data obtained from an original method was agreed with reference data. Some modifications improved DNA amplication but inconsistent sequence data also increased probably due to miss-PCR. Conclusions: Each DNA extraction method had different quantity of DNA and four PCR methods showed different quality. Using this validation study, a standard genotyping method in Japan was established.

No significant financial relationships to disclose.

The expression profile of functional regulatory T cells, CD4+CD25high+/forkhead box protein P3+, in patients with ulcerative colitis during active and quiescent disease

Regulatory T cells (T(reg)) have an essential role in maintaining immune tolerance in the gut. The functional CD4(+) T(reg) express the transcription factor forkhead box protein 3 (FoxP3) or a CD25(high) in humans. Further, depletion of elevated granulocytes/monocytes by extracorporeal adsorption (GMA) induces immunomodulation in patients with ulcerative colitis (UC). We investigated the impact of GMA on T(reg). Thirty-one UC patients, clinical activity index (CAI) 12.1 +/- 2.97, refractory to conventional medications including intravenous corticosteroid and 13 healthy controls (HC), were included. Patients received five GMA sessions over 5 weeks. Biopsies from the rectal mucosa and blood samples at baseline and post-GMA were immunostained with anti-CD4/FoxP3 and anti-CD4/CD25 antibodies for immunohistochemistry and flow cytometry. Following GMA, 22 of 31 patients achieved remission (CAI <or= 4, P < 0.01) and their endoscopic activity index decreased from 10.6 +/- 2.32 to 4.75 +/- 1.48 (P = 0.003). The circulating CD4(+)CD25(high+) T(reg) level was low and increased markedly in responders (P < 0.02). In the nine non-responders, the baseline CD4(+)CD25(high+) T(reg) level was about 50% of the level in the responders (P < 0.03) or in the HC (P < 0.01), and all nine had to undergo colectomy. Conversely, the number of CD4(+)/FoxP3(+) mucosal T(reg) in GMA responders decreased significantly after the fifth GMA session compared with the baseline level (P < 0.05). It is believed that the CD4(+) T(reg) has an essential role in the control of immune pathology in UC patients and a net influx of these cells from the circulation into the mucosa may proceed to suppress inflammation. GMA can impact the circulating as well as the mucosal levels of T(reg).

PGE2-receptor subtype EP4-dependent adherence of mastocytoma P-815 cells to matrix components in subcutaneous tissues overlaying inside surface of air pouch cavity in CDF1 mouse

OBJECTIVES

It remains to be fully clarified how adhesion of mast cells is regulated in vivo. We previously reported that PGE2-receptor EP4 stimulated the adhesion of mouse mastocytoma P-815 cells to plate-bound fibronectin. Our purpose in this study is to evaluate the adhesion using a system, which can mimic the in vivo adhesion.

METHODS

P-815 cells were transplanted in an air pouch produced in the transplantable mice, CDF1. The number of cells that adhere to the subcutaneous tissues overlaying the inside cavity surface was determined.

RESULTS

The number of adhered cells was decreased in mice administered with ibuprofen or an EP4 antagonist, ONO AE3-208. A local administration of PGE(2) or a phorbol ester, PMA, increased the number of adhered cells, which was also suppressed in the mice treated with ONO AE3-208.

CONCLUSION

Our results suggest that PGE(2)-mediated adhesion of P-815 cells in the subcutaneous tissues of the air pouch is mediated by the EP4 subtype.

A mouse model of a human multiple GIST family with KIT-Asp820Tyr mutation generated by a knock-in strategy

Several families exhibiting multiple gastrointestinal stromal tumours (GISTs) and germline c-kit gene mutations at exons 8, 11, 13, or 17 have been reported. These patients also exhibit diffuse hyperplasia of the interstitial cells of Cajal (ICCs) as a pre-existing lesion of multiple GISTs. We generated a mouse model of a family with germline c-kit gene mutation at exon 17, and compared the phenotypes between the mice and humans. The mouse counterpart (KIT-Asp818Tyr) of the human KIT-Asp820Tyr mutation was transmitted into germline by a knock-in strategy. Mating of male and female heterozygotes (KIT-Asp818Tyr/+) resulted in the generation of homozygotes (KIT-Asp818Tyr/KIT-Asp818Tyr). Histological examination revealed that all heterozygotes had both a small KIT-positive mesenchymal tumour at the caecum, consistent with GIST, and KIT-positive diffuse spindle-shaped cell proliferation in the distal oesophagus, stomach, proximal duodenum, and colon consistent with ICC hyperplasia. All homozygotes exhibited a larger caecal tumour and more prominent spindle-shaped cell proliferation compared with the heterozygous mice, and they usually died within 10 weeks after birth, likely due to ileus. The small intestine of both genotypes showed no apparent morphological abnormality, and autonomous contraction of the ileal segments appeared normal. Western blotting demonstrated that the caecal tumours expressed phosphorylated KIT, MAPK, Stat1, and Stat5. These mutant mice are considered to be useful for further investigation of the mechanism of GIST development as a result of ICC hyperplasia and for assessment of the in vivo effects of drugs against molecular targets.

Ionic mechanisms and Ca2+ handling in airway smooth muscle

Asthma is a disease characterised by reversible contraction of airway smooth muscle. Many signalling pathways are now known to underlie that contraction, almost all of which revolve around Ca(2+) handling. Ca(2+) homeostasis in turn is governed by a wide variety of ionic mechanisms, which are still poorly understood. The present review will briefly summarise those mechanisms that have been recognised for decades, but will then devote considerable attention to several novel ionic signalling mechanisms such as capacitative Ca(2+) entry, the reverse mode of the Na(+)/Ca(2+) exchanger, the role of Cl(-) channels in the release of internal Ca(2+) and that of ryanodine receptors in the refilling of the sarcoplasmic reticulum, as well as the regulation of the monomeric G-protein Rho by ionic mechanisms. Lastly, evidence will be provided that Ca(2+)-dependent contraction may be driven by spatial and temporal heterogeneities in the intracellular Ca(2+) concentration (i.e. Ca(2+) waves/oscillations) rather than by an increase in the global steady state intracellular Ca(2+) concentration.