Most GIST patients develop clinical resistance to KIT/PDGFRA tyrosine kinase inhibitors (TKI). However, it is unclear whether clinical resistance results from single or multiple molecular mechanisms in each patient. KIT and PDGFRA mutations were evaluated in 53 GIST metastases obtained from 14 patients who underwent surgical debulking after progression on imatinib or sunitinib. To interrogate possible resistance mechanisms across a broad biological spectrum of GISTs, inter-and intra-lesional heterogeneity of molecular drug-resistance mechanisms were evaluated in the following: conventional KIT (CD117)-positive GISTs with KIT mutations in exon 9, 11 or 13; KIT-negative GISTs; GISTs with unusual morphology; and KIT/PDGFRA wild-type GISTs. Genomic KIT and PDGFRA mutations were characterized systematically, using complementary techniques including D-HPLC for KIT exons 9, 11-18 and PDGFRA exons 12, 14, 18, and mutation-specific PCR (V654A, D820G, N822K, Y823D). Primary KIT oncogenic mutations were found in 11/14 patients (79%). Of these, 9/11 (83%), had secondary drug-resistant KIT mutations, including six (67%) with two to five different secondary mutations in separate metastases, and three (34%) with two secondary KIT mutations in the same metastasis. The secondary mutations clustered in the KIT ATP binding pocket and kinase catalytic regions. FISH analyses revealed KIT amplicons in 2/10 metastases lacking secondary KIT mutations. This study demonstrates extensive intra-and inter-lesional heterogeneity of resistance mutations and gene amplification in patients with clinically progressing GIST. KIT kinase resistance mutations were not found in KIT/PDGFRA wildtype GISTs or in KIT-mutant GISTs showing unusual morphology and/or loss of KIT expression by IHC, indicating that resistance mechanisms are fundamentally different in these tumours. Our observations underscore the heterogeneity of clinical TKI resistance, and highlight the therapeutic challenges involved in salvaging patients after clinical progression on TKI monotherapies.

Homozygosity for the M694V mutation, predominant among North African Jews, is associated with a severe course and prognosis for FMF. This mutation is less common among Arabs and, when present, occurs almost only in heterozygous form. In Arab patients, the disease tends to run a milder course and seems to bear a better prognosis. The phenotype/genotype patterns that are evident from our study of a mixed series of Jewish and Arab children with FMF might provide a rational basis for counseling about the natural history of the disease and for clinical treatment of FMF patients and their families.

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A locus on chromosome 15q26 (IDDM3) produces susceptibility to insulin-dependent diabetes mellitus. Nat Genet 8:189-194 Field LL, Tobias R, Thomson G, Plon S (1996) Susceptibility to insulin-dependent diabetes mellitus maps to a locus (IDDM11) on human chromosome 14q24.3-q31. Genomics 33:1-8

Bilateral breast cancer is traditionally considered an indirect indicator of inherited predisposition to cancer. To appreciate the contribution of genetic determinants to bilateral breast cancer in Jewish women we genotyped 55 such women for the three predominant mutations in BRCA1 (185delAG and 5382insC) and BRCA2 (6174delT) that account for the overwhelming majority of BRCA mutations in high-risk Jewish families. Among women with bilateral breast cancer, 17 mutation carriers (17/55; 29.6%) were identified. Individual mutation frequencies were 18.5% (10/55) for 185delAG, 3.7% (2/55) for 5382insC and 7.4% (5/55) for 6174delT. Carrier rate was significantly higher (P < 0.0016) in women with bilateral breast cancer whose first tumour was diagnosed at or before 42 years of age (82%; 14/17) than in women diagnosed after 42 years of age (7.9%; 3/38). Among patients with bilateral breast cancer and positive family history 45% (14/31) carried a BRCA mutation. Of these 86% (12/14) had one breast cancer diagnosed at or before 42 years of age. Our results suggest that bilateral breast cancer per se, in most cases, does not reflect genetic predisposition, unless associated with early age of onset (first tumour diagnosed at or before 42 years of age). Although the relationship between young age and carrier state in women with bilateral breast cancer is strong, no significant association between family history and carrier state was found. We can thus speculate that women with early onset breast cancer who carry a BRCA1 or BRCA2 mutation are prone to acquire a second breast tumour.