Israel Medical Association Journal

Background: Biallelic BLM gene mutation carriers are at an increased risk for cancer, including colorectal cancer (CRC). Whether heterozygous BLM gene mutations confer an increased cancer risk remains controversial.

Objectives: To evaluate CRC and endometrial cancer risk in BLM heterozygous mutation carriers.

Methods: Jewish Ashkenazim at high risk for colon or endometrial cancer and endometrial cancer cases unselected for family history were genotyped for the BLM^Ash predominant mutation.

Results: Overall, 243 high-risk individuals were included: 97 men CRC patients (55.12 ± 12.3 years at diagnosis), 109 women with CRC (56.5 ± 13.7 years), 32 women with endometrial cancer (58.25 ± 13.4 years) and 5 women with both CRC and endometrial cancer. In addition, 120 unselected Ashkenazi women with endometrial cancer (64.2 ± 11.58 years) were genotyped. The BLM^Ash mutation was present in 4/243 (1.65%) high-risk patients; 2 CRC (0.97%) 2 endometrial cancer (5.4%), and 1/120 unselected endometrial cancer patients (0.84%). Notably, in high-risk cases, BLM^Ash mutation carriers were diagnosed at a younger age (for CRC 47.5 ± 7.8 years; P = 0.32 ; endometrial cancer 49.5 ± 7.7 years; P = 0.36) compared with non-carriers.

Conclusions: Ashkenazi high risk CRC/endometrial cancer, and women with endometrial cancer have a higher rate of BLM^Ash heterozygous mutation compared with the general population. BLM^Ash heterozygous mutation carriers are diagnosed with CRC and endometrial cancer at a younger age compared with non-carriers. These observations should be validated and the possible clinical implications assessed.

Background: Fanconi anemia complementation group C and Bloom syndrome, rare autosomal recessive disorders marked by chromosome instability, are especially prevalent in the Ashkenazi* Jewish community. A single predominant mutation for each has been reported in Ashkenazi Jews: c.711+4A→T (IVS4 +4 A→T) in FACC[1] and BLM^Ash in Bloom syndrome. Individuals affected by both syndromes are characterized by susceptibility for developing malignancies, and we questioned whether heterozygote carriers have a similarly increased risk.

Objectives: To estimate the cancer rate among FACC and BLM^Ash carriers and their families over three previous generations in unselected Ashkenazi Jewish individuals.

Methods: We studied 42 FACC carriers, 28 BLM^Ash carriers and 43 controls. The control subjects were Ashkenazi Jews participating in our prenatal genetic screening program who tested negative for FACC and BLM^Ash. All subjects filled out a questionnaire regarding their own and a three-generation family history of cancer. The prevalence rates of cancer among relatives of FACC, BLM^Ash and controls were computed and compared using the chi-square test.

Results: In 463 relatives of FACC carriers, 45 malignancies were reported (9.7%) including 10 breast (2.2%) and 13 colon cancers (2.8%). Among 326 relatives of BLM^Ash carriers there were 30 malignancies (9.2%) including 7 breast (2.1%) and 4 colon cancers (1.2%). Controls consisted of 503 family members with 63 reported malignancies (12.5%) including 11 breast (2.2%) and 11 colon cancers (2.2%).

Conclusions: We found no significantly increased prevalence of malignancies among carriers in at least three generations compared to the controls.

Background: The Bloom syndrome gene, BLM, was mapped to 15q26.1 and its product was found to encode a RecQ DNA helicase. The Fanconi anemia complementation group C gene was mapped to chromosome 9q22.3, but its product function is not sufficiently clear. Both are recessive disorders associated with an elevated predisposition to cancer due to genomic instability. A single predominant mutation of each disorder was reported in Ashkenazi Jews: 2281delATCTGAinsTAGATTC for Bloom syndrome (BLM-ASH) and IVS4+4A®T for Fanconi anemia complementation group C.

Objectives: To provide additional verification of the mutation rate of BLM and FACC[1] in unselected Ashkenazi and non-Ashkenazi populations analyzed at the Sheba Medical Center, and to trace the origin of each mutation.

Methods: We used polymerase chain reaction to identify mutations of the relevant genomic fragments, restriction analysis and gel electrophoresis. We then applied the Pronto^TM kit to verify the results in 244 samples and there was an excellent match.

Results: A heterozygote frequency of 1:111 for BLM-ASH and 1:92 for FACC was detected in more than 4,000 participants, none of whom reported a family history of the disorders. The Pronto^TM kit confirmed all heterozygotes. Neither of the mutations was detected in 950 anonymous non-Ashkenazi Jews. The distribution pattern of parental origin differed significantly between the two carrier groups, as well as between each one and the general population.

Conclusions: These findings as well as the absence of the mutations in non-Ashkenazi Jews suggest that: a) the mutations originated in the Israelite population that was exiled from Palestine by the Roman Empire in 70 AD and settled in Europe (Ashkenazi), in contrast to those who remained; and b) the difference in origin distribution of the BS[2] and FACC mutations can be explained by either a secondary migration of a subgroup with a subsequent genetic drift, or a separate geographic region of introduction for each mutation.

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[1] FACC = Fanconi anemia complementation group C