Re: High frequency of multiple melanomas and breast and pancreas carcinomas in CDKN2A mutation-positive melanoma families

Analysis of the CDKN2A Gene in FAMMM Syndrome Families Reveals Early Age of Onset for Additional Syndromic Cancers

Familial atypical multiple mole melanoma (FAMMM) syndrome is a hereditary cancer syndrome that results from mutations in several genes, including the CDKN2A gene. In addition to melanoma, certain other malignancies such as pancreatic cancer are known to occur more frequently in family members who carry the mutation. However, as these families have been followed over time, additional cancers have been observed in both carriers and noncarriers. We sought to determine whether these additional cancers occur at higher frequencies in carriers than noncarriers. We performed survival analyses using 10 FAMMM syndrome families (N = 1,085 individuals) as well as a mixed effects Cox regression, with age at last visit to the clinic or age at cancer diagnosis as our time variable. This analysis was done separately for the known FAMMM-related cancers and "other" cancer groups. The survival curves showed a significant age effect with carriers having a younger age at cancer onset than noncarriers for FAMMM-related cancers (as expected) as well as for newly associated cancers. The Cox regression reflected what was seen in the survival curves, with all models being highly significant (P = 7.15E-20 and P = 5.00E-13 for the FAMMM-related and other cancers, respectively). These analyses support the hypothesis that CDKN2A mutation carriers in FAMMM syndrome families have increased risk for early onset of several cancer types beyond the known cancers. Therefore, these individuals should be screened for additional cancers, and mutation screening should be extended to more than first-degree relatives of an index carrier patient. SIGNIFICANCE: This study shows that carriers of mutations in the CDKN2A gene in FAMMM syndrome are at increased risk for early onset of several cancer types beyond the known cancers.

Long-term risk of second malignancies in women after breast conservation therapy for ductal carcinoma in situ or early-stage breast cancer

PURPOSE

Women with ductal carcinoma in situ (DCIS) or early-stage breast cancer have an excellent prognosis, but their risk of developing second malignant neoplasms (SMNs) is not well established. We analyzed SMNs in a large cohort with long follow-up after breast conservation therapy.

METHODS

The study population comprised 755 women with DCIS (n = 135) or stage I-II breast carcinoma (n = 620). Subjects were aged 25-89 (median 55) years when they underwent breast-conserving surgery followed by radiotherapy to the entire breast (60-68Gray) between 1992 and 2001. Additional treatment included hormonal therapy and/or chemotherapy based on clinical characteristics. SMNs were grouped by site. The rate of SMNs over time was determined using the Kaplan-Meier method. To compare the probability of developing SMNs overall and for specific organs or sites, probability estimates were obtained for a 55-year-old female from the Surveillance, Epidemiology, and End Results Program (SEER).

RESULTS

Median follow-up from radiotherapy was 13.8 years. The 15-year age-adjusted probability of developing any SMN was 12.0%, close to the SEER rate of 12.1% for a non-breast malignancy. Systemic therapy and higher-dose radiotherapy (> 63 Gray) were not associated with significantly increased risks of SMNs. Compared to SEER, significantly increased risk was noted for gynecologic cancers and melanoma.

CONCLUSIONS

Most SMNs were unrelated to treatment, and the 15-year incidence was similar to that of cancer in the SEER control group-findings that should be reassuring to patients. Further risk reduction is expected from prophylactic gynecologic surgery. Continued investigations into genetic links with melanoma are warranted.

Transfection of a eukaryotic vector expressing a mutant CDK4 up-regulates POLD1 expression in SMMC-7702 cells

AIM: To construct a eukaryotic expression vector encoding a mutant CDK4 protein and to investigate the effect of transfection of this vector on POLD1 expression in SMMC-7702 cells.

METHODS: The mutant CDK4 gene was amplified by RT-PCR from total RNA isolated from the human hepatocarcinoma cell line SMMC-7721, digested, and inserted into the eukaryotic expression vector pEGFP-C1. The resultant recombinant plasmid was confirmed by sequencing. After the recombinant plasmid was transfected into SMMC-7702 cells using Lipofectamine 2000, the expression of fusion protein was observed by fluorescence microscopy, and expression of CDK4 and POLD1 mRNAs was detected by real-time PCR.

RESULTS: The eukaryotic expression plasmid GFP-CDK4 was successfully constructed. The mutant CDK4 gene contained 5 base mutation sites, 4 base insertions and 2 deletions, which caused 7 amino acids to change. Compared to non-tranfected cells or cells transfected with the pEGFP-C1 vector, cell proliferation was significantly higher in cells transfected with the recombinant vector (0.826 ± 0.08 vs 0.596 ± 0.06, 0.609 ± 0.10, F = 7.033, P < 0.05). The expression levels of CDK4 and POLD1 genes in cells transfected with the recombinant vector was significantly higher than those in the two control groups (1.94 ± 0 .11 vs 1.01 ± 0.00, 1.05 ± 0.12, F = 54.046, P < 0.01; 0.54 ± 0.04 vs 0.30 ± 0.07, 0.25 ± 0.06, F = 11.788, P < 0.05). Similar results were also obtained for the protein expression levels of CDK4 (0.65 ± 0.03 vs 0.41 ± 0.03, 0.39 ± 0.05, F = 14.665, P < 0.05) and P125 (0.54 ± 0.04 vs 0.30 ± 0.07, 0.25 ± 0.06, F = 11.788, P < 0.05).

CONCLUSION: Tranfection of the eukaryotic expression plasmid GFP-CDK4 significantly increases the proliferation and invasion of SMMC-7702 cells possibly by up-regulating POLD1 expression.

Breast cancer genomics based on biobanks

Attempts to find genes contribution to complex diseases, such as cancer, require new study designs which incorporate an efficient use of population resources and modern genotyping technologies. We describe here two approaches, used by us for the study of breast cancer, both of which take the use of biobanks. One uses a cancer registry as a source of case information, which is then linked to a biobank on blood DNA. The biobank provides also samples from matched controls. After genotyping, clinical data are retrieved from hospital records, and the results can be presented for genotype-specific cancer risks, or similarly for genotype-specific clinical and survival parameters. The second approach uses registered data on cancer in families or among twins. On defined groups of patients, paraffin tissue is collected by contacting the pathology departments of the hospitals where the patients were diagnosed. Tumor and healthy tissue is prepared and used for mutation, the loss of heterozygosity, or copy number analysis. We believe that in the era of whole-genome genotyping technologies, the importance of well-characterized sample sets cannot be overemphasized. Samples rather than technologies limit the rate of gene discovery in complex diseases.

Genetic epidemiology of cancer: From families to heritable genes

A reliable determination of familial risks for cancer is important for clinical counseling, prevention and understanding cancer etiology. Family-based gene identification efforts may be targeted if the risks are well characterized and the mode of inheritance is identified. Medically verified data on familial risks have not been available for all types of cancer but they have become available through the use of the nationwide Swedish Family-Cancer Database, which includes all Swedes born in 1932 and later with their parents, totaling over 10 million individuals. Over 150 publications have emanated from this source. The familial risks of cancer have been characterized for all main cancers and the contribution of environmental and heritable effects to the familial aggregation has been assessed. Furthermore, the mode of inheritance has been deduced by comparing risks from parental and sibling probands. Examples are shown on familial clustering of cancers, for which heritable susceptibility genes are yet unknown, such as squamous cell carcinoma of the skin, intestinal carcinoids, thyroid papillary tumors, brain astrocytomas and pituitary adenomas. Some common cancers, such as lung and kidney cancers, appear to show an early-onset recessive component because familial risks among siblings are much higher than those in families where parents are probands. Many of the cancer sites showing high familial risks lack guidelines for clinical counseling or action level. In conclusion, we recommend that any future gene identification efforts, either using linkage or association designs, devise their strategies based on data from family studies. Clinical genetic counseling would benefit from reviewing established familial risks on all main types of cancer.

Familial and attributable risks in cutaneous melanoma: effects of proband and age

We studied familial risks in invasive and in situ cutaneous melanoma by comparing the occurrence of melanoma, or discordant cancer, between parents and offspring, and between siblings, based on the Swedish Family Cancer Database of over 10 million individuals. Offspring were 0-66 y of age. Cancers were obtained from the Swedish Cancer Registry from 1961 to 1998. The study was based on 24,818 invasive and 5510 in situ cases of melanoma. Standardized incidence ratios were calculated for familial risk. The standardized incidence ratios for offspring was 2.40 (95% confidence intervals: 2.10-2.72) when only the parent had melanoma and it was 2.98 (95% confidence intervals: 2.54-3.47) when only a sibling was affected; when both a parent and a sibling were affected the standardized incidence ratios was 8.92 (95% confidence intervals: 4.25-15.31). The respective population attributable risks were 1.38, 1.20, and 0.10%. The familial risk showed a clear age dependence and somewhat higher risk in in situ melanoma than in the invasive counterpart. The highest standardized incidence ratio of 61.78 (5.82-227.19) was noted for offspring whose parent had multiple melanomas. Superficially spreading melanoma showed the highest familial risk both among invasive and in situ tumors. Melanoma associated with breast, nervous system, and skin cancers, and in situ melanoma possibly also with connective tissue and thyroid tumors and multiple myeloma.