Abstract P1-12-10: Regimen-specific rates of chemotherapy-related amenorrhea in breast cancer survivors

Background: Chemotherapy can damage the ovaries and cause amenorrhea, a surrogate for infertility. Young women often wish to understand and minimize their risk of chemotherapy-related amenorrhea (CRA). However, the incidence of CRA with regimens that do not include either an anthracycline or cyclophosphamide is poorly studied. For patients with HER-2 positive disease, these anthracycline and cyclophosphamide-sparing regimens (e.g., docetaxel-carboplatin) are common (in combination with Her-2 directed therapy) in both the neoadjuvant and adjuvant settings.

Methods: Women diagnosed with breast cancer under age 50 and within the past 10 years were recruited through a Dr. Susan Love Research Foundation Army of Women e-mail blast. Those who provided their contact information were mailed a consent form and medical record authorization form. Participants then received a web-based survey that inquired about receipt of and type of chemotherapy (including date of last dose) and date of last menstrual period (LMP). Patient-reported LMP was compared to date of final chemotherapy dose to determine if the LMP occurred before (defined as “CRA”) or after the last chemotherapy dose. When available, medical record data was used in place of survey data regarding type of chemotherapy used. Exclusion criteria included: LMP prior to diagnosis date, receipt of multiple chemotherapy regimens or no chemotherapy regimens, receipt of ovarian suppression medications (which interfere with interpretation of menstrual data), surgical menopause prior to or at the same time as diagnosis, a cancer diagnosis more than 10 years prior, incomplete menstrual data on the survey, report of an unknown chemotherapy regimen, and no date available for the last chemotherapy dose without an LMP within a month prior to survey completion. Fisher Exact test was used to compare CRA rates between regimens. Rates after two anthracycline-sparing regimens (taxane/cyclophosphamide; taxane/carboplatin) were compared to rates after anthracycline/cyclophosphamide/taxane.

Results: 273 women consented to participate in this study, 258 of whom filled out the web survey. 151 of them were eligible for this analysis with a median age at diagnosis of 41 (range 24-49) and a median time from last chemotherapy dose to survey of 62.5 months (range 2-138). CRA occurred in 51.2% of the 86 participants who received an anthracycline, cyclophosphamide, and a taxane, in 41.9% of the 43 participants who received only a taxane and cyclophosphamide (p=0.35), and in 13.3% of the 15 participants who received carboplatin with a taxane (p=0.01). When the 11 patients who were <12 months since last chemotherapy were excluded, CRA rates changed minimally. Age did not differ by regimen, but median time since chemotherapy was shorter in the taxane/carboplatin group (35 months vs. 68 months). Trastuzumab with or without pertuzumab was administered in 100% of patients who received carboplatin/taxane, in 23.3% of patients who received taxane and cyclophosphamide, and in 22.1% of patients who received anthracycline/cyclophosphamide/taxane.

Conclusions: This study suggests that carboplatin/taxane may be substantially less gonadotoxic than cyclophosphamide-based (neo)adjuvant regimens. Further research is necessary to confirm these findings.

Citation Format: Gast KC, Cathcart-Rake EJ, Norman A, Eshragi L, Obidegwu N, Yost K, Nichols HB, Rosenberg S, Su HI, Stewart E, Couch F, Vachon C, Ruddy KJ. Regimen-specific rates of chemotherapy-related amenorrhea in breast cancer survivors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-12-10.

Abstract P1-06-07: Mayo clinic TNBC outcome calculator: A clinical calculator to predict disease relapse and survival in women with triple-negative breast cancer

Purpose: Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype with substantial risks of disease recurrence. While cytotoxic chemotherapy is commonly administered and reduces recurrence, disease outcomes vary considerably and few prognostic tools are available for risk stratification for TNBC patients. We constructed and validated clinical calculators for invasive-disease free survival (IDFS) and overall survival (OS) for TNBC and compared their performance against AJCC-based models which include only tumor size and nodal status.

Methods: From a surgical cohort of 9,982 patients who underwent breast cancer surgery at Mayo Clinic between January 1985 and December 2012, 605 centrally reviewed TNBC patients were identified and used to construct Cox models for IDFS and OS. Patients treated with neoadjuvant chemotherapy were excluded. Variables considered included age, menopausal status, tumor size, nodal status, Nottingham grade, type of breast surgery (mastectomy vs. lumpectomy), adjuvant radiation therapy, adjuvant chemotherapy, Ki67, stromal tumor infiltrating lymphocytes (sTILs), and neutrophil-to-lymphocyte ratio (NLR). Missing values were imputed using single imputation with all variables (including outcomes) included in the imputation model. Backward step-down procedure was used for model selections. The final models were internally validated for calibration and discrimination using bootstrapping methods and compared with AJCC-based models.

Results: For both IDFS and OS, higher sTIL's, less extensive nodal involvement, use of adjuvant chemotherapy, and lower NLR were significant predictors of improved clinical outcomes. Premenopausal status and younger age were additionally predictive of improved IDFS and OS, respectively. Models for IDFS and OS have good calibration and are associated with bias-corrected C-indices of 0.68 and 0.71, respectively, as compared with C-indices of 0.59 and 0.62 for AJCC-based models.

Conclusions: Our data indicate that a clinical calculator that includes sTIL's, NLR, menopausal status, age, nodal involvement as well as chemotherapy use can provide significantly greater prediction of clinical risk than tumor size and nodal status alone. These tools may be used to identify TNBC patients at elevated risk of disease relapse and to aid physician's communication with patients regarding their long-term disease outlook and planning treatment strategies. External validation is required to further evaluate broader applicability of this tool, which was developed utilizing a single-institutional experience.

Citation Format: Polley M-YC, Leon-Ferre RA, Liu H, Gilbert J, Cafourek V, Hillman DW, Negron V, Boughey JC, Liu MC, Ingle JN, Kalari K, Couch F, Visscher DW, Goetz MP. Mayo clinic TNBC outcome calculator: A clinical calculator to predict disease relapse and survival in women with triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-06-07.

Gene-panel testing of breast and ovarian cancer patients identifies a recurrent RAD51C duplication

Gene-panel sequencing allows comprehensive analysis of multiple genes simultaneously and is now routinely used in clinical mutation testing of high-risk breast and ovarian cancer patients. However, only BRCA1 and BRCA2 are often analyzed also for large genomic changes. Here, we have analyzed 10 clinically relevant susceptibility genes in 95 breast or ovarian cancer patients with gene-panel sequencing including also copy number variants (CNV) analysis for genomic changes. We identified 12 different pathogenic BRCA1, BRCA2, TP53, PTEN, CHEK2, or RAD51C mutations in 18 of 95 patients (19%). BRCA1/2 mutations were observed in 8 patients (8.4%) and CHEK2 protein-truncating mutations in 7 patients (7.4%). In addition, we identified a novel duplication encompassing most of the RAD51C gene. We further genotyped the duplication in breast or ovarian cancer families (n = 1149), in unselected breast (n = 1729) and ovarian cancer cohorts (n = 553), and in population controls (n = 1273). Seven additional duplication carries were observed among cases but none among controls. The duplication associated with ovarian cancer risk (3/590 of all ovarian cancer patients, 0.5%, P = .032 compared with controls) and was found to represent a large fraction of all identified RAD51C mutations in the Finnish population. Our data emphasizes the importance of comprehensive mutation analysis including CNV detection in all the relevant genes.

Evaluation of ACMG-Guideline-Based Variant Classification of Cancer Susceptibility and Non-Cancer-Associated Genes in Families Affected by Breast Cancer

Sequencing tests assaying panels of genes or whole exomes are widely available for cancer risk evaluation. However, methods for classification of variants resulting from this testing are not well studied. We evaluated the ability of a variant-classification methodology based on American College of Medical Genetics and Genomics (ACMG) guidelines to define the rate of mutations and variants of uncertain significance (VUS) in 180 medically relevant genes, including all ACMG-designated reportable cancer and non-cancer-associated genes, in individuals who met guidelines for hereditary cancer risk evaluation. We performed whole-exome sequencing in 404 individuals in 253 families and classified 1,640 variants. Potentially clinically actionable (likely pathogenic [LP] or pathogenic [P]) versus nonactionable (VUS, likely benign, or benign) calls were 95% concordant with locus-specific databases and Clinvar. LP or P mutations were identified in 12 of 25 breast cancer susceptibility genes in 26 families without identified BRCA1/2 mutations (11%). Evaluation of 84 additional genes associated with autosomal-dominant cancer susceptibility identified LP or P mutations in only two additional families (0.8%). However, individuals from 10 of 253 families (3.9%) had incidental LP or P mutations in 32 non-cancer-associated genes, and 9% of individuals were monoallelic carriers of a rare LP or P mutation in 39 genes associated with autosomal-recessive cancer susceptibility. Furthermore, 95% of individuals had at least one VUS. In summary, these data support the clinical utility of ACMG variant-classification guidelines. Additionally, evaluation of extended panels of cancer-associated genes in breast/ovarian cancer families leads to only an incremental clinical benefit but substantially increases the complexity of the results.

Abstract P4-10-07: Genetic predictors of chemotherapy-related amenorrhea

Background: Chemotherapy-related amenorrhea (CRA) impacts quality of life and reproductive options, and may play a role in treatment decision-making for young breast cancer patients. Although age, increasing doses of alkylating agents, and tamoxifen are known to increase the risk of chemotherapy-related amenorrhea (CRA), it is difficult to predict which women will develop CRA in order to inform fertility preservation and treatment decisions. We sought to investigate whether single nucleotide polymorphisms (SNPs) that have been associated with a younger age at natural menopause and ovarian reserve in non-oncologic populations were predictive of CRA in two large German clinical trials that administered gonadotoxic chemotherapy.

Methods: A total of 1322 premenopausal participants under age 50 who enrolled in SUCCESS B (a phase 3 trial of FEC-docetaxel-trastuzumab +/- gemcitabine for high risk early stage breast cancer) or SUCCESS C (a phase 3 trial of FEC-docetaxel-cyclophosphamide vs. docetaxel-cyclophosphamide that also tested the efficacy of a weight loss intervention in early stage breast cancer patients) were eligible for this study. We excluded patients who were receiving ovarian suppression. On these trials, menstrual status was self-reported as amenorrheic or not every three months after chemotherapy. Bloods were stored and patients provided consent for DNA analysis. We genotyped nine candidate SNPs in six genes (rs2002555 and rs11170547 in AMHR2, rs6166 in FSHR, rs10852344 <60kb from TNFRSF17/RUNDC2A/ GSPT1, rs12461110 in NLRP11, rs1801133 in MTHFR, rs2066470 in MTHRF, rs3810682 in BMP15, and rs615942 in COASY), and examined their association with CRA at 12-month and 24-month time points using logistic regression adjusted for age, BMI, and tamoxifen.

Results: Of the 554 eligible women with SNP data and menstrual data at 12 months, 70% reported CRA; of the 458 eligible women with SNP data and menstrual data at 24 months, 69% reported CRA. The two SNPs in AMHR2 showed suggestive associations with CRA at 12 and 24 months. [Final results pending].

Conclusions: Genetic variation in AMHR2 may be associated with CRA. Additional research will be needed to validate these findings in other breast cancer survivors and to identify additional SNPs that may be associated with CRA. Together with other clinical factors, genetic variation may improve our ability to predict who will experience CRA, and may inform reproductive and treatment decision-making in cancer patients.

Citation Format: Ruddy KJ, Rack B, Schwitulla J, Lambrechts D, Haeberle L, Schramm A, Trapp E, Scholz C, Beutler AS, Ginsburg E, Couch F, Partridge AH, Wang L, Weinshilboum RM, Janni W, Vachon C, Fasching P. Genetic predictors of chemotherapy-related amenorrhea. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-10-07.

Functional variants at the 11q13 risk locus for breast cancer regulate cyclin D1 expression through long-range enhancers

Analysis of 4,405 variants in 89,050 European subjects from 41 case-control studies identified three independent association signals for estrogen-receptor-positive tumors at 11q13. The strongest signal maps to a transcriptional enhancer element in which the G allele of the best candidate causative variant rs554219 increases risk of breast cancer, reduces both binding of ELK4 transcription factor and luciferase activity in reporter assays, and may be associated with low cyclin D1 protein levels in tumors. Another candidate variant, rs78540526, lies in the same enhancer element. Risk association signal 2, rs75915166, creates a GATA3 binding site within a silencer element. Chromatin conformation studies demonstrate that these enhancer and silencer elements interact with each other and with their likely target gene, CCND1.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Abstract P6-04-02: Profiling of BRCA1 Mutated Breast Tumours Using a Breast Cancer Specific Microarray To Identify a Profile of BRCAl-Deficiency

Background

The BRCA 1 tumour suppressor gene is mutated in a significant proportion of hereditary breast cancer cases. Additionally, downregulation of BRCA1 mRNA and protein expression is reported in approximately one third of sporadic breast cancers. BRCA1 is strongly implicated in the maintenance of genomic stability by its involvement in multiple cellular pathways including: DNA damage signalling, DNA repair, cell cycle regulation, protein ubiquitination, chromatin remodelling, transcriptional regulation and apoptosis. To date, gene expression profiling has identified: (1) at least five breast cancer subtypes and (2) that BRCA1 mutant tumours segregate with basal-like breast cancers. These studies also provide evidence that breast cancers with germline mutations in BRCA1 are different from non BRCA1-related tumours. The main aim of this study is to investigate the underlying biology of BRCA1-mutated breast cancer. Methods

Extensive gene expression profiling and data analysis were performed on a cohort of 70 FFPE (Formalin Fixed Paraffin Embedded) derived BRCA 1 mutated breast tumours and matched sporadic controls using the Almac Breast Cancer DSATM research tool. Functional analysis was performed with DAVID and METACORE. Validation of gene targets was performed by qRT-PCR and Western blotting. Results

A list of differentially expressed transcripts has been derived from the comparison of these BRCA1 mutant breast tumours and matched sporadic controls. Functional analysis of this gene list has identified the key genes and molecular pathways that are deregulated in these tumours. BRCA1 deficiency was associated with deregulation of pathways involved in: (1) immune response, (2) metastasis and invasion, (3) cytoskeletal remodelling, (4) spindle assembly and chromosome separation, (5) apoptosis and survival. Validation of the key genes underlying this BRCA1-deficient breast cancer profile has been performed. Conclusions

This approach has revealed a set of transcripts that could potentially be used to identify both hereditary and sporadic breast cancer patients with BRCA1- deficiency. The ability to perform gene expression profiling from FFPE derived breast tissue could also have significant clinical application.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-02.

Rapid progression of prostate cancer in men with a BRCA2 mutation

Men with BRCA2 mutations have been found to be at increased risk of developing prostate cancer. There is a recent report that BRCA2 carriers with prostate cancer have poorer survival than noncarrier prostate cancer patients. In this study, we compared survival of men with a BRCA2 mutation and prostate cancer with that of men with a BRCA1 mutation and prostate cancer. We obtained the age at diagnosis, age at death or current age from 182 men with prostate cancer from families with a BRCA2 mutation and from 119 men with prostate cancer from families with a BRCA1 mutation. The median survival from diagnosis was 4.0 years for men with a BRCA2 mutation vs 8.0 years for men with a BRCA1 mutation, and the difference was highly significant (P<0.01). It may be important to develop targeted chemotherapies to treat prostate cancer in men with a BRCA2 mutation.

Constant denaturant gel electrophoresis (CDGE) in BRCA1 mutation screening

Screening for mutations in the breast and ovarian cancer susceptibility gene, BRCA1, is complicated by the wide spectrum of mutations found in this large gene. In the present study a constant denaturant gel electrophoresis (CDGE) mutation screening strategy was established for approximately 80% of the genomic coding sequence (exons 2, 11, 13-16, 20, 24). This strategy was applied to screen genomic DNA from 50 familial breast and/or ovarian cancer patients who had previously been examined for BRCA1 mutations by SSCP. A total of 14 carriers of 12 distinct disease-associated mutations and 7 carriers of 6 distinct rare substitutions leading to amino acid substitutions were identified. The SSCP failed to detect 40% of the different deletions/insertions (4/10) and 75% (6/8) of the different base substitutions leading to terminating codons or rare amino acid changes. SSCP did, however, identify one rare base substitution that could not be detected in the CDGE screening. To evaluate the CDGE mutation screening strategy further, 25 unrelated patients from Norwegian breast and/or ovarian cancer families were examined for BRCA1 mutations using a combined genomic DNA/cDNA approach covering the entire coding sequence of the gene. A total of six mutation carriers were detected, all of whom had cases of ovarian cancer in their families. Three patients from independent families carried an 1135insA mutation in exon 11, two others had a Gly484ter and an 1675delA mutation, respectively, and the sixth carried a splice mutation (5194-2 a-->c) causing deletion of exon 18. CDGE may become an efficient tool in diagnostic and population based screening for BRCA1 mutations.

Clinical options for women at high risk for breast cancer

Women at hereditary risk of breast cancer face a difficult clinical decision. Each of the options available to them has unique advantages and disadvantages that are summarized in Table 9. Many components enter a high-risk woman's decision: her objective risk of breast cancer; clinical features, such as the consistency of breast tissue and resultant ease of examination; breast density on mammography; personal characteristics, including her experience with cancer within her family; her role and [table: see text] responsibilities within her own nuclear family; her values and goals; her experiences with the medical system; and her subjective assessment of risk. It is generally believed that women significantly overestimate their risk of breast cancer. Thus, it is vital that a woman at risk have access to a genetic counselor who can provide accurate assessment of her risk. Women should be encouraged to take time to understand their risk level and the advantages and disadvantages of the options before them.

The complete BRCA2 gene and mutations in chromosome 13q-linked kindreds

Breast carcinoma is the most common malignancy among women in developed countries. Because family history remains the strongest single predictor of breast cancer risk, attention has focused on the role of highly penetrant, dominantly inherited genes in cancer-prone kindreds (1). BRCA1 was localized to chromosome 17 through analysis of a set of high-risk kindreds (2), and then identified four years later by a positional cloning strategy (3). BRCA2 was mapped to chromosomal 13q at about the same time (4). Just fifteen months later, Wooster et al. (5) reported a partial BRCA2 sequence and six mutations predicted to cause truncation of the BRCA2 protein. While these findings provide strong evidence that the identified gene corresponds to BRCA2, only two thirds of the coding sequence and 8 out of 27 exons were isolated and screened; consequently, several questions remained unanswered regarding the nature of BRCA2 and the frequency of mutations in 13q-linked families. We have now determined the complete coding sequence and exonic structure of BRCA2 (GenBank accession #U43746), and examined its pattern of expression. Here, we provide sequences for a set of PCR primers sufficient to screen the entire coding sequence of BRCA2 using genomic DNA. We also report a mutational analysis of BRCA2 in families selected on the basis of linkage analysis and/or the presence of one or more cases of male breast cancer. Together with the specific mutations described previously, our data provide preliminary insight into the BRCA2 mutation profile.

Haplotype and phenotype analysis of six recurrent BRCA1 mutations in 61 families: results of an international study

Several BRCA1 mutations have now been found to occur in geographically diverse breast and ovarian cancer families. To investigate mutation origin and mutation-specific phenotypes due to BRCA1, we constructed a haplotype of nine polymorphic markers within or immediately flanking the BRCA1 locus in a set of 61 breast/ovarian cancer families selected for having one of six recurrent BRCA1 mutations. Tests of both mutations and family-specific differences in age at diagnosis were not significant. A comparison of the six mutations in the relative proportions of cases of breast and ovarian cancer was suggestive of an effect (P = .069), with 57% of women presumed affected because of the 1294 del 40 BRCA1 mutation having ovarian cancer, compared with 14% of affected women with the splice-site mutation in intron 5 of BRCA1. For the BRCA1 mutations studied here, the individual mutations are estimated to have arisen 9-170 generations ago. In general, a high degree of haplotype conservation across the region was observed, with haplotype differences most often due to mutations in the short-tandem-repeat markers, although some likely instances of recombination also were observed. For several of the instances, there was evidence for multiple, independent, BRCA1 mutational events.

A collaborative survey of 80 mutations in the BRCA1 breast and ovarian cancer susceptibility gene. Implications for presymptomatic testing and screening

OBJECTIVES

To report the initial experience of an international group of investigators in identifying mutations in the BRCA1 breast and ovarian cancer susceptibility gene, to assess the spectrum of such mutations in samples from patients with different family histories of cancer, and to determine the frequency of recurrent mutations.

DESIGN

Nine laboratories in North America and the United Kingdom tested for BRCA1 mutations in DNA samples obtained from a total of 372 unrelated patients with breast or ovarian cancer largely chosen from high-risk families. Three of these laboratories also analyzed a total of 714 additional samples from breast or ovarian cancer cases, including 557 unselected for family history, for two specific mutations that had been found to recur in familial samples.

PARTICIPANTS

A total of 1086 women with either breast or ovarian cancer.

MAIN OUTCOME MEASURE

The detection of sequence variation in patients' DNA samples that is not found in sets of control samples.

RESULTS

BRCA1 mutations have now been identified in a total of 80 patient samples. Thirty-eight distinct mutations were found among 63 mutations identified through a complete screen of the BRCA1 gene. Three specific mutations appeared relatively common, occurring eight, seven, and five times, respectively. When specific tests for the two most common mutations were performed in larger sets of samples, they were found in 17 additional patients. Mutations predicted to result in a truncated protein accounted for 86% of the mutations detected by complete screening.

CONCLUSIONS

The high frequency of protein-terminating mutations and the observation of many recurrent mutations found in a diverse set of samples could lead to a relatively simple diagnostic test for BRCA1 mutations. More data must be accumulated to address specifically the sensitivity and specificity of such a diagnostic testing procedure and to better estimate the age-specific risk for breast and ovarian cancer associated with such mutations.

Assignment of the human gene for the alpha 1 subunit of the skeletal muscle DHP-sensitive Ca2+ channel (CACNL1A3) to chromosome 1q31-q32

A human clone corresponding to the gene encoding the alpha 1 subunit of the skeletal muscle dihydropyridine-sensitive calcium channel (CACNL1A3) has been isolated and partially sequenced. Oligonucleotides based on this sequence were used in a polymerase chain reaction to amplify specifically the human gene in human-rodent somatic cell hybrids, allowing the assignment of CACNL1A3 to chromosome 1. A polymorphic dinucleotide repeat also was identified in the human clone and using PCR was typed on a subset of the CEPH families. Multipoint linkage analysis places the CACNL1A3 gene between D1S52 and D1S70, on chromosome 1q31-q32.

A cysteine-for-arginine substitution (R614C) in the human skeletal muscle calcium release channel cosegregates with malignant hyperthermia

A point mutation in the human gene for the skeletal muscle calcium release channel (ryanodine receptor [RYR1]) correlates with inheritance of malignant hyperthermia in a family of Northern European descent. The substitution of thymine for cytosine at position 1840 of the RYR1 transcript results in a cysteine-for-arginine substitution at position 614 (R614C) of the amino acid sequence. The mutation was absent in 59 normal individuals from the general population, in 61 additional unrelated malignant hyperthermia-susceptible patients, and in 18 patients with malignant hyperthermia associated with other inherited or congenital diseases. Together with reports of an equivalent mutation in six susceptible pig strains and an identical mutation in one other human pedigree, these findings suggest that the cysteine-for-arginine mutation represents a shared calcium release channel pathogenesis between porcine malignant hyperthermia and a subset of mutations responsible for the human malignant hyperthermia syndrome.