Description
The TP53 p.Arg290His variant was identified in 4 of 1586 proband chromosomes (frequency: 0.003) from French Canadian, Spanish, Portuguese, and American individuals or families with BRCA1/2-negative breast or endometrial cancer, Li-Fraumeni syndrome (Arcand 2008, Pennington 2012, Pinto 2009, Bonache 2018) and in 26 of 127,966 (frequency: 0.0002) chromosomes from individuals in an unselected population (de Andrade 2017). The variant was identified in dbSNP (ID: rs55819519) as “With Uncertain significance, other allele”, ClinVar (classified as uncertain significance by GeneDx, Ambry Genetics, Invitae, and five other submitters; and as likely benign by University of Washington Department of Laboratory Medicine). The variant was not identified in LOVD 3.0. The variant was also identified in control databases in 42 of 277220 chromosomes at a frequency of 0.0002, increasing the likelihood this could be a low frequency benign variant (Genome Aggregation Database Feb 27, 2017). The variant was observed in the following populations: African in 2 of 24030 chromosomes (freq: 0.00008), Other in 3 of 6466 chromosomes (freq: 0.0005), Latino in 2 of 34420 chromosomes (freq: 0.00006), European in 26 of 126714 chromosomes (freq: 0.0002), East Asian in 1 of 18868 chromosomes (freq: 0.00005), Finnish in 7 of 25790 chromosomes (freq: 0.0003), and South Asian in 1 of 30780 chromosomes (freq: 0.00003), while it was not observed in the Ashkenazi Jewish population. The variant was identified in a patient with BRCA1/2-negative breast cancer who did not have a family history consistent with LFS (Arcand 2008) and a patient with LFS who presented in early childhood with multiple primary cancers, as co-occurring in trans with two TP53 variants on the other allele (p.R156H and p.R267Q); family history information was not available for the side of the family where the p.Arg290His variant segregated (Quesnel 1999). In vitro assays of cellular growth suppression and transcriptional activation demonstrated ambiguous results with the variant demonstrating complete loss of function, partial function, or function comparable to wildtype (Quesnel 1999, Zerdoumi 2017, Monti 2011). The p.Arg290 residue is not conserved in mammals and four out of five computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) do not suggest a high likelihood the His variant impacts the protein; this information is not predictive enough to rule out pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) do not predict a difference in splicing. Altogether, data from family histories, population frequencies, and functional assays are inconsistent and could represent either a benign variant identified in affected individuals as a result of increased population frequency or a pathogenic, hypomorphic variant with reduced penetrance. In summary, based on the above information, the clinical significance of this variant cannot be determined with certainty at this time. This variant is classified as a variant of uncertain significance.
| # | Sample | Method | Observation |
|---|
| Origin | Affected | Number tested | Tissue | Purpose | Method | Individuals | Allele frequency | Families | Co-occurrences |
|---|
| 1 | unknown | yes | not provided | not provided | not provided | | not provided | not provided | not provided | not provided |
