Microsatellite abnormalities in plasma of patients with breast carcinoma: concordance with the primary tumour.

Abstract

Aims-To detect microsatellite abnormalities in the primary tumours and plasma of patients with breast carcinoma. Methods-Plasma was obtained from 17 breast carcinoma patients before surgery. Corresponding tumour and benign lymph node (control) samples for each of the carcinoma patients were obtained from paraYn blocks. DNA was extracted from the plasma samples and the paraYn embedded tissue using previously described methods. Results-The 17 primary tumours showed two examples of loss of heterozygosity and three examples of microsatellite instability; the 17 plasma samples showed three and one, respectively. Many of the longer microsatellites (over 200 base pairs) were diYcult to amplify from plasma. The investigations suggested that this was because of the highly fragmented nature of plasma DNA. Only one example of loss of heterozygosity and one example of microsatellite instability showed a concordant pattern in both primary tumour and plasma. These were both in the same patient. Conclusions-DNA mutations concordant with those in the primary carcinomas can occasionally be detected in the plasma of patients with breast carcinoma. However, the frequency would have to be markedly improved before this could be of any diagnostic value.

RNA is more sensitive than DNA in identification of breast cancer patients bearing tumor nucleic acids in plasma

“…We suggested in Genes Chromosomes and Cancer that the finding of several neoplastic clones could explain some non-matched alterations between plasma and tumor DNA ). Tumor-specific DNA has been detected in the peripheral blood of patients with some of the most prevalent carcinomas, such as lung (Chen et al, 1996;Esteller et al, 1999;González et al, 2000), breast (Chen et al, 1999;Mayall et al, 1999;Silva et al, 1999), and colon cancer (Anker et al, 1997;Kopreski et al, 1997;Hibi et al, 1998). In addition to DNA, tumor RNA circulates in the plasma and serum of cancer patients (Kopreski et al, 1999;Lo et al, 1999;Chen et al, 2000;Silva et al, 2001).…”

Heterogeneous tumor clones as an explanation of discordance between plasma DNA and tumor DNA alterations

“…Some authors suggest that these nonmatched alterations are pitfalls, arguing that the DNA is not pure enough and that small quantities of template can result in polymerase chain reaction artifacts (Chen et al, 1999;Mayall et al, 1999;Coulet et al, 2000). On the other hand, other investigators propose the existence of heterogeneous tumor clones as an alternative explanation (Chen et al, 1996;Goessl et al, 1998), although this possibility has not been proved.…”

Loss of heterozygosity in serial plasma DNA samples during follow‐up of women with breast cancer

“…Third, breast cancers lack a signature genetic abnormality, but nearly all tumors are characterized by microsatellite alterations, specifically allele imbalance (AI) or loss of heterozygosity (LOH) at multiple loci 7, 8. Nearly every breast tumor has an individual pattern of AI/LOH,7 which constitutes its “fingerprint.” Taken together, it is not surprising that several reports identify microsatellite alterations in the peripheral blood of patients with breast cancer 9, 10, 11, 12, 13, 14…”

“…In those reports, LOH is seen in plasma or serum DNA of breast cancer subjects, with prevalence ranging between 18–66% of cases 9, 10, 11, 12, 13, 14. Novel microsatellite alleles, representing micro‐satellite instability (MI) are occasionally seen.…”

“…In contrast, LOH or MI are rarely, if ever, detected in normal controls' plasma DNA 11, 13, 15, 16, 17. Blood samples are usually collected at a single time point, either pre‐10, 12, 13, 14 or postoperatively,11 from subjects who usually have early stage disease, although some with advanced disease have been included. The proportion of LOH (pLOH) detected in primary tumors varies (12–90% of informative sites), as does the concordance of LOH (i.e., matched LOH) between tumor and blood DNA (estimated between 33–100%9, 10, 11, 14).…”