Evaluation of DNA from the Papanicolaou Test to Detect Ovarian and Endometrial Cancers

Abstract

Papanicolaou (Pap) smears have revolutionized the management of patients with cervical cancers by permitting the detection of early, surgically curable tumors and their precursors. In recent years, the traditional Pap smear has been replaced by a liquid-based method, which allows not only cytologic evaluation but also collection of DNA for detection of human papillomavirus, the causative agent of cervical cancer. We reasoned that this routinely collected DNA could be exploited to detect somatic mutations present in rare tumor cells that accumulate in the cervix once shed from endometrial or ovarian cancers. A panel of genes that are commonly mutated in endometrial and ovarian cancers was assembled with new whole-exome sequencing data from 22 endometrial cancers and previously published data on other tumor types. We used this panel to search for mutations in 24 endometrial and 22 ovarian cancers and identified mutations in all 46 samples. With a sensitive massively parallel sequencing method, we were able to identify the same mutations in the DNA from liquid Pap smear specimens in 100% of endometrial cancers (24 of 24) and in 41% of ovarian cancers (9 of 22). Prompted by these findings, we developed a sequence-based method to query mutations in 12 genes in a single liquid Pap smear specimen without previous knowledge of the tumor’s genotype. When applied to 14 samples selected from the positive cases described above, the expected tumor-specific mutations were identified. These results demonstrate that DNA from most endometrial and a fraction of ovarian cancers can be detected in a standard liquid-based Pap smear specimen obtained during routine pelvic examination. Although improvements need to be made before applying this test in a routine clinical manner, it represents a promising step toward a broadly applicable screening methodology for the early detection of gynecologic malignancies.

Ultra-deep sequencing detects ovarian cancer cells in peritoneal fluid and reveals somatic TP53 mutations in noncancerous tissues

“…HGSOC disseminates early and preferentially to the peritoneal cavity, suggesting that cancer cells may be more abundant in peritoneal fluid than in the relatively distant uterine cavity or cervix, as previously attempted by other studies (5,14).…”

“…"Molecular tagging" of single-stranded DNA decreases the rate of false mutations to less than 1 per 10,000 sequenced nucleotides and has been successfully applied to the detection of mutant cancer DNA in a variety of clinical samples (2)(3)(4)(5)(6). However, this false positive error rate limits the specificity of this method in challenging situations in which ultra-deep sequencing is needed to detect extremely low frequency mutant molecules (e.g., <1/10,000), as is the case of ovarian cancer DNA in Pap smears (5). Because true mutations are indistinguishable from artifacts, compromised specificity leads to lower sensitivity and overall low diagnostic accuracy.…”

Targeting Wnts at the Source—New Mechanisms, New Biomarkers, New Drugs

“…Hence, RNF43 and ZNRF3 mutations, by sensitizing cells to Wnts, may also be predictive of response to both PORCN inhibitors and Frizzled antibodies. Mutations in RNF43 are surprisingly common, occurring in 18% to 27% of endometrial cancers, 3% to 5% of pancreatic cancers, 21% ovarian mucinous carcinomas, and 38.5% liver fluke associated cholangiocarcinomas (45)(46)(47)(48). Notably, up to 18% of colorectal cancers have RNF43 mutations, often associated with mismatch repair deficient, microsatellite instability (MSI þ ) cancers (46).…”

The primate vaginal microbiome: Comparative context and implications for human health and disease

“…These cancers are notably difficult to detect, rarely caught early, and have a very poor prognosis (Stirling et al, 2005). However, recent findings indicate that ovarian and endometrial cancerous cells can be found in the vagina (Kinde et al, 2013). While pap smears (i.e., brushing the cervix to remove cells) are the standard clinical practice used to detect cervical cancer, findings from microbial studies of the vagina (e.g., Kim et al, 2009) indicate that localized sampling may be inefficient for detecting microbial populations (and presumably rare cancerous cells) dispersed through the vagina.…”