Human papillomavirus DNA in plasma of patients with cervical cancer

Abstract

Background: Human papillomavirus (HPV) is a crucial etiological factor for cervical cancer (CC) development. From a diagnostic view-point, the consistent presence of HPV in CC allows the viral DNA to be used as a genetic marker. The aims of this study were to evaluate the presence, physical status and clinical significant of HPV DNA in circulation of CC patients.

Results: Whereas 6 out of 50 (12%) HPV positive CC patients revealed plasma HPV DNA, it was detected in none of 20 normal controls or 13 HPV negative CC cases. The plasma DNA exhibited an HPV type identical to the HPV in the primary tumors and the DNA from both sources was integrated into host genome. Interestingly, several findings suggested an association between plasma HPV DNA and metastasis. First, three of the HPV DNA positive cases were CC patients with clinical stage IVB or recurrence with distance metastases (P = 0.001, RR = 15.67). Second, the amount of plasma HPV DNA from metastatic patients to be three times more than three other patients without metastases. Finally, the later cases had tendency to develop recurrence distant metastases within one year after complete treatment when compared with other HPV associated CC patients with the same stage but without the present of plasma HPV DNA.

Conclusions: The plasma HPV DNA originated from the CC, was associated with metastasis and could be used as a marker representing the circulating free CC DNA.

Figure 1

HPV DNA in plasma of patients with cervical cancer. (A) PCR generating 243-bp DNA fragments of HPV E6 gene (B) Dot-blot hybridization for HPV 18 probe Lanes a1-f1 were positive controls using purified plasmids of HPV type 6, 11, 16, 18, 31 and 33, respectively Lanes a2-f2 were plasma DNA from patients number 4, 106, 148, 161, 183, and 59 respectively Lanes a3-f3 were tumor DNA from the same patients as lanes a2-f2 (C) PCR generating 1392- and 1028-bp DNA fragments of human PIGR genomic sequence and HPV-18 E2 (D) PCR generating 1026, 1028-bp DNA fragments of HPV 16 and 18 E2 gene, respectively, from tumor DNA on a 2% agarose gel stained with ethidium bromide (E) Duplex PCR generating 243- and 177-bp DNA fragments of HPV E6 gene and human ZP3 genomic sequence, respectively From left to right of A, C-E: M, 100-bp ladder standard DNA size marker; - and +, PCR products of the negative control (double-distilled water) and positive control (Hela cell line for A and E; purified plasmids for D; and for C, DNA from human leukocyte for PIGR and purified HPV 18 DNA plasmid for E2 gene), respectively; numbers without p indicate PCR products of tumor DNA; numbers with p indicate PCR products of plasma DNA of CC patients Number 1061p and 1062p were plasma DNA from patient 106 but the samples were collected at different time