High prevalence of Pentatrichomonas hominis infection in gastrointestinal cancer patients

Abstract

Background: Pentatrichomonas hominis is a flagellated protozoan that inhabits the large intestine of humans. Although several protozoans have been proposed to have a role in cancer progression, little is known about the epidemiology of P. hominis infection in cancer patients.

Methods: To determine the prevalence of P. hominis in patients with digestive system malignancies, we collected 195 and 142 fecal samples from gastrointestinal cancer patients and residents without any complaints related to the digestive system, respectively. Each sample was detected for the presence of P. hominis by nested PCR amplifying the internal transcribed spacer (ITS) region and partial 18S rRNA gene.

Results: A significantly higher prevalence of P. hominis was found in cancer patients than that in the control population (41.54 vs 9.15%, χ² = 42.84, df = 1, P < 0.001), resulting in a 6.75-fold risk of gastrointestinal cancers (OR: 6.75, 95% CI: 3.55-12.83, P < 0.001). The highest prevalence of P. hominis infection was detected in small intestine cancer patients (60%, OR: 14.88, 95% CI: 0.82-4.58, P = 0.009) followed by liver (57.14%, χ² = 10.82, df = 1, P = 0.001) and stomach cancer patients (45.1%, χ² = 31.95, df = 1, P < 0.001). In addition, phylogenetic analysis provided some evidence supporting that human P. hominis infection might derive from animal sources.

Conclusions: To our knowledge, this study is the first report presenting the high association between P. hominis and gastrointestinal cancers. Nevertheless, whether there is any possible pathological role of P. hominis infection in cancer patients needs to be further elucidated.

Keywords: Colorectal cancer; Epidemiology; Gastrointestinal cancer; Pentatrichomonas hominis; Stomach cancer.

Fig. 1

Pie graph of the proportion of P. hominis infections in gastrointestinal cancers (left and middle) and control population (right)

Fig. 2

Alignment of the sequences of partial 18S rRNA gene of P. hominis isolated from humans in the present study with reference sequences. Nucleotides that differ from those in the reference sequences are indicated. Dots represent the consensus nucleotides in all the sequences. Abbreviation: CCH, China Changchun human

Fig. 3

Phylogenetic relationships between P. hominis obtained in the present study (marked with blue circle or blue triangle) and other known trichomonads were inferred using the maximum likelihood analysis of the partial 18S rRNA gene and ITS sequence based on the genetic distance calculated by Kimura 2-parameter model. The numbers at the branches represent the percentage of replicate trees in the bootstrap test (1000 replicates). a 18S rRNA sequences. b ITS sequences. Abbreviation: CCH, China Changchun human