Microbial Dysbiosis Is Associated With Human Ovarian Cancer

Objective:In recent years, a greater appreciation for the microorganisms inhabiting the human body and causing disease, especially the relationship with neoplasms, has emerged and is becoming increasingly emphasized by researchers and clinicians. Ovarian carcinoma has been considered a multifactorial and heterogeneous disease, the origin and etiology of which are still poorly understood. However, few studies have been conducted to investigate the population diversity of microbiota in ovarian cancer tissues. Our work was conducted to analyze the diversity and composition of the microbiota of ovarian cancer and normal distal fallopian tube tissues using 16S rRNA high-throughput sequencing methods.Methods:71 fresh ovarian cancer tissues diagnosed of high grade serous pathological pattern were collected and 67 fresh normal distal fallopian tube tissues derived from patients of adenomyoma or myoma of uterus undergoing uterine plus bilateral salpingo-oophorectomy were also collected. The total DNA from twenty five ovarian cancer tissues (C group) paired with twenty five normal distal fallopian tube tissues (N group) were extracted and applied to 16S rRNA sequencing using fusion primers targeting the bacterial 16S V3-V4 rRNA with indexing barcodes on the Illumina Miseq with 150bp paired-end reads. In addition, we designed the specific primers to detect the associated bacterial with real-time quantitative PCR (RT-qPCR) between forty-six fresh ovarian cancer tissues and forty-one fresh normal distal fallopian tube tissues in an independent samples cohort. Finally, Human Antibacterial Response PCR Arrays were introduced to explore the potential mechanisms of microorganisms as possible tumor promoters or initiators.Results:(1) The results of 16S rRNA sequencing demonstrated that a composition change in the microbiota of ovarian cancer tissues and normal distal fallopian tube tissues. (2) The diversity and richness indices were decreased in ovarian cancer tissues compared to normal distal fallopian tube tissues (the Shannon index:P= 0.025), although, the number of OTUs and Simpson index had not a statistical significant (P= 0.1774, P= 0.0727, respectively). (3) RT-qPCR suggested that the Proteobacteria abundances were significantly increased in ovarian cancer tissues that that in normal tissues detected in an independent validation phase (P= 0.0050), whereas the Firmicutes abundances were significantly decreased in ovarian cancer tissues than in normal tissues in an independent validation phase (P= 0.0002) at the phylum level. At the genus level, the Acinetobacter abundances were statistically increased in ovarian cancer tissues that that in normal tissues detected in an independent validation phase (P= 0.0003), whereas the Lactococcus abundances were statistically decreased in ovarian cancer tissues compared in normal tissues in an independent validation phase (P= 0.0100). Moreover, at the species level, the Acinetobacter_lwoffii abundances were significantly increased in ovarian cancer tissues that that in normal tissues detected in an independent validation phase (P< 0.0001), whereas the Lactococcus_piscium abundances were significantly decreased in ovarian cancer tissues than in normal tissues in an independent validation phase (P< 0.0001), which were partly in accordance with the results of 16S sequencing. (4) Based on Human Antibacterial Response PCR Array, the data suggested that most majority of antibacterial response genes (especial the microbial sensors related genes, downstream signaling molecules and antimicrobial response effectors related genes) detected were down-regulated in ovarian cancer tissues, while other genes was not statistically significant between ovarian cancer tissues and normal tissues.Conculsions:Taken together, our data, for the first time, indicate that the microbial taxon abundance in ovarian cancer tissues was reduced relative to normal distal fallopian tube tissues. We hypothesize that the microbial dysbiosis, as a risk factor for cancer, may be associated with the initiation and progression of ovarian cancer via influencing and regulating the local immune microenvironment of the tumor. In addition, our results suggest a potential role of cancer microbiota in diagnostic and therapeutic applications for ovarian cancer, for which further detailed research is needed.