CONFIDENTIAL COMMENTS TO EDITOR I recommend the editor to publish the article with major revisions, since it is an interesting paper, which adds knowledge in its specific field, well organized and logically developed. The writing style is not satisfactory or easy to understand, so I recommend a general grammar review and I suggest, right now, some specific major revisions (listed in the window to the authors). COMMENTS TO AUTHORS Avoid the excessive use of the first-person plural “we” or possessive pronoun “our” which could be replaced by expressions like “In this study…” or “The present work. Section Abstract: Rephrase the sentence “In many malignant tumors including oral cancer, hypoxia inducible factor (HIF) is involved in tumor growth and metastasis and upregulated by hypoxia.” Rephrase the sentence “we investigated the correlation between prognosis in OSCC patients and HIF expression and conducted a meta-analysis of relevant publications searched in searches of the Web of Science, PubMed and ISI Web of Knowledge databases”. Avoid starting the sentences with “and”. Please verify if the abstract text is finished, as well as key words; review punctuation.

Section Introduction: Review the first two sentences since both refer the frequency, appearing to be redundant. What do authors mean with “original field”? Start following sentence with a connecting element, like “Also”, e.g. “Also, oral cancer patients…” Rewrite the sentence “Recently, some studies also show...”, using the past tense. Rewrite and introduce commas in the sentences: “Therefore, in this systematic meta-analysis of the relevant publications, identified in searches of publically available databases, we try to evaluate the prognostic significance of HIFs in OSCC.” Enrich this section clarifying, briefly, how hypoxia could promote tumour progression and resistance to radiotherapy and chemotherapy, referring the mechanisms (not the consequences already indicating in discussion section e.g. angiogenesis, metastasis…). Why this neoplastic cells, in hypoxic microenvironments, are still growing, conducting to the tumour progression?

Section Materials and Methods: Pay attention to the format and verify the correct way to mention the study authors. Rewrite the sentence ”There were 0 to 9 stars which were designated as the lowest to highest quality, and according to this scale studies awarded more than 6 stars including 6 stars, were regarded to be of high quality”.

Section Results and Discussion: Introduce commas in the sentences: “Table 1 shows the methodological quality of the included studies, according to the Newcastle–Ottawa quality assessment scale.” “Therefore, hypoxia is a prognostic factor for a variety of cancers, including OSCC. HIF-1α and HIF-2α are two of the most significant transcription factors, mediating the cellular response to hypoxia [21].” Avoid the excessive use of the expression “meta-analysis”. The numbers indicating references are linked to the last word or with space e.g. angiogenesis[24-27]. Some… angiogenesis [28]…”; verify the correct way.

Section Conclusions: Introduce comma, since some sentences are very large and unbroken.

Please disclose any competing interests you may have regarding this paper: I have no competing interests to declare.