Table 1.

Basic information about the 45 studies that met the inclusion criteria for this systematic review.

References	Tumor type	Tumor site	Number of samples	Sample	Species
Stasikowska-Kanicka et al. (20)	SCC	Oral cavity (floor of the mouth)	78 Patients (41 poor prognosis, 37 better prognosis) 18 Controls (normal mucosa)	Tumor	Human
Hussaini et al. (31)	SCC	Oral cavity	25 Patients 12 Controls (inflammatory hyperplastic tissue)	Tumor	Human
Ihara et al. (17)	SCC	Oral cavity, oropharynx, nasopharynx, larynx, maxillary sinus	46 SCC 23 Controls	Blood	Human
Ma et al. (32)	SCC	HNC	Human samples: 43 Normal 48 Dysplastic 165 Primary HNSCC 12 Recurrent HNSCC 17 HNSCC with induction chemotherapy Murine samples: 6 WT normal tongue 6 WT tumor bearing mice 6 KO tumor bearing mice	Tumor	Human/Murine
Zhou et al. (33)	SCC	Tongue	46 SCC 46 Paired tumor adjacent non-neoplastic tongue epithelium 20 Metastasis lymph nodes 20 Paired normal cervical lymph nodes	Tumor	Human
Nguyen et al. (25)	SCC	Larynx, oral cavity, oropharynx, hypopharynx	278 SCC	Tumor	Human
Miki et al. (34)	SCC	Tongue	20 Controls 20 4NQO 40 4NQO treated with COX-2 inhibitor	Tumor	Murine
da Cunha Filho et al. (35)	SCC	Low lip	50 Patients, 10 microscopic fields per patient	Tumor	Human
Montler et al. (36)	SCC	Base of the tongue, tonsil, oropharynx, nasal, oral tongue, mandibular gingiva, maxillary sinus, larynx, floor of the mouth	29 Patients	Tumor blood	Human
Takahashi et al. (37)	SCC	Oral cavity, oropharynx, hypopharynx, larynx, paranasal cavity	20 Healthy controls 44 Patients treated with surgery/radio/radio-chemotherapy 16 Chemotherapy	Blood	Human
Jie et al. (18)	SCC	Oral cavity, oropharynx, larynx, hypopharynx	22 Patients treated with cetuximab plus cisplatin/paclitaxel/radiotherapy followed by 6 months of maintenance single agent cetuximab 18 Patients received single-agent cetuximab	Tumor blood	Human
Partlova et al. (38)	SCC	Tongue, tonsil, larynx, verbal base, hypopharynx, Gl. submandibularis, floor of mouth	54 Patients	Tumor blood	Human
Wolf et al. (29)	SCC	Oral cavity: tongue, upper alveolus, floor of mouth, hard palate, buccal mucosa, and retromolar	39 Patients	Blood	Human
Sun et al. (39)	SCC	Oral cavity, hypopharynx, nasopharynx, oropharynx, larynx	112 Patients 31 Healthy donors	Blood	Human
Schipmann et al. (40)	SCC	Oral cavity and skin	FOXP3 mRNA expression: 13 Cutaneous cSCC 8 Oral SCC 14 SCC metastases Immunohistochemistry: 10 Cutaneous SCC 8 Oral SCC 4 SCC metastases 10 Normal skin control Cell lines: Primary human adult skin fibroblasts Human squamous cell carcinoma cell line	Tumor	Human
Lim et al. (23)	SCC	Oral cavity	39 Patients 24 Controls	Blood	Human
Hanakawa et al. (16)	SCC	Tongue	34 Patients	Tumor	Human
Ward et al. (28)	SCC	Oropharynx	149 HPV+ 121 HPV–	Tumor	Human
Lukesova et al. (24)	SCC	Oral cavity, oropharynx	60 Patients	Blood	Human
Zhao et al. (41)	SCC	Tongue	16 Controls 32 4NQO	Tumor blood	Rat
Jie et al. (42)	SCC	Oral cavity, oropharynx	27 Patients	Tumor blood	Human
Park et al. (26)	SCC	Tonsil	79 Patients	Tumor	Human
Weed et al. (43)	SCC	Tongue	49 Patients	Tumor	Human
Drennan et al. (44)	SCC	Oropharynx, larynx	14 Controls 39 Patients	Blood	Human
Bron et al. (22)	SCC	Oral cavity, oropharynx, hypopharynx, larynx	35 Patients	Tumor blood	Human
Judd et al. (19)	SCC	Oral cancer cell line injected in flank	Not disclosed in manuscript	Tumor	Murine
Gaur et al. (45)	SCC	Oral cavity	45 Patients 40 Controls	Blood	Human
Wansom et al. (27)	SCC	Oropharynx	46 Patients	Tumor blood	Human
Wild et al. (46)	SCC	Oral cavity, pharynx, larynx	35 Patients 17 Controls	Tumor blood	Human
Näsman et al. (47)	SCC	Tonsil	31 HPV+ with a good clinical outcome 21 HPV+ with a poor clinical outcome 11 HPV– with a good clinical outcome 20 HPV– with a poor clinical outcome	Tumor	Human
Lee et al. (48)	SCC	Oral cavity	38 Patients 5 Controls	Tumor blood	Human
Schuler et al. (49)	SSC	Oral cavity, pharynx, larynx	9 Patient samples for dendritic cell culture 13 Patient samples for Treg frequency	Blood	Human
Alhamarneh et al. (50)	SCC	Larynx, oropharynx, oral cavity, hypopharynx, nasal cavity, lymph node metastasis, unknown primary site	107 Patients pretreatment 43 4–6 weeks posttreatment 40 Controls	Blood	Human
Al-Qahtani et al. (51)	SCC	Oral cavity	34 Patients	Tumor	Human
Tominaga et al. (52)	MM	Oral cavity	7 Patients 10 Controls	Tumor Blood	Canine
Horiuchi et al. (53)	MM	Oral cavity	15 Patients 10 Controls	Blood	Canine
Schott et al. (54)	SCC	Epipharynx, oropharynx, hypopharynx, larynx, oral cavity	16 Patients with active disease 16 Patients with no evidence of disease 21 Controls	Blood	Human
Gasparoto et al. (55)	SCC	Oral cavity, lip	9 Patients 10 Controls	Tumor Blood	Human
Boucek et al. (15)	SCC	Oral cavity, hypopharynx, larynx	112 Patients 20 Controls	Blood	Human
Distel et al. (56)	SCC	Oral cavity, hypopharynx, oropharynx	62 Low-risk group patients with early disease 53 High-risk group inoperable patients with advanced disease	Tumor	Human
Schwarz et al. (57)	SCC	Oral cavity	15 Patients 15 Controls	Tumor	Human
Bergmann et al. (58)	SCC	HNSCC cell lines from primary tumors	Cell culture of irradiated HNSCC cell lines from primary tumors with blood samples from 10 healthy donors	Blood	Human
Chikamatsu et al. (59)	SCC	Oral cavity, oropharynx, hypopharynx, larynx, paranasal sinuses	43 Patients 24 Controls	Blood	Human
Badoual et al. (21)	SCC	Oral cavity, oropharynx, hypopharynx	84 Patients	Tumor	Human
Schaefer et al. (60)	SCC	Larynx, oral cavity, pharynx, hypopharynx	24 Patients 17 Controls	Blood	Human

SCC, Squamous Cell Carcinoma; MM, Multiple Myeloma; HNC, Head and Neck Cancer; HNSCC, Head and Neck Squamous Cell Carcinoma.