Table 1.

Various skin microbiota associated with skin cancers and their proposed mechanisms.

Skin Microbiota	Sample Collection	Proposed Mechanisms
Squamous cell carcinoma
Increased abundance and/or associated with carcinogenesis
Staphylococcus aureus [5,6,7]	Human, skin biopsy, and swab [5] Human, skin swab [6] Human, skin biopsy [7]	Promotes chronic inflammation Associated with increased expression of hBD-2, which causes in the proliferation of tumor cells Results from barrier disruption
Beta HPV types [27,28]	Mouse model, skin biopsy [27] Human, skin biopsy [28]	Act as cocarcinogens, promoting cellular damage under UV irradiation but are not required for the maintenance of SCC
Merkel cell polyomavirus [31]	Human, skin biopsy, blood, mouthwash [31]	Not suggested
Decreased abundance and/or associated with anti-tumor action
Cutibacterium spp.[6]	Human, skin swab	Altered metabolism in SCC might inhibit the growth of Cutibacterium and induce the growth of Staphylococcus aureus
Malassezia spp. [6]	Human, skin swab	Results from skin barrier disruption and decreased sebum availability in SCC Inhibits the growth of S. aureus biofilm formation
Staphylococcus epidermidis [11]		S. epidermidis-derived 6-HAP suppress the synthesis of DNA and exert an antiproliferative effect on tumor cells
Malignant melanoma
Increased abundance and/or associated with carcinogenesis
Corynebacterium spp. [34] Staphylococcus epidermidis [38] Fusobacterium nucleatum [40] High-risk mucosal HPVs [45]	Human, skin swab Pig, skin scrape Human, skin biopsy	Enhance IL-17-dependent pathway Enhances survival of melanocytes via upregulation of TRAF1, CASP14, CASP5, and TP73 during UVB irradiation Inhibits NK cells cytotoxicity through interaction with Fap2 and TIGIT May serve as a cofactor in the development of MM
Decreased abundance and/or associated with anti-tumor action
Cutibacterium acnes [37,38]		Induces Th1 cytokines including −12, TNF-α, and IFN-γ Promotes apoptosis, enhancing the secretion of coproporphyrins, and upregulating TNFα
Staphylococcus epidermidis [11]		S. epidermidis-derived 6-HAP inhibits the growth of B16F10 melanoma cell lines
Cutaneous T cell lymphoma Increased abundance and/or associated with carcinogenesis
Staphylococcus aureus [56,57] Staphylococcus argenteus [61]	Human, skin biopsy, and swab [57] Human, skin swab [56]	Bacterial superantigenic stimuli (TSST-1) and staphylococcus enterotoxin A activate the STAT3 pathway A possible pathogenic role of alpha-hemolysin exotoxin from S. argenteus

Abbreviation: hBD-2, human beta-defensin-2; HPV, human papillomavirus; 6-HAP, 6-N-hydroxyaminopurin; IFN, interferon; SCC, squamous cell carcinoma; TNF, tumor necrosis factor; TSST, toxic shock syndrome toxin -1.