Metformin can block precancerous progression to invasive tumors of bladder through inhibiting STAT3-mediated signaling pathways

Table 1 The effects of metformin on the development of MNU-induced rat orthotopic bladder tumors

Macroscopy & microscopy	Control (n = 8)	MNU (n = 8)	MNU + Met (n = 8)	P value
Frequency of tumoringenivity [%(n/n)]	0	100(8/8)	87.5(7/8)	0.5
Areas of tumors [mm²(n)]	0	48.84 ± 17.82(in 8)	17.5 ± 10.88(in 7)	0.0014
Preneoplasic lesions[%(n/n)]
Hyperplasia	0	0	0	1
Dysplasia	0	0	12.5(1/8)	0.302
Neoplasic lesions[%n/n]
Papillary tumor	0	37.5(3/8)	75(6/8)	0.046
Carcinoma in situ	0	75(6/8)	37.5(3/8)	0.046
Infiltrative tumor	0	50(4/8)	0	0.021
Accompanied other pathology [%(n/n)]
Squamous differentiation	0	37.5(3/8)	12.5(1/8)	0.248
Sarcoma	0	12.5(1/8)	0	0.302

P values represent comparion between MNU group and Met group
Note: Multiple lesions at various stages were detected in the same bladders of MNU-induced rats, including papillary tumors, CIS, infiltrative tumors and sarcomas. Upon treatment with metformin, MNU-induced rats were only detected with dysplasia, papillary tumors and CIS. Tumor incidence and tumor size (areas) in MNU-induced rats were reduced upon treatment with metformin

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