Table 1.

The excluded studies and the reasons for their exclusion.

No.	Excluded Study in the Second Phase	The Reason for Its Exclusion
1	Peng et al. [18]	They were solely based on bioinformatics.
2	Qattan et al. [19]
3	Liu et al. [20]
4	Naba et al. [21]	The PD-L1-inhibiting miRs were not adequately investigated.
5	Yang et al. [22]
6	Noman et al. [23]
7	Zhang et al. [24]
8	Nafea et al. [25]
9	Youness et al. [26]
10	Hamed et al. [27]	Pro-PD-L1 miR was studied.
11	Yao et al. [28]	The cross-talk between miR and PD-L1 in macrophages was studied.
12	Rogers, 2018 [29]	The cross-talk between miR and PD-L1 was evaluated only in murine TNBC.

Abbreviations: TNBC: triple-negative breast cancer, and PD-L1: programmed death-ligand 1.