HOXD13 and non-small cell lung carcinoma: The levels of such soluble forms of PD-1 (sPD-1) and PD-L1 (sPD-L1) have been found to be related to the progression and prognosis of PD-1 blockade therapy, but only a limited number of such studies has focused on advanced solid tumors other than NSCLC and melanoma (11).