ACP1 and breast carcinoma: On the other hand, based on the key role of low-molecular-weight protein tyrosine phosphatase slow isoform (LMW-PTPsi) in the interplay between tumor cells and osteoclasts during bone metastases, it was seen that the knockdown of LMW-PTP and its slow isoform did not decrease IL-6 expression in breast cancer cells [67].