Figure 4 presents some Hsp40 family members which are regarded as either tumor suppressors or tumor promoters. Given the roles of Hsp40 family members in breast cancer, it has also been demonstrated that they are involved in the pharmacodynamic effects of chemotherapy drugs. R115777, a farnesyltransferase inhibitor, suppressed the production of pro-angiogenic growth factors in BT-474 and MDA-MB-231 breast cancer cells by inhibiting the activities of DNAJA1 [50]. Here, DNAJB1 is linked to breast cancer.