Combating breast cancer using combination therapy with 3 phytochemicals: Piperine, sulforaphane, and thymoquinone.

Despite the significant advances in screening methods for early diagnosis, breast cancer remains a global threat and continues to be the leading cancer diagnosed in women, requiring effective therapy. Currently, combination therapy has become the hallmark of breast cancer treatment due to the high incidence of tumor recurrence and disease progression after monotherapeutic treatments, including surgery, radiotherapy, endocrine therapy, and chemotherapy. Over the past decades, there has been considerable interest in studying the anticancer effect of bioactive phytochemicals from medicinal plants combined with these conventional therapies. The rationale for this type of therapy is to use combinations of drugs that work by different mechanisms, thereby decreasing the likelihood that cancer cells will develop resistance, and also reduce the therapeutic dose and toxicity of single treatments. Three agents have received great attention with regard to their anticancer properties: 1) piperine, a dietary phytochemical isolated from black pepper (Piper nigrum L.) and long pepper (Piper longum L.); 2) sulforaphane, an isothiocyanate mainly derived from cruciferous vegetables; and 3) thymoquinone, the active compound from black seed (Nigella sativa L.). This review focused on the combined effect of these 3 compounds on conventional cancer therapy with the objective of observing enhanced efficacy compared with single treatments. This review also highlights the importance of the nanoformulation of such bioactive phytochemicals that could enhance their bioavailability by providing an efficient targeted delivery system with a reduced systemic dose while resulting in a more efficient dosing at the target site.