Introduction: Trastuzumab, as the gold standard for HER2-positive BC treatment, was the first-line HER2 targeted drug. However, some studies reported patients benefited more from lapatinib and lapatinib plus trastuzumab therapy than standard trastuzumab therapy. This study presents an update of a systematic review and meta-analysis involving comparison of lapatinib and lapatinib plus trastuzumab therapy versus trastuzumab therapy. Aim: We determined whether trastuzumab plus lapatinib or lapatinib therapy is not inferior to trastuzumab therapy in HER2-positive breast cancer patients. Methods: Relevant trials were searched in CNKI, Wanfang, VIP, Sinomed, PubMed, Embase, and Cochrane CENTRAL databases from inception until October 25, 2021. Primary outcomes were OS, DFS/EFS, and PFS while secondary outcomes were pCR (ypT0/is ypN0), pCR (ypT0/is ypN0/+), ORR, DCR, rate of BCS, RFS, cardiac toxicities, and other toxicities. Results: Thirteen randomized controlled trials were included in this study. Trastuzumab combined with lapatinib therapy was found to be superior to standard trastuzumab therapy alone with regard to overall survival, disease-free survival/event-free survival, pathologic complete response (ypT0/is ypN0), pathologic complete response (ypT0/is ypN0/+), recurrence-free survival, higher incidences of diarrhea, and rash/skin toxicity. Lapatinib therapy was established to be inferior to trastuzumab therapy in overall survival, progression-free survival, disease-free survival/event-free survival, pathologic complete response (ypT0/is ypN0) and pathologic complete response (ypT0/is ypN0/+), diarrhea, and rash/skin toxicity and had a low incidence of left ventricular ejection fraction decline. Conclusions: The efficacy of trastuzumab combined with lapatinib therapy is superior to standard trastuzumab therapy alone; however, it has more non-cardiac grade III/IV toxicities. Moreover, the efficacy of lapatinib therapy is inferior to that of standard trastuzumab therapy alone.

Small molecule inhibitors of aurora kinases are currently being investigated in oncology clinical trials. The long-term effects of these inhibitors on proliferating euploid cells have not been adequately studied. We examined the effect of the reversible pan-aurora kinase inhibitor VX-680 on p53-competent human euploid cells. Circumscribed treatment with VX-680 blocked cytokinesis and arrested cells in G1 or a G1-like status. Approximately 70% of proliferatively arrested cells had 4N DNA content and abnormal nuclei. The remaining 30% of cells possessed 2N DNA content and normal nuclei. The proliferative arrest was not due to the activation of the tumor suppressor Rb and was instead associated with rapid induction of the p53–p21 pathway and p16. The induction was particularly evident in cells with nuclear abnormalities but was independent of activation of the DNA damage response. All of these effects were correlated with the potent inhibition of aurora kinase B. After release from VX-680, the cells with normal nuclei robustly resumed proliferation whereas the cells with abnormal nuclei underwent senescence. Irrespective of their nuclear morphology or DNA content, cells pre-treated with VX-680 failed to grow in soft agar or form tumors in mice. Our findings indicate that an intermittent treatment strategy might minimize the on-target side effects of Aurora Kinase B (AURKB) inhibitory therapies. The strategy allows a significant fraction of dividing normal cells to resume proliferation.

Therapeutic targeting of MYC directly has proven difficult, but several means to target MYC indirectly using a synthetic lethal drug approach have been proposed. Synthetic lethal approaches for MYC have sought to take advantage of vulnerabilities MYC imposes related to either metabolic reprogramming, apoptotic signaling or the cycling of cancer cells. Here, we describe in detail the cell division phenotypes induced by a MYC synthetic lethal compound, dimethylfasudil (diMF). DiMF is a known ROCK inhibitor, but structurally related ROCK inhibitors are not synthetic lethal with MYC, so the activity of diMF is not related to blockade of this family of kinases. Instead, this compound induced multiple cell cycle-related liabilities. These included the early mitotic arrest of cycling cells followed by mitotic catastrophe-induced death and the induction of polyploidy in cells that do manage to pass through mitosis. As early as prometaphase, we noted diminished staining for BUB1 kinase, which binds to kinetochores and regulates the mitotic spindle checkpoint and chromosome congression. Kinetochore proteins, such as CENP-F, failed to localize at the metaphase plate, confirming a deficit in centromere assembly. This, presumably, contributed to the development of segregation anomalies in diMF-treated cells. In anaphase cells, the protein regulator of cytokinesis 1 (PRC1), failed to be recruited to the midzone, leading to a cascade of defects that included failed recruitment of the chromosomal passenger protein complex, the centralspindlin complex and polo-like-kinase 1 (PLK1). These observations correlate well with the cell death phenotypes induced by diMF, which may serve as a prototype MYC synthetic lethal compound to explore synthetic lethal therapy or as a scaffold upon which to build superior compounds. The phenotypes described here serve as examples of MYC synthetic lethal drug effects that can be used to explore and maximize drug discovery programs.