The oral tyrosine kinase inhibitors lapatinib and sunitinib: new opportunities for the treatment of brain metastases from breast cancer?

Structural binding site comparisons reveal Crizotinib as a novel LRRK2 inhibitor

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a frequent cause of autosomal dominant Parkinson’s disease (PD) and have been associated with familial and sporadic PD. Reducing the kinase activity of LRRK2 is a promising therapeutic strategy since pathogenic mutations increase the kinase activity. Several small-molecule LRRK2 inhibitors are currently under investigation for the treatment of PD. However, drug discovery and development are always accompanied by high costs and a risk of late failure. The use of already approved drugs for a new indication, which is known as drug repositioning, can reduce the cost and risk.

In this study, we applied a structure-based drug repositioning approach to identify new LRRK2 inhibitors that are already approved for a different indication. In a large-scale structure-based screening, we compared the protein–ligand interaction patterns of known LRRK2 inhibitors with protein–ligand complexes in the PDB. The screening yielded 6 drug repositioning candidates. Two of these candidates, Sunitinib and Crizotinib, demonstrated an inhibition potency (IC50) and binding affinity (K_d) in the nanomolar to micromolar range. While Sunitinib has already been known to inhibit LRRK2, Crizotinib is a novel LRRK2 binder.

Our results underscore the potential of structure-based methods for drug discovery and development. In light of the recent breakthroughs in cryo-electron microscopy and structure prediction, we believe that structure-based approaches like ours will grow in importance.

Activation of Neuregulin 1/ErbB Signaling Is Involved in the Development of TOCP-Induced Delayed Neuropathy

Organophosphate-induced delayed neuropathy (OPIDN) is characterized by progressive axonal degeneration and demyelination of the spinal cord and sciatic nerves. The neuregulin 1/epidermal growth factor receptor (ErbB) signaling pathway is crucial for axonal myelination. In this study, we investigated whether the neuregulin 1/ErbB signaling pathway mediated the progression of OPIDN. Adult hens were given tri-o-cresyl phosphate (TOCP), a typical neuropathic organophosphorus compound, to induce OPIDN. The ErbB inhibitor lapatinib was administered to hens 4 h prior to and 4 days after TOCP exposure. The neuregulin 1/ErbB signaling pathway was examined for their role in maintaining spinal cord and sciatic nerve fiber integrity. Schwann cell line sNF96.2 was used as the in vitro cell model. The in vivo results showed that TOCP (750 mg/kg body weight, p.o.) induced prominent ataxia and significant axon degeneration in the spinal cord and sciatic nerves. Lapatinib (25 mg/kg body weight, p.o.) treatment attenuated OPIDN clinically and histopathlogically and partially prevented the TOCP-induced activation of neuregulin 1/ErbB signaling pathway. Lapatinib also prevented the TOCP-induced inhibition of neuropathy target esterase (NTE), a key enzyme during the development of OPIDN, and the disturbed metabolism of phosphatidylcholine in sciatic nerves. In addition, lapatinib was shown, in vitro, to protect sNF96.2 cells from TOCP-induced dedifferentiation through neuregulin 1/ErbB signaling. Our results suggest that neuregulin 1/ErbB, through regulation of NTE activity in the peripheral nervous system, mediates the progression of OPIDN. Thus, this signal may serve as a potential target for the treatment of OPIDN.

Sunitinib produces neuroprotective effect via inhibiting nitric oxide overproduction

BACKGROUND

Sunitinib is an inhibitor of the multiple receptor tyrosine kinases (RTKs) for cancer therapy. Some sunitinib analogues could prevent neuronal death induced by various neurotoxins. However, the neuroprotective effects of sunitinib have not been reported.

METHODS

Cerebellar granule neurons (CGNs) and SH-SY5Y cells were exposed to low-potassium and MPP(+) challenges, respectively. MTT assay, FDA/PI staining, Hoechst staining, DAF-FM, colorimetric nitric oxide synthase (NOS) activity assay, and Western blotting were applied to detect cell viability, NO production, NOS activity, and neuronal NOS (nNOS) expression. Short hairpin RNA was used to decrease nNOS expression. In vitro NOS enzyme activity assay was used to determine the direct inhibition of nNOS by sunitinib.

RESULTS

Sunitinib prevented low-potassium-induced neuronal apoptosis in CGNs and MPP(+) -induced neuronal death in SH-SY5Y cells. However, PTK787, another RTK inhibitor, failed to decrease neurotoxicity in the same models. Sunitinib reversed the increase in NO levels, NOS activity, and nNOS expression induced by low potassium or MPP(+) . Knockdown of nNOS expression partially abolished the neuroprotective effects of sunitinib. Moreover, sunitinib directly inhibited nNOS enzyme activity.

CONCLUSIONS

Sunitinib exerts its neuroprotective effects by inhibiting NO overproduction, possibly via the inhibition of nNOS activity and the decrease in nNOS expression.

Phase I trial combining temozolomide plus lapatinib for the treatment of brain metastases in patients with HER2-positive metastatic breast cancer: the LAPTEM trial

BACKGROUND

Brain metastases (BMs) pose a clinical challenge in breast cancer (BC). Lapatinib or temozolomide showed activity in BM. Our study assessed the combination of both drugs as treatment for patients with HER2-positive BC and BM.

METHODS

Eighteen patients were enrolled, with sixteen of them having recurrent or progressive BM. Any type of previous therapy was allowed, and disease was assessed by gadolinium (Gd)-enhanced magnetic resonance imaging (MRI). The primary end points were the evaluation of the dose-limiting toxicities (DLTs) and the determination of the maximum-tolerated dose (MTD). The secondary end points included objective response rate, clinical benefit and duration of response.

RESULTS

The lapatinib-temozolomide regimen showed a favorable toxicity profile because the MTD could not be reached. The most common adverse events (AEs) were fatigue, diarrhea and constipation. Disease stabilization was achieved in 10 out of 15 assessable patients. The estimated median survival time for the 16 patients with BM reached 10.94 months (95% CI: 1.09-20.79), whereas the median progression-free survival time was 2.60 months [95% confidence interval (CI): 1.82-3.37].

CONCLUSIONS

The lapatinib-temozolomide combination is well tolerated. Preliminary evidence of clinical activity was observed in a heavily pretreated population, as indicated by the volumetric reductions occurring in brain lesions.

Multiple brain metastases - current management and perspectives for treatment with electrochemotherapy

Background

Due to the advanced oncological treatments of cancer, an overall increase in cancer incidence, and better diagnostic tools, the incidence of brain metastases is on the rise. This review addresses the current treatment options for patients with multiple brain metastases, presenting electrochemotherapy (ECT) as one of the new experimental treatments for this group of patients.

Conclusions

Neurosurgery, stereotactic surgery, and whole-brain radiotherapy are the evidence-based treatments that can be applied for patients with multiple brain metastases. Treatment with chemotherapy and molecularly targeted agents may also be warranted. Several experimental treatments are emerging, one of which is ECT, an effective cancer treatment comprising electric pulses given by electrodes in the tumor tissue, causing electroporation of the cell membrane, and thereby augmenting uptake and the cytotoxicity of the chemotherapeutic drug bleomycin by 300 times. Preclinical data are promising and the first patient has been treated in an ongoing clinical trial for patients with brain metastases. Perspectives for ECT in the brain include treatment of primary and secondary brain tumors as well as soft tissue metastases elsewhere.

Anti-tumour activity of 4-(4-fluorophenyl)amino-5,6,7-trimethoxyquinazoline against tumour cells in vitro

In order to create novel, potent and selective anti-cancer agents, the action of 4-(4-fluorophenyl)amino-5,6,7-trimethoxyquinazoline (compound 1018) on 10 different kinds of tumour cells were assayed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide]. It possesses a broad spectrum of anti-cancer activity. The mechanism of action of 4-(4-fluorophenyl)amino-5,6,7-trimethoxyquinazoline (hereafter referred to as compound 1018) against tumour cells was studied in androgen-independent prostate cancer PC-3 cells by microscopic observation, LDH (lactate dehydrogenase) release assay and Western blotting. Its activity was dose-dependent, with an IC50 of 13.0±1.4 μM after 72 h treatment. Microscopy and LDH release assay indicated that the effect was through anti-proliferation rather than cytotoxicity. Western blot analysis also showed that treatment of cells with 50 μM compound 1018 for 30 min almost completely inhibited EGF (epidermal growth factor)-induced phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2), which suggests that its anti-proliferative effect is largely associated due to ERK1/2 activation being inhibited. Thus compound 1018 is a potential anti-cancer agent.

Molecular aspects of breast cancer metastasis to the brain

Our knowledge of the biology underlying the development of brain metastases (BM) from breast cancer has improved over the last decade due to large clinical epidemiological studies, animal models of metastasis, and the use of high-resolution gene expression profiling technologies. However, there are still major gaps in our understanding of the mechanisms utilized by breast cancer cells to colonize the brain microenvironment, thus our arsenal of therapies remains relatively nonspecific, and the prognosis for breast cancer patients with BM remains poor. Additional insights into these mechanisms are necessary to facilitate the development of new preventive and curative therapeutic regimens to block this fatal disease. This paper aims to provide a general overview for the readers of what has been achieved in this field of research and its translation into clinical practice to date and to highlight exciting new areas of research that promise to inform the development of new targeted therapies for BM.