Neonatal Nav1.5 (nNav1.5) is the alternative splice variant of Nav1.5 and it has been widely associated with the progression of breast cancer. The immunological context of nNav1.5 with respect to breast cancer metastases remains unexplored. The presence of antibodies against nNav1.5 may highlight the immunogenicity of nNav1.5. Hence, the aim of the present study was to detect the presence of antineonatal Nav1.5 antibodies (antinNav1.5-Ab) in the serum of patients with breast cancer and to elucidate the effects of breast cancer therapy on its expression. A total of 32 healthy female volunteers and 64 patients with breast cancer were randomly recruited into the present study as the control and breast cancer group, respectively. Patients with breast cancer were divided equally based on their pre- and ongoing-treatment status. Serum samples were tested with in-house indirect enzyme-linked immunosorbent assay (ELISA) to detect antinNav1.5-Ab, CD25 (T regulatory cell marker) using an ELISA kit and Luminex assay to detect the expression of metastasis-associated cytokines, such as vascular endothelial growth factor (VEGF), interleukin (IL)-6, IL-10, IL-8, chemokine (C-C motif) ligand 2 and tumor necrosis factor-alpha (TNF-α) The mean difference in the expression of antinNav1.5-Ab among the three groups (control, pretreatment and ongoing-treatment) was significant (P=0.0005) and the pretreatment breast cancer group exhibited the highest expression. The concentration of CD25 was highest in the pretreatment breast cancer group compared with the control and ongoing-treatment groups. There was a significant positive correlation between antinNav1.5-Ab and IL-6 in the pretreatment group (r=0.7260; P=0.0210) and a significant negative correlation between antinNav1.5-Ab and VEGF in the ongoing-treatment group (r=−0.842; P-value=0.0040). The high expression of antinNav1.5-Ab in the pretreatment group was in accordance with the uninterrupted presence of metastasis and highlighted the immunogenicity of nNav1.5 whereas the low expression of antinNav1.5-Ab in the ongoing-treatment group reflected the efficacy of breast cancer therapy in eliminating metastases. The augmented manifestation of T regulatory cells in the pretreatment group highlighted the functional role of nNav1.5 in promoting metastasis. The parallel expression of antinNav1.5-Ab with the imbalanced expression of cytokines promoting metastasis (IL-8, IL-6 and TNF-α) and cytokines that prevent metastasis (IL-10) indicated the role of nNav1.5 in breast cancer growth. The expression of antinNav1.5-Ab in accordance to the metastatic microenvironment indicates the immunogenicity of the protein and highlights the influence of breast cancer therapy on its expression level.

Oestrogen receptor (ER)-positive breast cancer is one of the common forms of breast cancer affecting women worldwide. ER-positive breast cancer patients are subjected to anti-oestrogen therapy such as selective oestrogen receptor modulator (SERM) and aromatase inhibitors (AIs). Recently, the emergence of resistance to anti-oestrogen treatment is under intensive focus. The different mechanisms postulated to explain the occurrence of resistance in ER-positive breast cancer treatment include the loss of ER function and the crosstalk between signalling pathways in cancer cells. Recent literature highlighted that the cholesterol biosynthesis pathway acts as a novel mechanism underlying resistance to oestrogen deprivation. The present study aimed to highlight the role of cholesterol biosynthesis in anti-oestrogen treatment resistance, putatively suggesting an alternative plant-based treatment using andrographolide from Andrographis paniculata. The hypolipidaemic effect of andrographolide can be utilised to prevent the resistance in the treatment of ER-positive breast cancer contributed by cholesterol biosynthesis.

Background: The study was aimed to elucidate the influence of passage number of 4T1 cells for the development of the ideal tumour model. Methods: A total of 24 female BALB/c mice was divided equally into three groups: i) control (phosphate buffered saline [PBS] only); ii) group A (subjected to 4T1 cells of passage number 9) and iii) group B (subjected to 4T1 cells of passage number 10). The injections were introduced at the 3rd mammary pad of the mice. The net volume of the tumours was examined. Histopathological analysis was conducted to compare the extent of metastasis in the different groups of mice. Results: Group B had a higher net volume of 4T1 tumour as compared to group A (P = 0.042). The coefficient of variation in the net volume of 4T1 tumour for group A was higher (135.3%) as compared to group B (40.79%). Group A only exhibited metastasis on the lungs, liver and spleen whereas group B showed metastasis to the heart, spleen, lungs and liver. Conclusion: The use of 4T1 cells from passage number 10 is more ideal for the development of 4T1 tumour.

Nav1.5 is one of the nine voltage-gated sodium channel-alpha subunit (VGSC-α) family members. The Nav1.5 channel typically carries an inward sodium ion current that depolarises the membrane potential during the upstroke of the cardiac action potential. The neonatal isoform of Nav1.5, nNav1.5, is produced via VGSC-α alternative splicing. nNav1.5 is known to potentiate breast cancer metastasis. Despite their well-known biological functions, the immunological perspectives of these channels are poorly explored. The current review has attempted to summarise the triad between Nav1.5 (nNav1.5), breast cancer, and the immune system. To date, there is no such review available that encompasses these three components as most reviews focus on the molecular and pharmacological prospects of Nav1.5. This review is divided into three major subsections: (1) the review highlights the roles of Nav1.5 and nNav1.5 in potentiating the progression of breast cancer, (2) focuses on the general connection between breast cancer and the immune system, and finally (3) the review emphasises the involvements of Nav1.5 and nNav1.5 in the functionality of the immune system and the immunogenicity. Compared to the other subsections, section three is pretty unexploited; it would be interesting to study this subsection as it completes the triad.

Neonatal Nav1.5 (nNav1.5) has been known to potentiate breast cancer (BCa) metastasis. The detection of anti-nNav1.5 antibodies (anti-nNav1.5-Ab) reflects the immunogenicity of nNav1.5. However, the presences of circulating nNav1.5 antigen and anti-nNav1.5-Ab in the context of BCa metastasis have not been explored yet. Therefore, the study has attempted to conduct such an investigation using both blood samples from 4T1 orthotopic mice and BCa patients. In the preclinical study, forty female BALB/c mice were divided into three groups: 4T1 orthotopic BCa mice (n=17), control mice (n=20) and positive control mice (n=3). After tumour development, the mice were sacrificed to obtain target organs, whole blood, and serum. Histopathology, cytokine analyses, real-time PCR, and indirect ELISA were performed. Histopathology and cytokine analyses showed the establishment of metastasis in 4T1 orthotopic mice. The concentration of vascular endothelial growth factor (VEGF) was significantly higher in the 4T1 orthotopic mice (P<0.0001****). Circulating nNav1.5 antigen and anti-nNav1.5-Ab were detected in 4T1 orthotopic mice, using real-time PCR and indirect ELISA, respectively. Furthermore, there was an inverse relationship between anti-nNav1.5-Ab and the total metastatic foci (P=0.0485*, r=-0.7306). In the clinical study, 32 BCa patients were grouped based on their stages: early-invasive (n=15) and advanced (n=17) stages. Approximately 3 mL of blood was withdrawn, and only indirect ELISA was conducted. The clinical study showed that BCa patients of advanced-stages portrayed higher expression of anti-nNav1.5-Ab compared to early stages of BCa (P =0.0110*). In conclusion, the detection of nNav1.5 antigen and anti-nNav1.5-Ab was consistent with the presence of BCa metastasis.