Microtubule-Associated Protein Tau, α-Tubulin and βIII-Tubulin Expression in Breast Cancer

RAD6 inhibition enhances paclitaxel sensitivity of triple negative breast cancer cells by aggravating mitotic spindle damage

Background

Paclitaxel (PTX), a first-line therapy for triple negative breast cancers (TNBC) induces anti-tumor activity by microtubule stabilization and inhibition of cell division. Its dose-limiting toxicity and short half-life, however, pose clinical challenges underscoring the need for strategies that increase its efficiency. RAD6, a E2 ubiquitin conjugating enzyme, is associated with centrosomes at all phases of cell cycle. Constitutive overexpression of the RAD6B homolog in normal breast cells induces centrosome amplification and multipolar spindle formation, indicating its importance in centrosome regulation.

Methods

TNBC centrosome numbers were scored by pericentrin immunostaining. PTX sensitivities and interactions with SMI#9, a RAD6-selective small molecule inhibitor, on TNBC cell survival were analyzed by MTT and colony forming assays and an isogenic MDA-MB-468 TNBC model of PTX resistance. The molecular mechanisms underlying PTX and SMI#9 induced cytotoxicity were determined by flow cytometry, immunoblot analysis of cyclin B1 and microtubule associated protein TAU, and dual immunofluorescence staining of TAU and α-tubulin.

Results

Our data show aberrant centrosome numbers and that PTX sensitivities are not correlated with TNBC BRCA1 status. Combining PTX with SMI#9 synergistically enhances PTX sensitivities of BRCA1 wild-type and mutant TNBC cells. Whereas SMI#9/PTX combination treatment increased cyclin B1 levels in MDA-MB-468 cells, it induced cyclin B1 loss in HCC1937 cells with accumulation of reproductively dead giant cells, a characteristic of mitotic catastrophe. Cell cycle analysis revealed drug-induced accumulation of tetraploid cells in S and G2/M phases, and robust increases in cells with 4 N DNA content in HCC1937 cells. TAU overexpression is associated with reduced PTX efficacy. Among the six TAU isoforms, both SMI#9 and PTX downregulated 1N3R TAU in MDA-MB-468 and HCC1937 cells, suggesting a common mechanism of 1N3R regulation. Dual TAU and α-tubulin immunostaining showed that SMI#9 induces monopolar mitotic spindles. Using the isogenic model of PTX resistance, we show that SMI#9 treatment restores PTX sensitivity.

Conclusions

These data support a common mechanism of microtubule regulation by SMI#9 and PTX and suggest that combining PTX with RAD6 inhibitor may be beneficial for increasing TNBC sensitivities to PTX and alleviating toxicity. This study demonstrates a new role for RAD6 in regulating microtubule dynamics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10119-z.

Tubulin Isotypes: Emerging Roles in Defining Cancer Stem Cell Niche

Although the role of microtubule dynamics in cancer progression is well-established, the roles of tubulin isotypes, their cargos and their specific function in the induction and sustenance of cancer stem cells (CSCs) were poorly explored. But emerging reports urge to focus on the transport function of tubulin isotypes in defining orchestrated expression of functionally critical molecules in establishing a stem cell niche, which is the key for CSC regulation. In this review, we summarize the role of specific tubulin isotypes in the transport of functional molecules that regulate metabolic reprogramming, which leads to the induction of CSCs and immune evasion. Recently, the surface expression of GLUT1 and GRP78 as well as voltage-dependent anion channel (VDAC) permeability, regulated by specific isotypes of β-tubulins have been shown to impart CSC properties to cancer cells, by implementing a metabolic reprogramming. Moreover, βIVb tubulin is shown to be critical in modulating EphrinB1signaling to sustain CSCs in oral carcinoma. These tubulin-interacting molecules, Ephrins, GLUT1 and GRP78, are also important regulators of immune evasion, by evoking PD-L1 mediated T-cell suppression. Thus, the recent advances in the field implicate that tubulins play a role in the controlled transport of molecules involved in CSC niche. The indication of tubulin isotypes in the regulation of CSCs offers a strategy to specifically target those tubulin isotypes to eliminate CSCs, rather than the general inhibition of microtubules, which usually leads to therapy resistance.

Influence of Paclitaxel and Doxorubicin Therapy of ßIII-Tubulin, Carbonic Anhydrase IX, and Survivin in Chemically Induced Breast Cancer in Female Rat

Breast cancer is the most common cancer in females. The aim of this study was to determine the effect of paclitaxel (PTX) and doxorubicin (DOX) therapy on the βIII-tubulin, carbonic anhydrase IX (CA IX), and survivin expression in chemically-induced rat mammary tumors. Animals with induced mammary carcinogenesis were randomly divided into treatment groups and an untreated group. The total proportion of tumors, the proportion of carcinoma in situ (CIS), and invasive carcinoma (IC) were evaluated. Protein expression in tumor tissue was determined using IHC. Statistical analysis of the data, evaluated by Fisher-exact test and unpaired t-test. Significantly increased levels of proteins in the tumor cells were confirmed using the IHC method for all studied proteins. The expression of βIII-tubulin, CA IX, and survivin increased significantly after treatment with both cytostatics (PTX and DOX). Depending on the type of tumor, a significant increase in all proteins was observed in IC samples after PTX treatment, and CA IX expression after DOX treatment. In CIS samples, a significant increase of βIII-tubulin and survivin expression was observed after a DOX treatment. The results suggest that βIII-tubulin, survivin, and CA IX may be significant drug resistance markers and the clinical regulation of their activity may be an effective means of reversing this resistance.

Increased expression of αTubulin is associated with poor prognosis in patients with pancreatic cancer after surgical resection

Background

αTubulin, the essential orchestrator of cytoskeletal protein polymers, critical for cell growth and division, motility, signaling development and maintenance of cell shape, plays vital roles in the oncogenesis and progression of various types of cancer, but its role in prognosis of pancreatic cancer patients remains unknown. The aim of this study was to investigate its prognostic value in patients with pancreatic cancer after surgical resection.

Results

αTubulin expression in pancreatic cancer was significantly associated with N classification (p = 0.013) and TNM stage (p = 0.025). Increased expression of αTubulin in tumoral tissue was associated with decreased overall survival rate (p = 0.002). Multivariate Cox regression analysis suggested that αTubulin expression was an independent prognostic indicator for pancreatic cancer except for T and N classification (p = 0.002). Using multivariate analysis, αTubulin expression, CA19-9, and N classification were selected to generate the nomogram to predict the 1-year and 3-year overall survival. The c-index of this model was 0.692. The calibration curve for probability of survival showed good agreement between prediction by nomogram and actual observation.

Methods

αTubulin expression was evaluated by tissue microarrays from 124 pancreatic cancer patients and statistically assessed for correlations with the clinical profiles and the prognosis of the patients with pancreatic cancer. The prognostic nomogram was designed to predict 1-year and 3-year overall survival probability.

Conclusions

αTubulin expression might be an independent prognostic factor for pancreatic cancer after surgical resection and could potentially be a high-priority therapeutic target. Incorporating αTubulin expression into CA19-9 and N classification can provide a good prognostic model.

A strategy to identify housekeeping genes suitable for analysis in breast cancer diseases

BACKGROUND

The selection of suitable internal control genes is crucial for proper interpretation of real-time PCR data. Here we outline a strategy to identify housekeeping genes that could serve as suitable internal control for comparative analyses of gene expression data in breast cancer cell lines and tissues obtained by high throughput sequencing and quantitative real-time PCR (qRT-PCR).

METHODS

The strategy proposed includes the large-scale screening of potential candidate reference genes from RNA-seq data as well as their validation by qRT-PCR, and careful examination of reference data from the International Cancer Genome Consortium, The Cancer Genome Atlas and Gene Expression Omnibus repositories.

RESULTS

The identified set of reference genes, also called novel housekeeping genes that includes CCSER2, SYMPK, ANKRD17 and PUM1, proved to be less variable and thus potentially more accurate for research and clinical analyses of breast cell lines and tissue samples compared to the traditional housekeeping genes used to this end.

DISCUSSION

These results highlight the importance of a massive evaluation of housekeeping genes for their relevance as internal control for optimized intra- and inter-assay comparison of gene expression.

CONCLUSION

We developed a strategy to identify and evaluate the significance of housekeeping genes as internal control for the intra- and inter-assay comparison of gene expression in breast cancer that could be applied to other tumor types and diseases.

HE4 promotes collateral resistance to cisplatin and paclitaxel in ovarian cancer cells

Background

Chemotherapy resistance presents a difficult challenge in treating epithelial ovarian cancer patients, particularly when tumors exhibit resistance to multiple chemotherapeutic agents. A few studies have shown that elevated serum levels of the ovarian cancer biomarker HE4 correlate with tumor chemoresistance, response to treatment, and survival. Here, we sought to confirm our previous results that HE4 contributes to collateral resistance to cisplatin and paclitaxel in vitro and uncover factors that may contribute to HE4-mediated chemoresistance.

Methods

MTS assays and western blots for cleaved PARP were used to assess resistance of HE4-overexpressing SKOV3 and OVCAR8 clones to cisplatin and paclitaxel. CRISPR/Cas technology was used to knockdown HE4 in HE4-overexpressing SKOV3 cells. A microarray was conducted to determine differential gene expression between SKOV3 null vector-transfected and HE4-overexpressing clones upon cisplatin exposure, and results were validated by quantitative RT-PCR. Regulation of mitogen activated protein kinases (MAPKs) and tubulins were assessed by western blot.

Results

HE4-overexpressing SKOV3 and OVCAR8 clones displayed increased resistance to cisplatin and paclitaxel. Knockdown of HE4 in HE4-overexpressing SKOV3 cells partially reversed chemoresistance. Microarray analysis revealed that HE4 overexpression resulted in suppression of cisplatin-mediated upregulation of EGR1, a MAPK-regulated gene involved in promoting apoptosis. Upregulation of p38, a MAPK activated in response to cisplatin, was suppressed in HE4-overexpressing clones. No differences in extracellular signal-regulated kinase (ERK) activation were noted in HE4-overexpressing clones treated with 25 μM cisplatin, but ERK activation was partially suppressed in HE4-overexpressing clones treated with 80 μM cisplatin. Furthermore, treatment of cells with recombinant HE4 dramatically affected ERK activation in SKOV3 and OVCAR8 wild type cells. Recombinant HE4 also upregulated α-tubulin and β-tubulin levels in SKOV3 and OVCAR8 cells, and microtubule associated protein tau (MAPT) gene expression was increased in SKOV3 HE4-overexpressing clones.

Conclusions

Overexpression of HE4 promotes collateral resistance to cisplatin and paclitaxel, and downregulation of HE4 partially reverses this chemoresistance. Multiple factors could be involved in HE4-mediated chemoresistance, including deregulation of MAPK signaling, as well as alterations in tubulin levels or stability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-016-0240-0) contains supplementary material, which is available to authorized users.

Regulation of human MAPT gene expression

The number of known pathologies involving deregulated Tau expression/metabolism is increasing. Indeed, in addition to tauopathies, which comprise approximately 30 diseases characterized by neuronal aggregation of hyperphosphorylated Tau in brain neurons, this protein has also been associated with various other pathologies such as cancer, inclusion body myositis, and microdeletion/microduplication syndromes, suggesting its possible function in peripheral tissues. In addition to Tau aggregation, Tau deregulation can occur at the expression and/or splicing levels, as has been clearly demonstrated in some of these pathologies. Here, we aim to review current knowledge regarding the regulation of human MAPT gene expression at the DNA and RNA levels to provide a better understanding of its possible deregulation. Several aspects, including repeated motifs, CpG island/methylation, and haplotypes at the DNA level, as well as the key regions involved in mRNA expression and stability and the splicing patterns of different mRNA isoforms at the RNA level, will be discussed.

Oblongifolin C inhibits metastasis by up-regulating keratin 18 and tubulins

Tumor metastasis is the main cause of cancer-related patient death. In this study, we performed a wound healing migration screen to search for a metastatic inhibitor within our library of natural compounds. We found that oblongifolin C (OC), a natural compound extracted from Garcinia yunnanensis Hu, is an effective inhibitor of metastasis in human esophageal squamous carcinoma Eca109 cells. The transwell migration and matrigel invasion assay results also showed that OC inhibits the migration of Eca109 cells and HepG2 cells. OC can increase the expression of tubulin, indicating that OC inhibits metastasis via tubulin aggregation. In addition, the Western blotting, real-time PCR, and immunostaining results indicated that OC increases the expression of keratin18. Furthermore, the knockdown of keratin 18 by small interfering RNAs inhibited the expression of tubulin and increased the metastasis of cancer cells, suggesting that keratin 18 is the upstream signal of tubulin and plays a vital role in metastasis. A subsequent study in a tail vein injection metastasis model showed that OC can significantly inhibit pulmonary metastasis, as revealed by immunohistochemistry staining. Taken together, our results suggest that OC inhibits metastasis through the induction of the expression of keratin 18 and may be useful in cancer therapy.