Estrogen and antiestrogen-dependent regulation of breast cancer cell proliferation in multicellular spheroids: Influence of cell microenvironment

17-β Estradiol up-regulates energy metabolic pathways, cellular proliferation and tumor invasiveness in ER+ breast cancer spheroids

Several biological processes related to cancer malignancy are regulated by 17-β estradiol (E2) in ER+-breast cancer. To establish the role of E2 on the atypical cancer energy metabolism, a systematic study analyzing transcription factors, proteins, and fluxes associated with energy metabolism was undertaken in multicellular tumor spheroids (MCTS) from human ER+ MCF-7 breast cancer cells. At E2 physiological concentrations (10 and 100 nM for 24 h), both ERα and ERβ receptors, and their protein target pS2, increased by 0.6-3.5 times vs. non-treated MCTS, revealing an activated E2/ER axis. E2 also increased by 30-470% the content of several transcription factors associated to mitochondrial biogenesis and oxidative phosphorylation (OxPhos) (p53, PGC1-α) and glycolytic pathways (HIF1-α, c-MYC). Several OxPhos and glycolytic proteins (36-257%) as well as pathway fluxes (48-156%) significantly increased being OxPhos the principal ATP cellular supplier (>75%). As result of energy metabolism stimulation by E2, cancer cell migration and invasion processes and related proteins (SNAIL, FN, MM-9) contents augmented by 24-189% vs. non-treated MCTS. Celecoxib at 10 nM blocked OxPhos (60%) as well as MCTS growth, cell migration and invasiveness (>40%); whereas the glycolytic inhibitor iodoacetate (0.5 µM) and doxorubicin (70 nM) were innocuous. Our results show for the first time using a more physiological tridimensional cancer model, resembling the initial stages of solid tumors, that anti-mitochondrial therapy may be useful to deter hormone-dependent breast carcinomas.

Hypoxia differentially regulates estrogen receptor alpha in 2D and 3D culture formats

Hypoxia is a common feature in solid tumors. Clinical samples show a positive correlation between the expression of the hypoxia-inducible factor HIF-1α and estrogen receptor alpha (ERα) and a negative correlation between HIF-1α and hormone sensitivity. Results from monolayer cultures are in contention with clinical observations, showing that ER (+) cell lines no longer express ERα under hypoxic conditions (1% O₂). Here, we compared the impact of hypoxia on the ERα signaling pathway for T47D cells in a 2D and 3D culture format. In the 2D format, the cells were cultured as monolayers. In the 3D format, paper-based scaffolds supported cells suspended in a collagen matrix. Using ELISA, Western blot, and immunofluorescence measurements, we show that hypoxia differentially regulates ERα protein levels in a culture environment-dependent manner. In the 2D format, the protein levels are significantly decreased in hypoxia. In the 3D format, the protein levels are maintained in hypoxia. Hypoxia reduced ERα transcriptional activation in both culture formats. These results highlight the importance of considering tissue dimensionality for in vitro studies. They also show that ERα protein levels in hypoxia are not an accurate indicator of ERα transcriptional activity, and confirm that a positive stain for ERα in a clinical sample may not necessarily indicate hormone sensitivity.

SAHA inhibits the growth of colon tumors by decreasing histone deacetylase and the expression of cyclin D1 and survivin

We studied the effects of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor, on colon cancer. The expression of HDACs in colorectal cancer specimens and the effects of SAHA on colon cancer cells and tumors of nude mice were assessed. Treatment with SAHA (3 μm) for 72 h induced downregulation of different subtypes of HDAC proteins and also induced acetylation of histone 3 and histone 4. SAHA significantly inhibited the expression of the oncogenic protein c-myc and also increased the expression of the p53 and Rb proteins. The immunohistochemical staining of HDACs, including HDAC1, HDAC2, HDAC3, and HDAC4, was significantly increased in colorectal adenocarcinoma specimens compared to healthy control tissues. In addition, murine studies showed that 100 mg/kg SAHA administered by intraperitoneal injection significantly induced tumor necrosis and inhibited the growth of colon tumors. Immunohistochemistry of the tumor tissues from nude mice revealed that SAHA inhibited the expression of different subtypes of histone deacetylase, the anti-apoptotic proteins cyclin D1, survivin, and also inhibited cell proliferative as determined by Ki67 expression. SAHA inhibited the growth of colon tumors by decreasing histone deacetylases and the expression of cyclin D1 and survivin in nude mice.

Suberoylanilide hydroxamic acid induces apoptosis and sub-G1 arrest of 320 HSR colon cancer cells

BACKGROUND

Histone deacetylases and histone acetyl transferases covalently modify histone proteins, consequentially altering chromatin architecture and gene expression.

METHODS

The effects of suberoylanilide hydroxamic acid, a HDAC inhibitor, on 320 HSR colon cells were assessed in 320 HSR colon cancer cells.

RESULTS

Concentration and time-dependent inhibition of 320 HSR cell proliferation was observed. Treatment of 320 HSR cells with 5 μM SAHA for 72 h significantly inhibited their growth by 50% as compared to that of the control. Fluorescence-activated cell sorting analysis demonstrated significant inhibition of cell cycle progression (sub-G1 arrest) and induction of apoptosis upon various SAHA concentrations after 48 h. In addition, the anti-apoptosis proteins, survivin and Bcl-xL, were significantly inhibited by SAHA after 72 h of treatment. Immunocytochemistry analysis revealed that SAHA-resistant cells were positive for cyclin A (85%), ki-67 (100%), p53 (100%), survivin (100%), and p21 (90%) expression. Furthermore, a significant increase cyclin A-, Ki-67-, p53-, survivin-, and p21-positive cells were noted in SAHA-resistant tumor cells.

CONCLUSION

Our results demonstrated for the first time in 320 HSR colon adenocarcinoma cells that SAHA might be considered as an adjuvant therapy for colon adenocarcinoma.