Selective Growth Inhibition of Carotenoids in Prostate Cancer

Texas Tech University HSC El Paso, Student InternMentor: Dr. Xiaoming GongJoel Quinones

Epidemiology – Prostate Cancer Prostate cancer is the second most common cause

of cancer-related death among men in the USA. In 2015, the National Cancer Institute estimates:

220,800 new cases of prostate cancer 27,540 deaths from prostate cancer

The prostate is a gland which produces a fluid that protects sperm

Figure 1: Prostate cancer statisticsFigure 2: Prostate cancer illustration

Carotenoids and Prostate Cancer Carotenoids are pigments found

in plants, and bacteria. ~700 carotenoids have been

characterized. 25-30 carotenoids are commonly found in human diets.

They have polyisoprenoid structures and are lipophilic.

Dietary carotenoid intake, specifically lycopene, is inversely associated with prostate cancer risk.

Figure 3: Carotenoids structures

Carotenoid Cleavage EnzymesBe

ta-c

arot

ene

15,1

5’-m

onoo

xyge

nase

(BC

O1)

Beta

-car

oten

e 9’

,10’

-dio

xyge

nase

(BC

O2)

Figure 4: Carotenoid Cleavage Pathways

Figure 6: Prostatic Tissue Samples (Western Blot) Cancers BPH Normal Tissues

+BCO2

β-actin

BCO2 Expression in Human Normal and Cancerous Prostate Tissue

Lindqvist et al. J Histochem Cytochem. 2005

Gong et al. PLoS ONE. in press

Figure 5: BCO2 immunohistochemistry – prostatic epithelium (and stroma?)

Hypothesis Carotenoids impair mitochondrial function in cancer cells through

inducing excessive Reactive Oxygen Species (ROS), resulting in cancer cell death.

Mitochondrial BCO2 degrades carotenoids to protect mitochondria from carotenoid-induced dysfunction.

Figure 7: Working model of selective cancer cell killing through carotenoid-induced ROS

Methods: Cell Culture Models Carotenoids: Lutein Lutein epoxide Lycopene Beta-carotene

Cell lines (derived from ATCC): PC-3: Adenocarcinoma, hormone-independent DU 145: Carcinoma, hormone-independent PrEC: Primary prostate epithelial cells

Methods: MTT Assay and Flow Cytometry

MTT Assay: colorimetric assay for cell number Plating cells on a 96-well plate Treating the cells MTT procedure followed by absorbance at 570 nm

Flow Cytometry: cell counting and ROS detection by laser Plate cells in a 6-well plate Treat cells with carotenoids Data are analyzed in a flow cytometer

Figure 8: 96-well culture plate

Lutein inhibits growth of prostate cancer cells but not normal prostatic epithelial cells

Figure 9: MTT assay; conc.-dependent lutein effects on cell growth

P<0.05

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** *

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Lutein Epoxide has inhibitory effect on prostate cancer cells

Figure 10: MTT assay; lutein epoxide effects on prostate cancer cells

P<0.05

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*

*

*

*

*

P<0.05

Lycopene inhibits growth of prostate cancer cells but not normal prostatic epithelial cells

* * *

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Figure 11: MTT assay; conc.-dependent lycopene effects on cell growth

Beta-Carotene has no significant effect on normal or prostate cancer cells

Figure 12: Beta-Carotene effects on Prostate Cell lines

Effects of Lutein ± Chemotherapeutic Agent (Paclitaxel, Px) on Prostate Cancer Cells

Figure 13: Lutein and taxane (Px) effects on PC-3 cells

*

*

*

P<0.05

Effects of Lutein on Intracellular ROS Production in Prostate Cancer Cells

Figure 14: ROS in DU145 and PC-3

Conclusions and Future Directions: Summary:

Lutein and lycopene, but not β-carotene, inhibit prostate cancer cell growth.

There is little apparent reduction in cell viability of PrECs treated with different carotenoids.

Lutein enhances the suppressive effect of a common chemotherapeutic agent, paclitaxel.

Lutein increases intracellular ROS production in prostate cancer DU145 cells

These are the first data to show anticancer effects of lutein, previously recognized principally for its effects in eye and brain health.

Future Directions: Investigate the molecular mechanisms of carotenoid

action in prostate cancer.

Acknowledgments SABR program

Dr. Raj, Jazmine, ValerieDr. Xiaoming GongDr. Lewis P. RubinNorberto PosecionHaley Swanson, Geoffrey Allison,

Christian Draper, Joshua Smith

Questions?