الفهرس 
Review of literatureOnly 14 pages are availabe for public view
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Abstract
Hepatocellular Carcinoma (HCC) is one of the most common
malignancies and the second leading cause of cancer-related deaths in the
world. In Egypt, hepatocellular Carcinoma (HCC) is the first most common
cancer in men and the second most common cancer in women. Cisplatin is a
well-known chemotherapeutic drug. It is one of the most effective
chemotherapeutics and has been commonly used to treat multiple cancers
including cancers of the bladder, head and neck, ovary, liver, brain and lung.
Approximately 50% of cancer patients who received chemotherapy are cured
with a cisplatin including regimen.
Due to drug resistance and significant side effects, the combination of
cisplatin with other cancer treatments has been utilized as promising
therapeutic strategies for several cancer types. Lacking advantage as a
monotherapy, several combination regimens have been studied. Some
medications are in clinical trials for HCC, but no single-drug has been
approved by the medical community.
The present study aimed at assessing the anti-tumor effect of the natural
compound α-solanine in combination with low concentration of cisplatin on
human hepatocellular carcinoma cell line HepG2. Initially we evaluated the
cytotoxic effect of α-solanine and cisplatin on cell viability. Following 48h of
treatment with increasing doses of α-solanine or cisplatin, cell growth was
inhibited in a dose dependent manner. In separate experiments to evaluate the
cytotoxic effect of α-solanine and cisplatin in combination we used two
combination doses of α-solanine and cisplatin. The two combination doses of
α-solanine 8.5 µM, 5.5 µM and cisplatin 3.1 µM showed a significant more
potent growth inhibitory effect than the individual doses. Calculating the combination index (CI) for these two combinations revealed that using αsolanine with cisplatin showed a synergistic effect.
To further elucidate the mechanism through which our suggested
combinative treatment effectively induced growth inhibition, we analyzed the
effect of α-solanine and/or cisplatin on the alteration of the cell cycle phases,
and the results revealed a combination of α-solanine and cisplatin treatment
induced cell death mostly through a G2/M cell cycle arrest acccompaied with
a reduction the percentage of G0/G1 phase cells. Agents that are capable of
enhancing G2/M arrest were reported to be associated with apoptosis
enhancement and induction of DNA damage.
The mode of cell death was evaluated. Although individual treatments
induced a degree of apoptotic cell death, the combinative treatments showed
higher percentages of early and late apoptotic cells in accordance with the
synergistic cytotoxicity resulted from both compounds. The apoptosis
enhancement and significant increase in the fraction of apoptotic cells in the
late stage as a result of our combinative treatment was confirmed by evaluating
the DNA fragmentation which is an indication of late event in apoptosis.
According to our data, the percentage of DNA fragmentation significantly
elevated following combinative treatments comparing to individual ones in
consistent with the previous experiments.
In this study the caspase-dependent mechanism was detected only when
cells were treated with the lower dose of α-solanine either individually or in
combination with cisplatin as can be evaluated from the significant elevation
of the activity of the executioner caspases 3/7. However, in case of the higher
dose of α-solanine (8.5 µM) this was not the case where no significant
elevation observed in the activity of caspases 3/7 in cells treated with this dose of α-solanine either individually or in in combination with cisplatin. However,
this dose of α-solanine (8.5 µM) in combination with cisplatin was able to
elevate the expression of the death receptors DR4 and DR5, suggesting that
the enhanced apoptotic processes detected from this dose of combinative
treatment is independent of caspase 3/7 activity but mediated by release of
death receptors. The shift in the apoptotic mode of cell death from caspase-3
dependent to caspase-3 independent induced by the use of low vs. high drug
dose has been reported before suggesting that for the same drug the
mechanism of induced apoptotic cell death would differ based on the dose
used.
The anti-proliferative effect as a result of apoptosis enhancement that
has been detected using our combinative treatment was also found to be
modulated by a reduction in the proportion of CD133+
cells after treatment
with the low dose of α-solanine (5.5 µM) or cisplatin (3.1 µM) either
individually or in combination. Several studies suggested that suppression of
CD133 could reduce the stemness properties and enhances the
chemosensitivity of cells providing an efficient strategy to target tumor
resistance cells.
Some of the key molecular markers that play crucial role in apoptosis
were evaluated to estimate the involvements of these markers in cell death
induced by our combinative treatment. The expression levels of anti-apoptotic
markers Bcl-2 and survivin were significantly decreased following the
treatment of cells with the combinations α-solanine and cisplatin concomitant
with the significant elevation in the apoptotic pathway that is detected in the
present study. Inhibition of Bcl-2 and survivin is associated with cisplatin
chemosensitivity enhancement and they are attractive target in cancer therapy.n this study, the two used doses of α-solanine were able to significantly
modulate and reduce the expression of miR-21 either used alone or in
combination with cisplatin and this effect is in accordance with the detected
anti-proliferation effect and apoptosis enhancement.
Bcl-2, survivin and miR-21 are reported to cooperate and participate in
tumor progression and the inhibition of miR-21 was able to efficiently
suppress cell proliferation through a modulation in the expression of Bcl-2 and
survivin. Moreover, miR-21 was reported to be strongly participated in
cisplatin resistance and targeting this miRNA could modulate the chemosensitivity of cells toward platinum based agents.