Hypoxia inhibition of camptothecin-induced apoptosis by Bax loss

Genotoxic and Anti-Migratory Effects of Camptothecin Combined with Celastrol or Resveratrol in Metastatic and Stem-like Cells of Colon Cancer

Background: Colorectal cancer is one of the leading and most lethal neoplasms. Standard chemotherapy is ineffective, especially in metastatic cancer, and does not target cancer stem cells. A promising approach to improve cancer treatment is the combination therapy of standard cytostatic drugs with natural compounds. Several plant-derived compounds have been proven to possess anticancer properties, including the induction of apoptosis and inhibition of cancer invasion. This study was focused on investigating in vitro the combination of camptothecin (CPT) with celastrol (CEL) or resveratrol (RSV) as a potential strategy to target metastatic (LOVO) and stem-like (LOVO/DX) colon cancer cells. Methods: The genotoxic effects that drive cancer cells into death-inducing pathways and the ability to inhibit the migratory properties of cancer cells were evaluated. The γH2AX+ assay and Fast-Halo Assay (FHA) were used to evaluate genotoxic effects, the annexin-V apoptosis assay to rate the level of apoptosis, and the scratch test to assess antimigratory capacity. Results: The results showed that both combinations CPT-CEL and CPT-RSV improve general genotoxicity of CPT alone on metastatic cells and CSCs. However, the assessment of specific double-stranded breaks (DSBs) indicated a better efficacy of the CPT-CEL combination on LOVO cells and CPT-RSV in LOVO/DX cells. Interestingly, the combinations CPT-CEL and CPT-RSV did not improve the pro-apoptotic effect of CPT alone, with both LOVO and LOVO/DX cells suggesting activation of different cell death mechanisms. Furthermore, it was found that the combinations of CPT-CEL and CPT-RSV improve the inhibitory effect of camptothecin on cell migration. Conclusions: These findings suggest the potential utility of combining camptothecin with celastrol or resveratrol in the treatment of colon cancer, including more aggressive forms of the disease. So far, no studies evaluating the effects of combinations of these compounds have been published in the available medical databases.

S. M, Birudala G, Jamous YF, Alshargi O, Kotha KK, Sudhan HH, Mani RR, Muthumanickam A, Niranjan D, Jain NK, Agrawal A, Jadon AS, Mayasa V, Jha NK, Kolesarova A, Slama P, Roychoudhury S. Reactive oxygen species mediated apoptotic death of colon cancer cells: therapeutic potential of plant derived alkaloids

Colorectal cancer (CRC) is one of the most deaths causing diseases worldwide. Several risk factors including hormones like insulin and insulin like growth factors (e.g., IGF-1) have been considered responsible for growth and progression of colon cancer. Though there is a huge advancement in the available screening as well as treatment techniques for CRC. There is no significant decrease in the mortality of cancer patients. Moreover, the current treatment approaches for CRC are associated with serious challenges like drug resistance and cancer re-growth. Given the severity of the disease, there is an urgent need for novel therapeutic agents with ideal characteristics. Several pieces of evidence suggested that natural products, specifically medicinal plants, and derived phytochemicals may serve as potential sources for novel drug discovery for various diseases including cancer. On the other hand, cancer cells like colon cancer require a high basal level of reactive oxygen species (ROS) to maintain its own cellular functions. However, excess production of intracellular ROS leads to cancer cell death via disturbing cellular redox homeostasis. Therefore, medicinal plants and derived phytocompounds that can enhance the intracellular ROS and induce apoptotic cell death in cancer cells via modulating various molecular targets including IGF-1 could be potential therapeutic agents. Alkaloids form a major class of such phytoconstituents that can play a key role in cancer prevention. Moreover, several preclinical and clinical studies have also evidenced that these compounds show potent anti-colon cancer effects and exhibit negligible toxicity towards the normal cells. Hence, the present evidence-based study aimed to provide an update on various alkaloids that have been reported to induce ROS-mediated apoptosis in colon cancer cells via targeting various cellular components including hormones and growth factors, which play a role in metastasis, angiogenesis, proliferation, and invasion. This study also provides an individual account on each such alkaloid that underwent clinical trials either alone or in combination with other clinical drugs. In addition, various classes of phytochemicals that induce ROS-mediated cell death in different kinds of cancers including colon cancer are discussed.

Physiological oxygen concentration alters glioma cell malignancy and responsiveness to photodynamic therapy in vitro

OBJECTIVES

The partial pressure of oxygen (pO2) in brain tumors ranges from 5 to 15%. Nevertheless, the majority of in vitro experiments with glioblastoma multiforme (GBM) cell lines are carried out under an atmospheric pO2 of 19 to 21%. Recently, 5-aminolevulinic acid (5-ALA), a precursor of protoporphyrin IX (PpIX), has been introduced to neurosurgery to allow for photodynamic diagnosis and photodynamic therapy (PDT) in high-grade gliomas. Here, we investigate whether low pO2 affects GBM cell physiology, PpIX accumulation, or PDT efficacy.

METHODS

GBM cell lines (U-87 MG and U-251 MG) were cultured under atmospheric (pO2  =  19%) and physiological (pO2  =  9%) oxygen concentrations. PpIX accumulation and localization were investigated, and cell survival and cell death were observed following in vitro PDT.

RESULTS

A physiological pO2 of 9% stimulated GBM cell migration, increased hypoxia-inducible factor (HIF)-1 alpha levels, and elevated resistance to camptothecin in U-87 MG cells compared to cultivation at a pO2 of 19%. This oxygen reduction did not alter 5-ALA-induced intracellular PpIX accumulation. However, physiological pO2 changed the responsiveness of U-87 MG but not of U-251 MG cells to in vitro PDT. Around 20% more irradiation light was required to kill U-87 MG cells at physiological pO2, resulting in reduced lactate dehydrogenase (LDH) release (one- to two-fold) and inhibition of caspase 3 activation.

DISCUSSION

Reduction of oxygen concentration from atmospheric to a more physiological level can influence the malignant behavior and survival of GBM cell lines after in vitro PDT. Therefore, precise oxygen concentration control should be considered when designing and performing experiments with GBM cells.