Hussein Akil

Hallmarks in colorectal cancer: Angiogenesis and cancer stem-like cells

Carcinogenesis is a multistep process that requires the accumulation of various genetic and epigenetic aberrations to drive the progressive malignant transformation of normal human cells. Two major hallmarks of carcinogenesis that have been described are angiogenesis and the stem cell characteristic of limitless replicative potential. These properties have been targeted over the past decade in the development of therapeutic treatments for colorectal cancer (CRC), one of the most commonly diagnosed and lethal cancers worldwide. The treatment of solid tumor cancers such as CRC has been challenging due to the heterogeneity of the tumor itself and the chemoresistance of the malignant cells. Furthermore, the same microenvironment that maintains the pool of intestinal stem cells that contribute to the continuous renewal of the intestinal epithelia also provides the necessary conditions for proliferative growth of cancer stem-like cells. These cancer stem-like cells are responsible for the resistance to therapy and cancer recurrence, though they represent less than 2.5% of the tumor mass. The stromal environment surrounding the tumor cells, referred to as the tumor niche, also supports angiogenesis, which supplies the oxygen and nutrients needed for tumor development. Anti-angiogenic therapy, such as with bevacizumab, a monoclonal antibody against vascular-endothelial growth factor, significantly prolongs the survival of metastatic CRC patients. However, such treatments are not completely curative, and a large proportion of patient tumors retain chemoresistance or show recurrence. This article reviews the current knowledge regarding the molecular phenotype of CRC cancer cells, as well as discusses the mechanisms contributing to their maintenance. Future personalized therapeutic approaches that are based on the interaction of the carcinogenic hallmarks, namely angiogenic and proliferative attributes, could improve survival and decrease adverse effects induced by unnecessary chemotherapy.

IL22/IL-22R pathway induces cell survival in human glioblastoma cells.

Interleukin-22 (IL-22) is a member of the IL-10 cytokine family that binds to a heterodimeric receptor consisting of IL-22 receptor 1 (IL-22R1) and IL-10R2. IL-22R expression was initially characterized on epithelial cells, and plays an essential role in a number of inflammatory diseases. Recently, a functional receptor was detected on cancer cells such as hepatocarcinoma and lung carcinoma, but its presence was not reported in glioblastoma (GBM). Two GBM cell lines and 10 primary cell lines established from patients undergoing surgery for malignant GBM were used to investigate the expression of IL-22 and IL-22R by using quantitative RT-PCR, western blotting and confocal microscopy studies. The role of IL-22 in proliferation and survival of GBM cell lines was investigated in vitro by BrdU and ELISA cell death assays. We report herein that the two subunits of the IL-22R complex are expressed on human GBM cells. Their activation, depending on exogenous IL-22, induced antiapoptotic effect and cell proliferation. IL-22 treatment of GBM cells resulted in increased levels of phosphorylated Akt, STAT3 signaling protein and its downstream antiapoptotic protein Bcl-xL and decreased level of phosphorylated ERK1/2. In addition, IL-22R subunits were expressed in all the 10 tested primary cell lines established from GBM tumors. Our results showed that IL-22R is expressed on GBM established and primary cell lines. Depending on STAT3, ERK1/2 and PI3K/Akt pathways, IL-22 induced GBM cell survival. These data are consistent with a potential role of IL-22R in tumorigenesis of GBM. Since endogenous IL-22 was not detected in all studied GBM cells, we hypothesize that IL-22R could be activated by immune microenvironmental IL-22 producing cells.

Implications of cleaved caspase 3 and AIF expression in colorectal cancer based on patient age.

A high incidence of colorectal cancer (CRC) has been established in the elderly population. Apoptosis is a key event in maintaining colon homeostasis, both in aging as well as in cancer prevention. Here, we report that colon morphology is affected during the aging process: crypt loss (P=0.045) and increasing distances between crypts (P=0.0001678) were observed, associated with a tendency for mucosa reduction (P=0.083). In addition, our results show that apoptosis plays a determining role on the effect of aging during CRC. Increased expression of cleaved caspase 3 (the key factor implicated in the caspase-dependent pathway; P=0.026 for non-tumor tissues, P=0.0013 for tumor tissues) and AIF (implicated in the caspase-independent pathway; P=0.037) in tissue from elderly patients has been observed. Furthermore, elderly patients respond better to chemotherapy than younger ones (P=9.27 x 10(-5)). These results suggest that patient age should be taken into account to adapt treatment of CRC.

Cancer Stem Cell Niche

Carcinogenesis is a multistep process that requires accumulation of various genetic and epigenetic aberrations that drives the progressive transformation of normal human cells into highly malignant derives. Angiogenesis and limitless replicative potential of cells, the main property of stem cells (SCs), are two major hallmarks of carcinogenesis. In colorectal cancer (CRC), one of the most commonly diagnosed and lethal cancers worldwide, these two steps have been the basis of main therapeutic progresses during the last decade. The cancer stem-like cells (CSC) are a minor population of tumors, representing less than 2.5 % of the tumor mass. They are responsible for the resistance to therapy and the recurrences. In the stromal environment surrounding tumor cells, named tumor niche, CSCs find local and systemic conditions for proliferation.