Cancer stem cells as targets for DC-based immunotherapy of colorectal cancer.

The therapy of colorectal cancer (CRC) patients is often unsuccessful because of the presence of cancer stem cells (CSCs) resistant to conventional approaches. Dendritic cells (DC)-based protocols are believed to effectively supplement CRC therapy. Our study was aimed to assess how the number and properties of CSCs isolated from tumor tissue of CRC patients will affect the biological characteristics of in vitro modified DCs. Similar procedures were conducted with the using of CRC HCT116 and HT29 cell lines. We found that the detailed configuration of CSC-like markers significantly influenced the maturation and activation of DCs after stimulation with cancer cells lysates or culture supernatants. This basic stimulatory effect was enhanced by LPS that is normally present in CRC CSCs niche. The increased number of CD29+ and CD44+ CSCs presented the opposite impact on treated DCs as showed by many significant correlations. The CD133+ CSCs seemed to impair the functions of DCs. The more CD133+ CSCs in tumor sample the lower number of activated DCs evidenced after stimulation. Moreover, our results showed superiority of the spherical culture model over the adherent one since spherical HCT116 and HT29 cells presented similar influence on DCs properties as CRC patients cancer cells. We concluded that the DCs features may depend directly on the properties of CSCs affected by progression status of tumor.

In vitro characterization of spheres derived from colorectal cancer cell lines.

Spherical cultures (SCs) can be regarded in cancer research as a link between in vitro investigations on cancer lines and in vivo studies of tumor development. SCs are believed to mimic tumor architecture and to be enriched in cancer stem cell-like cells (CSC-like cells). In the present study we characterized colonospheres derived from colorectal cancer (CRC) cell lines, and we confirmed the ability of HCT116 and HT29 cell lines to form spheres within serum-free medium, however, the detailed analysis presented the major differences concerning their characteristics including morphology, phenotype, proliferative potential, distribution in the cell cycle phases and spherogenicity. Moreover, after we magnetically separated CD133+ and CD133- cells we could conduct the analogical analysis as we performed for the original cells. We observed that all cellular fractions unveiled sphere formation capacity, even when cultured in limited number of cells per well and only SCs originated from CD133+ fraction resembled morphologically the parental spheres. Both CD133+ and CD133- subsets derived from HCT116 line were more enriched in cells in G0/G1 phase of the cell cycle in comparison to their HT29 analogues. Additionally, proliferative potential also varied amongst all studied fractions. Surprisingly, 3-D invasion assay revealed that only HCT116-derived populations were able to migrate into extended regions of Matrigel Matrix confirming their higher aggressiveness. Our results provided comprehensive characterization of CRC cell lines culture in adherent and spherical forms and, what seems to be the most advantageous, the comparison of two distinct fractions after magnetic separation. As we found the specific features of cells presented line- and expansion mode-dependency, thus, such complete description might appear crucial before CRC lines would be involved into sophisticated assays, especially focused on potentially novel therapeutic agents targeting CSC-like cells.

Therapeutic strategies against cancer stem cells in human colorectal cancer.

Colorectal cancer (CRC) is the third most frequent malignancy and represents the fourth most common cause of cancer-associated mortalities in the world. Despite many advances in the treatment of CRC, the 5-year survival rate of patients with CRC remains unsatisfactory due to tumor recurrence and metastases. Recently, cancer stem cells (CSCs), have been suggested to be responsible for the initiation and relapse of the disease, and have been identified in CRC. Due to their basic biological features, which include self-renewal and pluripotency, CSCs may be novel therapeutic targets for CRC and other cancer types. Conventional therapeutics only act on proliferating and mature cancer cells, while quiescent CSCs survive and often become resistant to chemotherapy. In this review, markers of CRC-CSCs are evaluated and the recently introduced experimental therapies that specifically target these cells by inducing CSC proliferation, differentiation and sensitization to apoptotic signals via molecules including Dickkopf-1, bone morphogenetic protein 4, Kindlin-1, tankyrases, and p21-activated kinase 1, are discussed. In addition, novel strategies aimed at inhibiting some crucial processes engaged in cancer progression regulated by the Wnt, transforming growth factor ß and Notch signaling pathways (pyrvinium pamoate, silibinin, PRI-724, P17, and P144 peptides) are also evaluated. Although the metabolic alterations in cancer were first described decades ago, it is only recently that the concept of targeting key regulatory molecules of cell metabolism, such as sirtuin 1 (miR-34a) and AMPK (metformin), has emerged. In conclusion, the discovery of CSCs has resulted in the definition of novel therapeutic targets and the development of novel experimental therapies for CRC. However, further investigations are required in order to apply these novel drugs in human CRC.

FasR and FasL in colorectal cancer.

Colorectal cancer (CRC) is one of the most common solid organ cancers prevalent worldwide causing, in spite of advancing therapeutic methodology, high rate of patient mortality, especially due to metastasis development. The cancer stem cell (CSC) theory of tumor growth indicates that CSCs within the tumor mass have great capacity to initiate and sustain tumor growth. Following the suggestion that Fas signaling can be engaged in apoptosis, tumor maintenance, senescence or DICE (death induced by CD95 or CD95L elimination), the attempts to broaden the knowledge concerning the relationships between CSCs features and FasR/FasL appeared to be necessary. The most important advantage of our study was the simultaneously analysis of CSCs from commonly used CRC lines (HCT116 and HT29) and tumor fragments collected from CRC patients. Moreover, the sphere-promoting expansion of CRC lines brought a specific three-dimensional specific environment for CSC exploration. We further investigated the function of Fas signaling in CRC lines depending on the culture mode as we incubated HCT116 and HT29 cells with anti-FasR agonistic antibodies. It appeared to act in a line-dependent and culture mode-dependent manner and influenced some particular features of CSCs such as spherogenicity, proliferation and phenotype. Additionally, the analysis of mRNA level showed that disease progression is associated with significantly increased expression of FasR and/or FasL. In conclusion, our observation seems to confirm that spherical model of cancer lines is more reliable for some sophisticated analysis because of their greater resemblance to the CSCs from human CRC samples in comparison to commonly used adherent cells, at least according to aspects of their biology analyzed in this study. That can be extended to the resemblance of in vitro sphere forming conditions to the in vivo environment. However, the greatest difference concerns the level of apoptosis, thus, this issue require further experiments.

The role of cancer stem cells in pathogenesis of colorectal cancer.

Colorectal cancer (CRC) is the third most commonly diagnosed cancer, accounting for about 10% of total adult malignancies worldwide. The majority of CRC cases are diagnosed at the late stage; thus the investigation of the pathogenesis of early-stage disease and its detection could prevent formation of metastasis, a leading cause of death. This review highlights the recent progress in the understanding of the development of cancer stem cells (CSCs) in the colon epithelium and mechanisms of their proliferation. Moreover, we describe the role of the CSCs in resistance to chemotherapy and formation of metastases. We present evidence for the importance of the interactions between CSCs and their environment in the propagation of the disease. It is hoped that further studies of colorectal cancer CSCs could be helpful in the early detection and improved therapy of this neoplasm.

Decreased expression of RASSF1A tumor suppressor gene is associated with worse prognosis in clear cell renal cell carcinoma.

Clear-cell renal cell carcinoma (ccRCC) is the most common subtype of RCC (70-80%) and is associated with poor prognosis in 40% of cases mainly due to metastasis in the course of the disease. RASSF1, with its isoforms RASSF1A and RASSF1C, is a tumor suppressor gene which has not been fully analyzed in ccRCC yet. The epigenetic downregulation of RASSF1A is commonly associated with promoter hypermethylation. The aim of the present study was to compare the ccRCC outcomes with the expression of RASSF1A and RASSF1C. Tissues were obtained from 86 ccRCC patients. RASSF1A and RASSF1C mRNA levels were assessed in tumor and matched normal kidney tissue, and in 12 samples of local metastases by quantitative PCR (qPCR). RASSF1A and RASSF1C proteins levels were semi-quantified in 58 samples by western blot analysis and their tissue localization was assessed by immunohistochemistry. Hypermethylation of RASSF1A promoter was measured by high-resolution-melting methylation-specific qPCR. RASSF1A mRNA levels were 4 and 5 times lower in 66% of tumor and 75% metastasized samples. RASSF1A hypermethylation was found in 40% of analyzed T cases. RASSF1A protein expression was 5 or 20 times decreased in 70% tumor and 75% metastatic samples, respectively. RASSF1A hypermethylation, mRNA and protein levels were associated with TNM progression and higher Fuhrman's grading. Decreased RASSF1A expression, hypermethylation, TNM and Fuhrman's grading were associated with poorer overall survival (OS). Cox hazard ratio (HR) analysis revealed predictor role of RASSF1A mRNA levels on OS and progression-free survival (PFS) in relation to Fuhrman's grading (OS HR=2.25, PFS HR=2.93). RASSF1C levels were increased in ccRCC; no correlations with clinicopathological variables were found. We conclude that RASSF1C gene is not involved in ccRCC progression and we propose that the measurements of RASSF1A mRNA levels in paired tumor-normal kidney tissue could serve as a new prognostic factor in ccRCC.