Androgen receptors in rectal and colonic cancer

Delineating the role of nuclear receptors in colorectal cancer, a focused review

Colorectal cancer (CRC) stands as one of the most prevalent form of cancer globally, causing a significant number of deaths, surpassing 0.9 million in the year 2020. According to GLOBOCAN 2020, CRC ranks third in incidence and second in mortality in both males and females. Despite extensive studies over the years, there is still a need to establish novel therapeutic targets to enhance the patients' survival rate in CRC. Nuclear receptors (NRs) are ligand-activated transcription factors (TFs) that regulate numerous essential biological processes such as differentiation, development, physiology, reproduction, and cellular metabolism. Dysregulation and anomalous expression of different NRs has led to multiple alterations, such as impaired signaling cascades, mutations, and epigenetic changes, leading to various diseases, including cancer. It has been observed that differential expression of various NRs might lead to the initiation and progression of CRC, and are correlated with poor survival outcomes in CRC patients. Despite numerous studies on the mechanism and role of NRs in this cancer, it remains of significant scientific interest primarily due to the diverse functions that various NRs exhibit in regulating key hallmarks of this cancer. Thus, modulating the expression of NRs with their agonists and antagonists, based on their expression levels, holds an immense prospect in the diagnosis, prognosis, and therapeutical modalities of CRC. In this review, we primarily focus on the role and mechanism of NRs in the pathogenesis of CRC and emphasized the significance of targeting these NRs using a variety of agents, which may represent a novel and effective strategy for the prevention and treatment of this cancer.

Spatial expression of IKK-alpha is associated with a differential mutational landscape and survival in primary colorectal cancer

BACKGROUND

To understand the relationship between key non-canonical NF-κB kinase IKK-alpha(α), tumour mutational profile and survival in primary colorectal cancer.

METHODS

Immunohistochemical expression of IKKα was assessed in a cohort of 1030 patients who had undergone surgery for colorectal cancer using immunohistochemistry. Mutational tumour profile was examined using a customised gene panel. Immunofluorescence was used to identify the cellular location of punctate IKKα expression.

RESULTS

Two patterns of IKKα expression were observed; firstly, in the tumour cell cytoplasm and secondly as discrete 'punctate' areas in a juxtanuclear position. Although cytoplasmic expression of IKKα was not associated with survival, high 'punctate' IKKα expression was associated with significantly reduced cancer-specific survival on multivariate analysis. High punctate expression of IKKα was associated with mutations in KRAS and PDGFRA. Dual immunofluorescence suggested punctate IKKα expression was co-located with the Golgi apparatus.

CONCLUSIONS

These results suggest the spatial expression of IKKα is a potential biomarker in colorectal cancer. This is associated with a differential mutational profile highlighting possible distinct signalling roles for IKKα in the context of colorectal cancer as well as potential implications for future treatment strategies using IKKα inhibitors.

Somatic alterations of the androgen receptor CAG repeat in human colon cancer delineate a novel mutation pathway independent of microsatellite instability

The human androgen receptor gene contains a polymorphic CAG repeat region ranging from 8 to about 35 repeats in the normal human population. The repeat length is inversely related to the transactivation potential of the receptor. We have analyzed the repeat length in 50 sporadic colon cancer samples in comparison to surrounding healthy mucosa and have found somatic reductions of up to 10 repeats in 5 cases (10%), 3 of which were complex, probably involving both alleles. Alterations occurred in tumors with and without microsatellite instability indicating that they follow an independent mutation pathway. The similar repeat of the huntingtin gene did not show any somatic alterations in the same cases. No correlation to sex, tumor stage, location, or histology was evident. In the tumors that showed somatic reductions, the reduced allele was present in at least half of the cells and thus in most, if not all, of the tumor component of the sample. Somatic reductions of the androgen receptor CAG repeat thus occur frequently, through a pathway distinct from microsatellite instability and early during colon carcinogenesis. The receptor is expressed in most normal and neoplastic tissue samples analyzed. Apparent growth selection of cells bearing shortened AR alleles suggests that androgens contribute to colon carcinogenesis in a yet unknown way.

Cell surface molecules and their prognostic values in assessing colorectal carcinomas

OBJECTIVE

Carcinomas of the colon and rectum are the third leading cause of cancer-related deaths. Although advances in the surgical treatment of primary colorectal cancers have lead to improvements in patient survival at early tumor stages, treatment of more progressive cancers has not resulted in dramatic improvements in patient survival. However, the selection of patient subgroups based on their prognosis and other characteristics could result in improved outcomes from adjuvant therapies in patients with Dukes B and C carcinomas.

METHODS

The authors reviewed the available data on the value of cell surface molecules in assessing the prognosis of colorectal carcinomas, paying specific attention to the evaluation of statistical analysis and multivariate procedures.

RESULTS

Cell surface molecules have been identified on colorectal carcinoma cells whose expression appears to be related to malignant transformation, tumor progression, or patient prognosis. Among these cell surface molecules, various cell adhesion molecules, growth factor receptors, proteinases, and their receptors and inhibitors have been identified as potentially useful prognostic markers.

CONCLUSIONS

Although data exist on the prognostic values of certain cell surface markers, the use of multivariate analysis for the identification of valuable prognostic factors remains uncommon. Using reproducible and standardized multivariate analysis procedures, new tumor markers should be carefully examined for their biologic and prognostic relevance before being considered as potentially useful in the management of colorectal cancers.

Metabolic phenotypes and colorectal neoplasia

It now appears likely that the development of colonic adenomas and carcinomas involves a series of steps in which environmental or endogenous carcinogens induce or promote neoplasia through the accumulation of multiple, specific genetic mutations. Genetic predisposition to this process may take the form of inherited defects in control of cellular proliferation as in familial polyposis coli, or genetically determined polymorphism which affects enzyme activities relevant to the production or detoxication of carcinogens. Genetic effects may also influence levels of hormones and/or their target cell receptors which regulate the metabolic and proliferative activity of colonocytes. This review highlights data suggesting a role for polymorphism associated with xenobiotic acetylation, hydroxylation, and conjugation with glutathione in the metabolism of potential carcinogens, as well as for dehydroepiandrosterone in the metabolic control of cell proliferation. The study of genetically determined polymorphism in colorectal cancer may provide new insights into the epidemiology of cancer and result in new methods for the detection of higher risk groups.

Effect of steroid hormones on human colorectal adenocarcinoma xenografts, of known steroid-receptor status, in nude mice

The effect of hormone therapy on the growth of human colonic adenocarcinoma xenografts in nude mice was evaluated. Primary xeno-transplantation for ten different human colorectal adenocarcinomas into nude mice yielded a tumour take of 50%. One of these host tumours was found to contain androgen receptors (8 fmol/mg cytosol protein; Kd 0.73 x 10(-9) M), which were maintained in the xenograft at the third and ninth passages, but not expressed at the tenth and twelfth passages. The host tumour and its xenograft did not express either oestrogen or progesterone receptors. Administration of dihydrotestosterone led to inhibition of xenograft growth at the ninth passage compared with untreated controls (P less than 0.05), but had no effect on xenograft growth at the tenth and twelfth passages when androgen receptors were absent. Stilboestrol and progesterone failed to influence xenograft growth. In conclusion, dihydrotestosterone administration led to inhibition of xenograft growth only in the presence of androgen receptor, suggesting that some colorectal cancers might be considered steroid-hormone-sensitive tumours.

Androgen receptors in colorectal adenomas

To evaluate the potential effect of androgens on the development and growth of human colorectal adenomas, the prevalence and concentration of cytosolic androgen receptors (AR) were analysed in 26 adenomas and 19 samples of normal colonic mucosa by a hybrid ligand receptor-binding assay. AR were detected in 7 of the adenomas (26.9%), and in 6 of the normal mucosa samples (31.6%). In the adenomas, AR levels demonstrated were low, ranging from 6 to 31 fmol/mg cytosol protein, and dissociation constants (Kds) ranged from 0.17-2.7 X 10(-9) M. Of 13 adenomas excised from men, 6 (46%) had positive receptor activity, whereas only 1 of 13 (7.7%) from women was positive (P = 0.03, Fisher's exact test). There was no correlation between AR titre and patient age, or between adenoma size and histological type or degree of dysplasia. In normal mucosa, AR levels ranged from 7 to 33 fmol/mg and Kds ranges from 0.24-3.1 X 10(-9) M. There was no significant difference between either AR prevalence or levels in the adenomas and normal mucosa. The sex difference was exclusive to the adenoma. Endogenous androgen may play a role in adenoma development early in the promotional process.

[Nutrition and the etiology of colon cancer: from descriptive epidemiology to dietary prevention]

Colon cancer is one of the most frequent forms of cancer in the Federal Republic of Germany and in most Western countries, but is, however, generally rare in Africa, Asia, and Latin America. Based on epidemiological investigations, differing dietary practices are considered to be main reason for these differences. A high fat and protein consumption was identified as a risk factor, while a high fibre content of the diet was found to be protective. Existing hypotheses of the etiology of colon cancer, which are based on the two-stage initiation-promotion model, regard interactions between initiators, promotors, and inhibitors as decisive for the final outcome of colon cancer. Possible initiators are pyrolysis products of protein-rich food (meat or fish), generated by heating, and products of metabolism of intestinal bacteria (e.g. faecal mutagens, N-nitroso compounds, transformation products of bile acids). Fats probably exert their influence only at the promotional stage. The diet-dependent bacterial formation of deoxycholic and lithocholic acids is a possible mechanism which has been experimentally substantiated. The protective effect of a diet rich in fibre seems to be mediated in particular by dilution and adsorption of harmful compounds. Further protective factors in human diet may be calcium, selenium, vitamin A and beta-carotene. In this paper, evidence, both supporting and refuting the existing hypotheses, is discussed, as well as the possibilities of dietary prevention of colon cancer.