Biologic markers in cancer diagnosis and treatment

Benzene, cytochrome, carcinogenesis: A topic in preventive toxicology

Benzene is a common chemical substance with confirmed toxicity to human beings. The benzene toxicity can be in either acute or chronic. Also, the carcinogenicity of benzene is confirmed. Hence, the control of benzene usage is a topic in preventive toxicology; however, this substance is still problematic in many industrialized settings. In this article, the author discusses benzene and cytochrome focusing on the carcinogenesis process. A further extrapolation on the aspects on preventive toxicology is also included.

The evolution of biomarkers in thyroid cancer-from mass screening to a personalized biosignature

Thyroid cancer is the most common malignancy of the endocrine system. The diagnosis of thyroid nodules, made by neck examination and ultrasonography, is a common event occurring in over 50% of the patient population over the age of 50. Yet, only 5% of these patients will be diagnosed with cancer. Fine needle aspiration biopsy is the gold standard for diagnosing thyroid nodules. However, 10–15% of these biopsies are inconclusive, ultimately requiring a diagnostic thyroid lobectomy. Consequently, research in thyroid biomarkers has become an area of active interest. In the 40 years since calcitonin was first described as the biomarker for medullary thyroid cancer, new biomarkers in thyroid cancer have been discovered. Advances in genomic and proteomic technologies have defined many of these novel thyroid biomarkers. The purpose of this article is to provide a comprehensive literature review of how these biomarkers have evolved from simple screening tests into a complex array of multiple markers to help predict the malignant potential and genetic signature of thyroid neoplasms.

The use of the major anoxic stress response protein P34, the K isozyme of lactate dehydrogenase, and carcinoembryonic antigen in the follow-up of patients with colorectal adenocarcinoma

BACKGROUND

This prospective study evaluated the use of the K isozyme of lactate dehydrogenase (LDH-K) as a complementary tumor marker to carcinoembryonic antigen (CEA) in patients with colorectal adenocarcinoma.

METHODS

In this series, 355 patients underwent potentially curative surgery for primary colorectal adenocarcinoma. A close surveillance program of follow-up revealed 108 patients (30%) who had a serum elevation in CEA and/or LDH-K.

RESULTS

The patients were divided into three groups. Group 1 consisted of 43 patients with elevations in CEA alone. Twenty-seven of 43 patients (63%) had tumor at exploratory laparotomy; and 16 patients (37%) had no evidence of disease after a median follow-up of 74 months. Group 2 consisted of 33 patients with a serum elevation of LDH-K alone. In this group, 5 of 33 patients (15%) had recurrent disease with true elevations of LDH-K. In 28 patients (85%), there were falsely elevated levels of LDH-K with no evidence of disease. Group 3 consisted of 32 patients with elevations of both serum LDH-K and CEA. In this group, 17 of 32 patients (53%) had true elevations of CEA and LDH-K with tumor recurrence, and 15 patients (47%) had false elevations with no evidence of disease.

CONCLUSION

LDH-K did not complement CEA as a tumor marker for detecting recurrence in this group of patients with colorectal cancer.

Carcinoembryonic antigen: function in metastasis by human colorectal carcinoma

Carcinoembryonic antigen (CEA) is a glycoprotein that has been useful as a tumor marker to predict recurrence in gastrointestinal malignancies, but whose biological function has not been elucidated. With the recent evidence that CEA is a member of the immunoglobulin supergene family, CEA may be involved in intercellular recognition and binding. This review examines the role that CEA plays in the development of metastases by colorectal carcinoma.

Predilution hemofiltration for the removal of protein bound antigens

In cancer, tumor antigen (Ag) and the antigen-antibody immune complexes (IC) have been implicated with the inhibition of macrophage or lymphocyte function, interleukin generation and induction of suppressor cells and immunosuppressants. Plasma exchange depletes both Ag and antibodies (Ab) from the circulation. However, the Abs might be cytotoxic to cancer cells. Hence, a better treatment would be to remove the Ag without depleting the Abs. Such a procedure involves dissociation of Ag from Ab either by a change in pH of the plasma or by a hemodilution of the blood followed by removal of both the free and the dissociated Ag by ultrafiltration. The present work presents a theoretical analysis of the predilution hemofiltration system designed to remove the antigens which are weakly bound to proteins. A single pool model for the patient was assumed. The variables which effect the clearance of Ag are the protein binding constant (K), the extent of dilution of blood, the initial ratio between Ag and Ab concentrations. A computer simulation of the derived mass balance equations shows that the clearance of total Ag from the plasma pool decreases with (i) increase in the value of K, but it can be off set by increasing the extent of hemodilution, and (ii) decrease in initial Ag/Ab ratio, but this effect can be minimized by increasing the hemodilution fluid flow rate.

Tumor markers: value and limitations in the management of cancer patients

Sixteen tumor markers are reviewed, and measured to the ideal: produced by the tumor cell alone absent in health and in benign disease present in all patients with a given malignancy level in the blood representative of tumor mass detectable in occult disease. The only marker that approaches the ideal is human chorionic gonadotropin (HCG) in gestational trophoblastic tumors. In this malignancy, the HCG level suggests the diagnosis and stage, confirms response to therapy, and predicts relapse. The three most widely used and intensely studied tumor markers are carcinoembryonic antigen (CEA), alphafetoprotein (AFP), and HCG. CEA cannot be used in screening for cancer, but in carcinoma of the colon its elevation preoperatively increases the likelihood of advanced disease and postoperative recurrence. Postoperatively, elevated titers are often but not invariably associated with recurrent disease. AFP and HCG are useful in the management of nonseminomatous germ cell testicular tumors. Like CEA, they cannot be used for screening. They are more likely to be increased with advancing stage, and after therapy rising levels almost always mean recurrent disease. Some markers are valuable in specific circumstances, such as calcitonin in screening for familial medullary carcinoma of the thyroid. In multiple myeloma, immunoglobulins are useful in determining the tumor mass and response to therapy. In neuroblastoma, catecholamine metabolites are useful primarily in making the diagnosis. In some malignancies, the absence of effective therapy lowers the value of the marker, as for AFP in hepatoma. The remaining markers are too unreliable or too little studied to be useful in the management of an individual patient with cancer. The purpose of this paper is to provide the clinician with an understanding of the limitations of the present tumor markers that will lead to wiser use of the tests, and to provide standards to which future tumor markers should be measured.