Hepatocellular carcinoma in patients with acute intermittent porphyria

Canadian guidance for diagnosis and management of acute hepatic porphyrias

Acute hepatic porphyrias (AHP) comprise four rare monogenic autosomal conditions. Each is linked to a deficiency of heme metabolizing enzymes. Common manifestations include severe abdominal pain, nausea, confusion, hyponatremia, hypertension, tachycardia, and neuropathy. Diagnosis is challenging due to a non-specific, variable presentation with symptoms mimicking other common conditions. Initial diagnosis of AHP can be made with a test for urinary porphobilinogen, δ-aminolevulinic acid and porphyrins using a single random (spot) sample. However, many patients have complications due to delays in diagnosis and management. A novel small interfering RNA-based agent, givosiran, has demonstrated efficacy in reducing acute attacks in a recent Phase III trial, leading to its approval for the management of AHP. Early diagnosis is crucial for the timely introduction of disease-modifying treatments that reduce impairments, enhance quality of life, and extend survival. In this guidance, we aim to improve awareness and outcomes of AHP by making recommendations about diagnosis, monitoring, and treatment in Canada.

Liver transplantation and primary liver cancer in porphyria

The porphyrias are a heterogeneous group of metabolic disorders that result from defects in heme synthesis. The metabolic defects are present in all cells, but symptoms are mainly cutaneous or related to neuropathy. The porphyrias are highly relevant to hepatologists since patients can present with symptoms and complications that require liver transplantation (LT), and some porphyrias are associated with a high risk for primary liver cancer (PLC). Among the cutaneous porphyrias, erythropoietic protoporphyria (EPP) can lead to cholestatic liver failure where LT cures the liver disease but not the porphyria. In acute porphyria (AP), neurotoxic porphyrin precursors are produced in the liver and LT is a curative treatment option in patients with recurrent severe neuropathic attacks. Patients with AP, mainly acute intermittent porphyria, have a significantly increased risk for PLC that warrants surveillance and adequate follow-up of high-risk groups. LT is well established in both EPP with liver failure and AP with recurrent attacks, but most transplant centres have little porphyria experience and cooperation between transplant hepatologists, and porphyria experts is important in the often-difficult decisions on timing and management of comorbid conditions.

Porphyrin precursors and risk of primary liver cancer in acute intermittent porphyria: A case-control study of 188 patients

Acute intermittent porphyria (AIP) is a rare hereditary metabolic disease characterized by acute attacks and accumulation of the porphyrin precursors 5-aminolevulinic acid (ALA) and porphobilinogen (PBG). Patients with AIP have a high risk of primary liver cancer (PLC). We aimed to assess the association between porphyrin precursor excretion and the risk for PLC in patients with AIP. We studied 48 patients with AIP who developed PLC between 1987 and 2015 and 140 age and sex matched controls with AIP but no PLC. Data on all available urinary PBG and ALA samples collected from 1975 until 1 year before PLC diagnosis were analyzed and compared between cases and controls using logistic regression. Porphyrin precursor excretion was higher in patients with PLC (PBG median 7.9 [IQR 4.4-21.9] mmol/mol creatinine) than in controls (3.8 [1.2-9.8]) (adjusted odds ratio 1.07, 95% confidence interval: 1.02-1.12). None of the 28 patients with all registered samples below the upper limit of normal (ULN) developed PLC, and only one of the 45 patients with all samples <2× ULN developed PLC. Among non-PLC controls, ALA and PBG levels decreased after age 50-60 while an increasing trend was observed after age 65 among those who developed PLC. Increased urinary porphyrin precursors are associated with a high risk of developing PLC. Patients with normal levels appear to have a low risk while high or increasing ALA and PBG after age 65 indicates high risk, which should be considered in surveillance decisions.

Comment on Ramai et al. Risk of Hepatocellular Carcinoma in Patients with Porphyria: A Systematic Review. Cancers 2022, 14, 2947

We read with interest this review by Ramai et al. [...].

Risk of Hepatocellular Carcinoma in Patients with Porphyria: A Systematic Review

Simple Summary

Porphyria is a metabolic condition which leads to reduced heme production. While it involves multiple organs systems, porphyria affecting the liver can lead to elevations in hepatic enzymes, progressive fibrosis, cirrhosis and eventually malignancy. Our study looked at the prevalence of liver cancer in patients with porphyria. Overall, we found that patients with porphyria are at increased risk of developing hepatic malignancy. As a result, patients with porphyria should undergo routine surveillance for detecting primary liver malignancy.

Abstract

Acute porphyrias are a group of metabolic disorders resulting in defective porphyrin synthesis and reduced heme production, which carries a risk of malignancy. Porphyrias are inborn defects in the heme biosynthesis pathway resulting in neurovisceral manifestations and cutaneous photosensitivity attacks with multi-systemic involvement. Its estimated prevalence nears 5 per 100,000 patients worldwide. Subclinical liver disease is common, which can progress into transaminitis, fibrosis, cirrhosis, and malignancy. However, data on the incidence of primary liver cancer are lacking. We aim to determine the risk of hepatocellular carcinoma (HCC) in patients with porphyria. A systematic review and pooled analysis were conducted through 2021 on studies assessing blood tests, imaging, cancer development, liver transplant, surgical resection, and outcomes in porphyria. In total, 19 studies, which included 7381 patients with porphyria (3476 females), were considered for the final review. In eight studies, alpha-fetoprotein levels were elevated between 200 and 1000 IU/mL. Of the total cohort of patients with porphyria, primary liver cancer was diagnosed in 351 patients (4.8%), of whom 243 (3.3% of the total) were found to have HCC. A subset of patients was found to have cholangiocarcinoma (n = 18; 0.3% of the total). Interestingly, advanced liver disease or cirrhosis was not a prerequisite for the formation of HCC in a small group of patients. Of the total cohort, 30 patients underwent liver resection, 48 patients underwent liver transplantation, and 327 patients died. Patients with porphyria are at risk of developing primary liver malignancy. Further studies should aim to develop diagnostic and prognostic models aimed at the early detection of HCC in porphyria.

Risk of primary liver cancer in acute hepatic porphyria patients: A matched cohort study of 1244 individuals

BACKGROUND

The acute hepatic porphyrias (AHP) are associated with a risk of primary liver cancer (PLC), but risk estimates are unclear, and what AHP characteristics that predict PLC risk are unknown. In this register-based, matched cohort study, we assessed the PLC risk in relation to biochemical and clinical porphyria severity, genotype, age, and sex.

METHODS

All patients in the Swedish porphyria register with acute intermittent porphyria (AIP), variegate porphyria (VP), or hereditary coproporphyria (HCP) during 1987-2015 were included. This AHP cohort was compared with age-, sex-, and county-matched reference individuals from the general population. National register-based hospital admissions for AHP were used to indicate the clinical severity. For AIP, the most common AHP type, patients were stratified by genotype and urinary porphobilinogen (U-PBG). Incident PLC data were collected from national health registers.

RESULTS

We identified 1244 individuals with AHP (1063 [85%] AIP). During a median follow-up of 19.5 years, we identified 108 incident PLC cases, including 83 AHP patients (6.7%) and 25 of 12,333 reference individuals (0.2%). The adjusted hazard ratio for AHP-PLC was 38.0 (95% confidence interval: 24.3-59.3). Previously elevated U-PBG and hospitalizations for porphyria, but not AIP genotype or sex, were associated with increased PLC risk. Patients aged >50 years with previously elevated U-PBG (n = 157) had an annual PLC incidence of 1.8%.

CONCLUSION

This study confirmed a high PLC risk and identified a strong association with clinical and biochemical AIP activity. Regular PLC surveillance is motivated in patients older than 50 years with a history of active AIP.

Unexpected presentation of acute porphyria

Acute porphyrias are rarely reported in Southeast Asia. They may be underdiagnosed due to their clinical mimicry and lack of awareness among physicians. There is a common cognitive bias to gravitate towards common conditions. In this case report, a 28-year-old woman, who presented with seizures, rhabdomyolysis hyponatraemia and altered mental state, was initially diagnosed as amphetamine overdose. She had presented 3 days prior with abdominal pain, treated for acute cystitis and discharged. On readmission for seizures a day later, she was extensively worked up for altered mental state. Despite normalisation of serum sodium concentration and control of her seizures, she remained unwell. Further investigations later confirmed a diagnosis of acute porphyria. The aim of this case report is to highlight the non-specific nature of presentation of acute porphyria and the importance of considering it as a differential diagnosis in cases of abdominal pain with neuropsychiatric features.

Hepatocellular Carcinoma in Acute Hepatic Porphyrias: Results from the Longitudinal Study of the U.S. Porphyrias Consortium

BACKGROUND AND AIMS

The risk for hepatocellular carcinoma (HCC) is increased in acute hepatic porphyrias (AHP). The aim of this study was to explore the clinicopathologic characteristics, outcomes, and frequency of HCC in patients with AHP in the United States.

APPROACH AND RESULTS

This cross-sectional analysis evaluated patients with HCC in a multicenter, longitudinal study of AHP. Among 327 patients with AHP, 5 (1.5%) were diagnosed with HCC. Of the 5 HCC cases, 4 had acute intermittent porphyria and 1 had variegate porphyria, confirmed by biochemical and/or genetic testing. All patients were white females, with a median age of 27 years (range 21-75) at diagnosis. The median age at HCC diagnosis was 69 years (range 61-74). AHP was asymptomatic in 2 patients; 2 reported sporadic attacks; and 1 reported recurrent attacks (>4 attacks/year). All patients had a single HCC lesion on liver imaging that was 1.8-6.5 centimeters in diameter. Serum alpha fetoprotein levels were below 10 ng/mL in all 4 patients with available results. Four patients underwent liver resection, and 1 was treated with radioembolization. No significant inflammation or fibrosis was found in adjacent liver tissues of 3 patients who underwent liver resection. Two patients developed recurrence of HCC at 22 and 26 months following liver resection. All patients are alive with survival times from HCC diagnosis ranging from 26-153 months.

CONCLUSION

In this U.S. study, 1.5% of patients with AHP had HCC. HCC in AHP occurred in the absence of cirrhosis, which contrasts with other chronic liver diseases. Patients with AHP, regardless of clinical attacks, should be screened for HCC, beginning at age 50. The pathogenesis of hepatocarcinogenesis in AHP is unknown and needs further investigation.

Acute Intermittent Porphyria: An Overview of Therapy Developments and Future Perspectives Focusing on Stabilisation of HMBS and Proteostasis Regulators

Acute intermittent porphyria (AIP) is an autosomal dominant inherited disease with low clinical penetrance, caused by mutations in the hydroxymethylbilane synthase (HMBS) gene, which encodes the third enzyme in the haem biosynthesis pathway. In susceptible HMBS mutation carriers, triggering factors such as hormonal changes and commonly used drugs induce an overproduction and accumulation of toxic haem precursors in the liver. Clinically, this presents as acute attacks characterised by severe abdominal pain and a wide array of neurological and psychiatric symptoms, and, in the long-term setting, the development of primary liver cancer, hypertension and kidney failure. Treatment options are few, and therapies preventing the development of symptomatic disease and long-term complications are non-existent. Here, we provide an overview of the disorder and treatments already in use in clinical practice, in addition to other therapies under development or in the pipeline. We also introduce the pathomechanistic effects of HMBS mutations, and present and discuss emerging therapeutic options based on HMBS stabilisation and the regulation of proteostasis. These are novel mechanistic therapeutic approaches with the potential of prophylactic correction of the disease by totally or partially recovering the enzyme functionality. The present scenario appears promising for upcoming patient-tailored interventions in AIP.

Acute intermittent porphyria: focus on possible mechanisms of acute and chronic manifestations

Porphyrias are a group of inherited metabolic diseases that include eight types, each of which is caused by a mutation that affects an enzyme of the heme biosynthetic pathway. When an enzyme defect has physiological significance, it leads to overproduction of pathway precursors prior to the defective step. The partial absence of the third enzyme in the heme biosynthetic pathway, porphobilinogen deaminase (PBGD) also known as hydroxymethylbilane synthase (HMBS), results in acute intermittent porphyria (AIP), which affects mainly women. Subjects who had AIP symptoms were deemed to have manifest AIP (MAIP). Clinical manifestations are usually diverse and non-specific. Acute AIP episodes may present with abdominal pain, nausea, and vomiting, and repeated episodes may result in a series of chronic injuries. Therefore, studying the mechanisms of acute and chronic manifestations of AIP is of great significance. This review aims to summarize the possible mechanisms of acute and chronic manifestations in patients with AIP.

Hepatocellular carcinoma in acute hepatic porphyrias: A Damocles Sword

Porphyrias are inherited diseases with low penetrance affecting the heme biosynthesis pathway. Acute intermittent porphyria (AIP), variegate porphyria (VP) and hereditary coproporphyria (HCP) together constitute the acute hepatic porphyrias (AHP). These diseases have been identified as risk factors for primary liver cancers (PLC), mainly hepatocellular carcinoma (HCC: range 87-100%) but also cholangiocarcinoma, alone or combination with HCC. In AHP, HCC annual incidence rates range from 0.16 to 0.35% according to the populations studied. Annual incidence rates are higher in Swedish and Norwegian patients, due to a founder effect. It increases above age 50. The pathophysiology could include both direct toxic effects of heme precursors, particularly δ-aminolevulinic acid (ALA), compound heterozygosity for genes implied in heme biosynthesis pathway or the loss of oxidative stress homeostasis due to a relative lack of heme. The high HCC incidence justifies radiological surveillance in AHP patients above age 50. Efforts are made to find new biological non-invasive markers. In this respect, we describe here the first report of PIVKA-II clinical utility in the follow-up of an AIP patient that develop an HCC. In this manuscript we reviewed the epidemiology, the physiopathology, and the screening strategy of HCC in AHP.

The association between chemical-induced porphyria and hepatic cancer

The haem biosynthetic pathway is of fundamental importance for cellular metabolism both for the erythroid and nonerythroid tissues. There are several genetic variants of the pathway in the human population that cause dysfunction of one or other of the enzymes resulting in porphyrias of varying severity. Serious chronic hepatic and systemic diseases may result. Some of these can be precipitated by exposure to drugs including hormones, barbiturates and antibiotics, as well as alcohol and particular chlorinated aromatic chemicals. In experimental animals some of the steps of this pathway can also be severely disrupted by a variety of environmental chemicals, potential drugs and pesticides, especially in the liver, leading to the accumulation of uroporphyrins derived from the intermediate uroporphyrinogens or protoporphyrin IX, the immediate precursor of haem. With some of these chemicals this also leads to cholestasis and liver cell injury and eventually hepatic tumours. The review evaluates the available evidence linking hepatic porphyria with carcinogenesis in naturally occurring human genetic conditions and in chemically-induced porphyrias in laboratory animals. The existing data showing gender, strain, and species differences in sensitivity to the chemical-induced porphyrias, liver injury and liver tumours are discussed and the role that transgenically altered mouse models have played in defining the varying mechanisms. Finally, the review proposes a novel, unifying hypothesis linking the hepatotoxicity induced by the accumulation of various porphyrins, with the increased risk of developing hepatic cancer as a long term consequence.

Acute hepatic porphyria and cancer risk: a nationwide cohort study

BACKGROUND

Acute hepatic porphyria (AHP) is considered to be a risk factor for primary liver cancer (PLC), but varying risk estimates have been published.

OBJECTIVES

Our aim was to investigate the risk of PLC and other cancers in persons with AHP using a nationwide cohort design. Given that greater numbers of women than men tend to have manifest and more severe AHP, a further aim was to investigate sex differences in this risk.

METHODS

The study sample consisted of all Norwegian residents aged 18 years or older during the period 2000-2011. Persons with AHP (n = 251) were identified through the Norwegian Porphyria Centre, and patients with a cancer diagnosis were identified by linkage to the Cancer Registry of Norway.

RESULTS

For persons with AHP, the annual incidence rate of PLC was 0.35%. PLC risk was substantially higher for individuals with an AHP diagnosis compared to the reference population [adjusted hazard ratio (aHR) 108, 95% confidence interval (CI) 56-207]. In a meta-analysis of published studies on PLC and AHP, including ours, women had a higher risk than men. In addition, our results suggested that persons with AHP may have increased risks of kidney (aHR 7.4, 95% CI 2.4-23.1) and endometrial cancers (aHR 6.2, 95% CI 2.0-19.3).

CONCLUSIONS

Our findings confirmed a substantially higher risk of PLC associated with AHP compared to the general population. In a meta-analysis, the risk was shown to be greater for women than men. The novel findings of a moderate to substantial association between AHP and kidney and endometrial cancers should be investigated further.

Genetic, hematological, and immunological disorders transmissible with liver transplantation

It is well recognized that solid organ transplantation can transmit bacterial infection and chronic viral hepatitis as well as certain cancers. As indications for liver transplantation (LT) have expanded, it has been used to treat and even cure certain genetic cholestatic disorders, urea cycle defects, and coagulation abnormalities; many of these conditions are potentially transmissible with LT as well. It is important for clinicians and transplant patients to be aware of these potentially transmissible conditions as unexplained post-LT complications can sometimes be related to donor transmission of disease and thus should prompt a thorough exploration of the donor allograft history. Herein, we will review the reported genetic, metabolic, hematologic, and immunological disorders that are transmissible with LT and describe clinical scenarios in which these cases have occurred, such as in inadvertent or recognized transplantation of a diseased organ, domino transplantation, and with living related liver donation. Liver Transplantation 23 663-678 2017 AASLD.

Update review of the acute porphyrias

Acute porphyrias are rare inherited disorders due to deficiencies of haem synthesis enzymes. To date, all UK cases have been one of the three autosomal dominant forms, although penetrance is low and most gene carriers remain asymptomatic. Clinical presentation is typically with acute neurovisceral attacks characterised by severe abdominal pain, vomiting, tachycardia and hypertension. Severe attacks may be complicated by hyponatraemia, peripheral neuropathy sometimes causing paralysis, seizures and psychiatric features. Attacks are triggered by prescribed drugs, alcohol, hormonal changes, fasting or stress. The diagnosis is made by finding increased porphobilinogen excretion in a light-protected random urine sample. Management includes administration of intravenous human haemin and supportive treatment with non-porphyrinogenic drugs. A few patients develop recurrent attacks, a chronic illness requiring specialist management. Late complications include chronic pain, hepatocellular carcinoma, chronic renal failure and hypertension. In the UK, the National Acute Porphyria Service provides clinical advice and supplies haemin when indicated.

Emerging therapies for acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disease caused by hepatic deficiency of hydroxymethylbilane synthase (HMBS), the third enzyme of the heme synthesis pathway. The dominant clinical feature is acute neurovisceral attack associated with high production of potentially neurotoxic porphyrin precursors due to increased hepatic heme consumption. Current Standard of Care is based on a down-regulation of hepatic heme synthesis using heme therapy. Recurrent hyper-activation of the hepatic heme synthesis pathway affects about 5% of patients and can be associated with neurological and metabolic manifestations and long-term complications including chronic kidney disease and increased risk of hepatocellular carcinoma. Prophylactic heme infusion is an effective strategy in some of these patients, but it induces tolerance and its frequent application may be associated with thromboembolic disease and hepatic siderosis. Orthotopic liver transplantation is the only curative treatment in patients with recurrent acute attacks. Emerging therapies including replacement enzyme therapy or gene therapies (HMBS-gene transfer and ALAS1-gene expression inhibition) are being developed to improve quality of life, reduce the significant morbidity associated with current therapies and prevent late complications such as hepatocellular cancer or kidney failure in HMBS mutation carriers with long-standing high production of noxious heme precursors. Herein, we provide a critical digest of the recent literature on the topic and a summary of recently developed approaches to AIP treatment and their clinical implications.

An update of clinical management of acute intermittent porphyria

Acute intermittent porphyria (AIP) is due to a deficiency of the third enzyme, the hydroxymethylbilane synthase, in heme biosynthesis. It manifests with occasional neuropsychiatric crises associated with overproduction of porphyrin precursors, aminolevulinic acid and porphobilinogen. The clinical criteria of an acute attack include the paroxysmal nature and various combinations of symptoms, such as abdominal pain, autonomic dysfunction, hyponatremia, muscle weakness, or mental symptoms, in the absence of other obvious causes. Intensive abdominal pain without peritoneal signs, acute peripheral neuropathy, and encephalopathy usually with seizures or psychosis are the key symptoms indicating possible acute porphyria. More than fivefold elevation of urinary porphobilinogen excretion together with typical symptoms of an acute attack is sufficient to start a treatment. Currently, the prognosis of the patients with AIP is good, but physicians should be aware of a potentially fatal outcome of the disease. Mutation screening and identification of type of acute porphyria can be done at the quiescent phase of the disease. The management of patients with AIP include following strategies: A, during an acute attack: 1) treatment with heme preparations, if an acute attack is severe or moderate; 2) symptomatic treatment of autonomic dysfunctions, polyneuropathy and encephalopathy; 3) exclusion of precipitating factors; and 4) adequate nutrition and fluid therapy. B, during remission: 1) exclusion of precipitating factors (education of patients and family doctors), 2) information about on-line drug lists, and 3) mutation screening for family members and education about precipitating factors in mutation-positive family members. C, management of patients with recurrent attacks: 1) evaluation of the lifestyle, 2) evaluation of hormonal therapy in women, 3) prophylactic heme therapy, and 4) liver transplantation in patients with severe recurrent attacks. D, follow-up of the AIP patients for long-term complications: chronic hypertension, chronic kidney insufficiency, chronic pain syndrome, and hepatocellular carcinoma.

Metabolic dysregulation in monogenic disorders and cancer - finding method in madness

Cancer is a prime example of a disease process in which carcinogenic and metabolic changes are intertwined to promote cell survival and growth. One approach to unravel this complex relationship is by studying rare, monogenic disorders caused by mutations in genes encoding metabolic enzymes or regulators. There are hundreds of these diseases, most of which manifest in childhood and are collectively termed 'inborn errors of metabolism' (IEMs). Several IEMs demonstrate the consequences of chronic, systemic loss of a particular metabolic activity that can result in malignancy. In this Opinion article, we present a conceptual categorization of IEMs associated with cancer and discuss how assessment of these rare diseases might inform us about the biological foundations of common types of cancer and opportunities for cancer diagnosis and therapy.

Occurrence of Malignant Tumours in the Acute Hepatic Porphyrias

The porphyrias are a group of inherited metabolic diseases resulting from enzymatic deficiencies of specific haem biosynthetic enzymes. They can be classified as primarily acute and non-acute types. Clinically, the acute hepatic porphyrias (AHPs) are characterised by acute neurovisceral attacks. Patients with AHP may be at increased risk for development of hepatocellular carcinoma (HCC). However, systematic studies on the occurrence of other malignancies in patients with the AHPs have not been performed to date. Here, we studied the development of HCC and distinct malignant tumours in patients with the AHPs registered in a single European porphyria specialist centre. A questionnaire was designed and sent to all individuals (n = 122) diagnosed between 1970 and 2012 of whom a valid address was available (n = 82), requesting information on their personal and family history of cancer. Statistical analysis was performed to calculate incidence, prevalence and relative risk of HCC. To calculate confidence intervals, a Poisson distribution was assumed. Forty-nine patients (59.8%) returned a completed questionnaire. Overall, HCC was diagnosed in one female (2.1%), and the remaining patients reported on six distinct malignancies. We were able to confirm that HCC is an important complication in AHP. The patients in our cohort had an approximately 35-fold increased risk of developing HCC, similar to observations in other European countries. In addition, we detected colon, breast, uterine and thyroid cancer as well as lymphoma and a liver metastasis in patients with AHP. However, considering the small number of tumours and patients studied here, the data should be interpreted with caution, and further studies on cancer occurrence in AHP patients will require a multicentre setting.

High risk of primary liver cancer in a cohort of 179 patients with Acute Hepatic Porphyria

BACKGROUND/AIMS

Previous studies have indicated a high risk of hepatocellular carcinoma in acute hepatic porphyrias. In this retrospective study we present the incidence of primary liver cancer and clinical characteristics in a cohort of 179 acute porphyria patients above the age of 50 years.

METHODS

Twenty-three cases with primary liver cancer were found either by a surveillance program or due to clinical suspicion. Standardized rate ratio was used to estimate the relative risk of primary liver cancer after indirect standardization. Survival data were calculated using the Kaplan-Meier method.

RESULTS

The mean age at diagnosis was 69 years. Hepatocellular carcinoma was found in 19 patients while four patients had cholangiocarcinoma or a combination of the two. Four patients had underlying cirrhosis. Mean tumour size was 4.3 cm in the surveillance group and 10.3 cm in the non-surveillance group (p = 0.01). The overall relative risk of primary liver cancer was 86 above the age of 50: 150 for women and 37 for men. Mean survival time was 5.7 years.

CONCLUSION

Acute hepatic porphyria carries a high risk of primary liver cancer above the age of 50 which warrants ultrasound surveillance. Sex distribution and frequency of cirrhosis differs from more common aetiologies of primary liver cancer.

The incidence of inherited porphyrias in Europe

Retrospective estimates of the prevalence of porphyrias have been reported but there has been no large scale prospective study of their incidence. The European Porphyria Network collected information prospectively over a 3 year period about the number of newly diagnosed symptomatic patients with an inherited porphyria (335 patients from 11 countries). Prevalence was calculated from the incidence and mean disease duration. The incidence of hepato-cellular carcinoma (HCC) in acute hepatic porphyria and the prevalence of patients with recurrent acute attacks of porphyria were also investigated. The incidence of symptomatic acute intermittent porphyria (AIP) was similar in all countries (0.13 per million per year; 95 % CI: 0.10 - 0.14) except Sweden (0.51; 95 % CI: 0.28-0.86). The incidence ratio for symptomatic AIP: variegate porphyria: hereditary coproporphyria was 1.00:0.62: 0.15. The prevalence of AIP (5.4 per million; 95 % CI: 4.5-6.3) was about half that previously reported. The prevalence of erythropoietic protoporphyria (EPP) was less uniform between countries and, in some countries, exceeded previous estimates. Fourteen new cases of HCC (11 from Sweden) were reported in patients with acute porphyria. Sixty seven patients (3 VP; 64 AIP: 53 females, 11 males) with recurrent attacks of acute porphyria were identified. The estimated percentage of patients with AIP that will develop recurrent acute attacks was 3-5 %. In conclusion, the prevalence of symptomatic acute porphyria may be decreasing, possibly due to improved management, whereas the prevalence of EPP may be increasing due to improved diagnosis and its greater recognition as a cause of photosensitivity.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-₁ antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-1 antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Review of hepatocellular cancer, hypertension and renal impairment as late complications of acute porphyria and recommendations for patient follow-up

This review critically appraises the data emerging from small retrospective and prospective cohort studies suggesting that patients with the autosomal dominant acute porphyrias may be at increased risk of hepatocellular cancer (HCC), hypertension (HT) and renal impairment. The most striking finding is a marked excess risk of HCC in Swedish patients with acute intermittent porphyria (AIP). As Sweden has a relatively high prevalence of AIP due to a founder effect, it is uncertain to what extent the finding is generalisable to other populations or other acute porphyrias and whether early intervention through screening can improve outcomes. As yet there is no evidence for the cost-effectiveness of systematic surveillance for HCC in acute porphyria outside Sweden. Data from several populations also suggest a high prevalence of chronic sustained HT and renal impairment in AIP, but it is uncertain if this represents a true excess risk, in particular for asymptomatic patients. As these long-term complications are important and potentially treatable, a pragmatic recommendation is that symptomatic patients with acute porphyria should be offered specialist long-term follow-up and, for those aged >50 years, annual liver ultrasound may be considered following discussion of the likely risks and benefits. Opportunistic cardiovascular risk assessment can readily be incorporated into a structured annual review so that appropriate drugs safe for use in acute porphyria are prescribed promptly. As these diseases are rare, collaborative international epidemiological studies such as those being coordinated through the European Porphyria Network are essential to inform best clinical practice.

Insights into the pathogenesis and treatment of cancer from inborn errors of metabolism

Mutations in genes that play fundamental roles in metabolic pathways have been found to also play a role in tumor development and susceptibility to cancer. At the same time, significant progress has been made in the treatment of patients with inborn errors of metabolism (IEM),(1) resulting in increased longevity and the unmasking of cancer predisposition, frequently hepatocellular carcinoma, in these conditions. These patients offer a potential opportunity to deepen our understanding of how intermediary metabolism impacts tumorigenesis. We provide an overview from the perspective of cancers in patients affected with IEM and discuss how dysregulation of these specific metabolic pathways might contribute to the mechanisms of cancer development and treatment.

Screening for hepatocellular carcinoma in acute intermittent porphyria: a 15-year follow-up in northern Sweden

OBJECTIVES

To evaluate the benefit of screening for hepatocellular carcinoma (HCC) in gene carriers of acute intermittent porphyria (AIP) and estimate the annual incidence of HCC in this group.

SUBJECTS

All AIP gene carriers aged ≥55 years from the northernmost county in Sweden, Norrbotten, were invited for screening in this prospective study every 1-1.5 years during the period 1994-2009. We registered all HCC cases amongst AIP gene carriers in the northern region of Sweden (four counties). We compared gene carriers with repeated screening intervals of <2 years (Group A) with controls (Group B; i.e. gene carriers who had never been screened, those screened for the first time or screened at intervals of >2 years, or dropouts). The screening included radiological examination of the liver and relevant laboratory tests.

RESULTS

A total of 62 AIP subjects participated in the study, comprising 33% of the total AIP population aged >55 years in the northern region of Sweden. HCC was diagnosed in 22 AIP subjects (12 men and 10 women), mean age 69 (59-82) years. Amongst these subjects, 73% had experienced prior AIP attacks. The incidence rate ratio for HCC was 64 (52 in men and 93 in women). There were no cases of hepatitis B/C or alcohol abuse. Liver cirrhosis was rare. Liver resection could be performed in most subjects in Group A. Fourteen patients died of HCC, one in Group A and 13 in Group B. Compared with those who were not screened regularly, screening was associated with improved 3-year and 5-year survival (P = 0.005 and 0.038).

CONCLUSIONS

Screening for HCC in carriers of AIP enables early diagnosis and a choice of potentially curative treatments with improved prognosis. We recommend annual screening using liver imaging for AIP gene carriers >50 years of age.

Insights into the pathogenesis and treatment of cancer from inborn errors of metabolism

Mutations in genes that play fundamental roles in metabolic pathways have been found to also play a role in tumor development and susceptibility to cancer. At the same time, significant progress has been made in the treatment of patients with inborn errors of metabolism (IEM),(1) resulting in increased longevity and the unmasking of cancer predisposition, frequently hepatocellular carcinoma, in these conditions. These patients offer a potential opportunity to deepen our understanding of how intermediary metabolism impacts tumorigenesis. We provide an overview from the perspective of cancers in patients affected with IEM and discuss how dysregulation of these specific metabolic pathways might contribute to the mechanisms of cancer development and treatment.

The acute hepatic porphyrias: current status and future challenges

The porphyrias are predominantly inherited metabolic disorders, which result from a specific deficiency of one of the eight enzymes along the pathway of haem biosynthesis. Historically, they have been classified into hepatic and erythropoietic forms, based on the primary site of expression of the prevailing dysfunctional enzyme. From a clinical point of view, however, it is more convenient to subdivide them into acute and non-acute porphyrias, thereby primarily considering the potential occurrence of life-threatening acute neurovisceral attacks. Unrecognised or untreated, such an acute porphyric attack is associated with a significant mortality of up to 10%. The acute hepatic porphyrias comprise acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase deficiency porphyria. Making a precise diagnosis may be difficult because the different types of porphyrias may show overlapping clinical and biochemical characteristics. To date, the therapeutic possibilities are limited and mainly symptomatic. In this overview we report on what is currently known about pathogenesis, clinic, diagnostics, and therapy of the acute hepatic porphyrias. We further point out actual and future challenges in the management of these diseases.

Clinical aspects of acute intermittent porphyria in northern Sweden: a population-based study

The objective of this study was to update the clinical issues of acute intermittent porphyria (AIP), as they have not been in focus for years, and to be aware of potentially associated disorders and social consequences. A total of 356 gene carriers of AIP from northern Sweden participated in this retrospective population-based study. Eight mutations were found with a predominance of W198X (89%). Clinical manifestations of AIP (manifest AIP) were identified in 42%, 65% were women. Women were more severely stricken by AIP attacks concerning number and duration, hospital admission and early onset. Men reporting most attacks were > 40 years of age. In addition to traditional symptoms during attacks, fatigue was commonly described. Chronic AIP symptoms and disability pension due to AIP were reported in about 20% of subjects. Precipitating factors were reported with evident sex differences. Half of the gene carriers who were on medications used drugs considered not safe (in 1999), mainly antihypertensive drugs. Smoking was associated with high AIP attack frequency. Elevated levels of ALT, bile acids, creatinine, U-ALA and U-PBG and decreased levels of creatinine clearance were associated with manifest AIP. The same was true for hypertension and myalgia in the legs. Hepatoma was strikingly overrepresented. The high prevalence of manifest AIP in this study could be explained by a mutation-dependent penetrance. Our results emphasize the importance of early diagnosis, counselling and treatment of attacks, screening and treatment of associated disorders.

The dual face of endogenous alpha-aminoketones: pro-oxidizing metabolic weapons

Amino metabolites with potential prooxidant properties, particularly alpha-aminocarbonyls, are the focus of this review. Among them we emphasize 5-aminolevulinic acid (a heme precursor formed from succinyl-CoA and glycine), aminoacetone (a threonine and glycine metabolite), and hexosamines and hexosimines, formed by Schiff condensation of hexoses with basic amino acid residues of proteins. All these metabolites were shown, in vitro, to undergo enolization and subsequent aerobic oxidation, yielding oxyradicals and highly cyto- and genotoxic alpha-oxoaldehydes. Their metabolic roles in health and disease are examined here and compared in humans and experimental animals, including rats, quail, and octopus. In the past two decades, we have concentrated on two endogenous alpha-aminoketones: (i) 5-aminolevulinic acid (ALA), accumulated in acquired (e.g., lead poisoning) and inborn (e.g., intermittent acute porphyria) porphyric disorders, and (ii) aminoacetone (AA), putatively overproduced in diabetes mellitus and cri-du-chat syndrome. ALA and AA have been implicated as contributing sources of oxyradicals and oxidative stress in these diseases. The end product of ALA oxidation, 4,5-dioxovaleric acid (DOVA), is able to alkylate DNA guanine moieties, promote protein cross-linking, and damage GABAergic receptors of rat brain synaptosome preparations. In turn, methylglyoxal (MG), the end product of AA oxidation, is also highly cytotoxic and able to release iron from ferritin and copper from ceruloplasmin, and to aggregate proteins. This review covers chemical and biochemical aspects of these alpha-aminoketones and their putative roles in the oxidative stress associated with porphyrias, tyrosinosis, diabetes, and cri-du-chat. In addition, we comment briefly on a side prooxidant behaviour of hexosamines, that are known to constitute building blocks of several glycoproteins and to be involved in Schiff base-mediated enzymatic reactions.

Inhibition of 5-aminolevulinic acid-induced DNA damage by melatonin, N1-acetyl-N2-formyl-5-methoxykynuramine, quercetin or resveratrol

Porphyrias are defined as either inborn or acquired diseases related to enzymatic deficiencies in the heme biosynthetic pathway. Lead poisoning, hereditary tyrosinemia, and acute intermittent porphyria (AIP) are characterized by the absence of photosensitivity and the accumulation of 5-aminolevulinic acid (ALA) together with its increased urinary excretion. The main clinical manifestations of AIP are intermittent attacks of abdominal pain, neuromuscular weaknesses and neuropsychiatry alterations, and also an association with primary liver cancer, in which may be involved the oxidative potential of ALA which is able to cause DNA damage. The use of antioxidants in the treatment of ALA-induced oxidative stress is not well established. In the current work, we show the antioxidant efficacy of several compounds including melatonin, quercetin, resveratrol and N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), a melatonin oxidation product, in terms of their ability to limit DNA damage induced by ALA/Fe2+ in an in vitro system. Damage was measured by plasmid DNA strand breaks and detection of 8-oxo, 7-8-dihydro,2'-deoxyguanosine (8-oxodGuo) by high-performance liquid chromatography coupled with electrochemical detection. All compounds tested showed a dose-dependent protective action against free radical damage. These results could be the first step toward studies of the possible use of these antioxidants in oxidative stress promoted by ALA or other pro-oxidants.

Mitochondrial and nuclear DNA damage induced by 5-aminolevulinic acid

5-Aminolevulinic acid (ALA) is a heme precursor accumulated in plasma and in organs in acute intermittent porphyria (AIP), a disease associated with neuromuscular dysfunction and increased incidence of hepatocellular carcinoma (HCC). Liver biopsies of AIP patients showed odd-shaped mitochondria and autophagic vacuoles containing well-preserved mitochondria. ALA yields reactive oxygen species upon metal-catalyzed oxidation and causes in vivo and in vitro impairment of rat liver mitochondria and DNA damage. Using a quantitative polymerase chain reaction assay, we demonstrated that ALA induces a dose-dependent damage in nuclear and mitochondrial DNA in human SVNF fibroblasts and rat PC12 cells. CHO cells treated with ALA also show nuclear DNA damage and human HepG2 cells entered in apoptosis and necrosis induced by ALA and its dimerization product, DHPY. The present data provide additional information on the genotoxicity of ALA, reinforcing the hypothesis that it may be involved in the development of HCC in AIP patients.

Oxidative damage to ferritin by 5-aminolevulinic acid

5-Aminolevulinic acid (ALA), a heme precursor overproduced in various porphyric disorders, has been implicated in iron-mediated oxidative damage to biomolecules and cell structures. From previous observations of ferritin iron release by ALA, we investigated the ability of ALA to cause oxidative damage to ferritin apoprotein. Incubation of horse spleen ferritin (HoSF) with ALA caused alterations in the ferritin circular dichroism spectrum (loss of a alpha-helix content) and altered electrophoretic behavior. Incubation of human liver, spleen, and heart ferritins with ALA substantially decreased antibody recognition (51, 60, and 28% for liver, spleen, and heart, respectively). Incubation of apoferritin with 1-10mM ALA produced dose-dependent decreases in tryptophan fluorescence (11-35% after 5h), and a partial depletion of protein thiols (18% after 24h) despite substantial removal of catalytic iron. The loss of tryptophan fluorescence was inhibited 35% by 50mM mannitol, suggesting participation of hydroxyl radicals. The damage to apoferritin had no effect on ferroxidase activity, but produced a 61% decrease in iron uptake ability. The results suggest a local autocatalytic interaction among ALA, ferritin, and oxygen, catalyzed by endogenous iron and phosphate, that causes site-specific damage to the ferritin protein and impaired iron sequestration. These data together with previous findings that ALA overload causes iron mobilization in brain and liver of rats may help explain organ-specific toxicities and carcinogenicity of ALA in experimental animals and patients with porphyria.

Delta-aminolevulinic acid cytotoxic effects on human hepatocarcinoma cell lines

BACKGROUND

Acute Intermittent Porphyria is a genetic disorder of heme metabolism, characterized by increased levels of porphyrin precursors, delta-aminolevulinic acid (ALA) and porphobilinogen (PBG). ALA has been reported to generate reactive oxygen species and to cause oxidative damage to proteins, subcellular structures and DNA. It is known that oxidative stress can induce apoptosis. The aim of this work was to study the cytotoxic effect of ALA on two hepatocarcinoma cell lines.

RESULTS

We have determined the impact of ALA on HEP G2 and HEP 3B hepatocarcinoma cell lines survival as measured by the MTT assay. ALA proved to be cytotoxic in both cell lines however; HEP G2 was more sensitive to ALA than HEP 3B. Addition of hemin or glucose diminished ALA cytotoxicity in HEP G2 cells; instead it was enhanced in HEP 3B cells. Because apoptosis is usually associated with DNA fragmentation, the DNA of ALA treated and untreated cells were analyzed. The characteristic pattern of DNA fragmentation ladders was observed in ALA treated cells. To elucidate the mechanisms of ALA induced apoptosis, we examined its effect on p53 expression. No changes in p53 mRNA levels were observed after exposure of both cell lines to ALA for 24 h. CDK2 and CDK4 protein levels were reduced after ALA treatment at physiological concentrations.

Genotoxicity of 5-aminolevulinic and 4,5-dioxovaleric acids in the salmonella/microsuspension mutagenicity assay and SOS chromotest

5-Aminolevulinic acid (ALA) is a heme precursor that accumulates in some porphyric disorders and in lead poisoning which can undergo metal-catalyzed oxidation producing reactive oxygen species and the keto-aldehyde, 4,5-dioxovaleric acid (DOVA). Evidence in vitro of ALA-induced DNA lesions suggests that ALA and DOVA have mutagenic potential that could possibly contribute to an increased frequency of hepatocellular carcinoma (HCC) in patients with acute intermittent porphyria (AIP). In this study, we evaluated the genotoxic potential of ALA and DOVA. In the absence of exogenous metabolic activation, ALA and DOVA were mutagenic in Salmonella typhimurium tester strain TA104. ALA was also mutagenic in S. typhimurium TA102, but not in TA98, TA100, or TA1535, indicating an oxidative mechanism. Removal of H(2)O(2) with catalase gave only partial protection, suggesting generation of other mutagenic species. Both ALA and DOVA damaged the DNA of Escherichia coli PQ37, inducing the SOS response detected by an increase in beta-galactosidase activity. These results verified the potential mutagenic activity of ALA and DOVA and reinforce the hypothesis that DNA damage induced by ALA may be associated with the development of HCC in individuals suffering from AIP.

DNA damage by 3,6-dihydropyrazine-2,5-dipropanoic acid, the cyclic dimerization product of 5-aminolevulinic acid

5-Aminolevulinic acid (ALA) is a heme precursor that accumulates in lead poisoning and inborn porphyrias. It has been shown to produce reactive oxygen species upon metal-catalyzed aerobic oxidation and to cause oxidative damage to proteins, liposomes, DNA, and subcellular structures. Studies have also shown that ALA may condense to yield the cyclic product 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY). Here we propose that DHPY could be involved in DNA damage in the presence of high concentrations of ALA. Exposure of plasmid pUC19 DNA to low concentrations of DHPY (2-10 microM) in the presence of 0.1 mM Cu2+ ions causes DNA strand breaks, as demonstrated by agarose gel electrophoresis. It was also shown that in the presence of Cu2+ ions DHPY is able to increase the oxidation of monomeric 2'-deoxyguanosine to form 8-oxo-7,8-dihydro-2'-deoxyguanosine as inferred from high performance liquid chromatography measurements using electrochemical detection. Addition of a metal chelator (bathocuproine, 0.5 mM), the DNA compacting polyamines spermidine (1 mM) and spermine (1 mM) or antioxidant enzymes such as superoxide dismutase (10 microg/ml) and catalase (20 pg/ml) protect the DNA against these damages. The data presented here are discussed with respect to the increased frequency of liver cancer in patients with acute intermittent porphyria.

Melatonin prevents delta-aminolevulinic acid-induced oxidative DNA damage in the presence of Fe2+

Delta-aminolevulinic acid (ALA), a heme precursor which accumulates during lead poisoning and acute intermittent porphyria, is reported to cause liver cancer. The carcinogenic mechanisms of ALA may relate to its ability to generate free radicals through metal-catalyzed oxidation which cause oxidative DNA damage. The aim of this study was to compare the efficacy of melatonin, trolox (vitamin E) and mannitol in altering DNA damage induced by ALA. Herein, we found, in the presence of Fe2+, that ALA-induced formation of 8-hydroxydeoxyguanosine in calf thymus DNA was dose and time-dependent. Melatonin, mannitol and trolox, all of which are free radical scavengers, inhibited the formation of 8-hydroxydeoxyguanosine in a concentration-dependent manner. The concentration of each (melatonin, mannitol and trolox) required to reduce DNA damage by 50%, i.e., the IC50, was 0.52, 0.84 and 0.90 mM, respectively.

Hepatocellular carcinoma in patients with acute hepatic porphyria: frequency of occurrence and related factors

BACKGROUND/AIMS

Previous retrospective studies have suggested an association between hepatocellular carcinoma and acute hepatic porphyrias. The incidence, the relative risk, the characteristics and the outcome of primary liver cancer were prospectively evaluated in patients with acute hepatic porphyrias; the molecular mechanism of carcinogenesis in these patients was also pointed out.

METHODS

A cohort of 650 patients with acute hepatic porphyria was followed over 7 years. Standardized rate ratio was used to measure the relative risk of primary liver cancer after indirect standardization. Morphological and clinical aspects of primary liver cancer were investigated, and survival rates were calculated using the Kaplan-Meier method. Common etiological factors involved in liver carcinogenesis were screened. Excretion rates of porphyrin precursors, serum melatonin levels and mutations in the genes encoding for heme biosynthetic enzymes were studied.

RESULTS

Hepatocellular carcinoma was found in four symptomatic and three asymptomatic patients (four female, three male). The overall standardized rate ratio was 36 (95% CI: 14-74). The 5-year disease-free survival was 43% in patients with hepatocellular carcinoma. Usual risk factors for primary liver cancer were not confounding factors. Hepatocellular carcinoma was not related to specific heme biosynthesis gene mutations. Heme precursors were significantly increased in porphyric patients with hepatocellular carcinoma, and serum melatonin levels were low.

CONCLUSIONS

Acute hepatic porphyrias are risk factors for hepatocellular carcinoma. Hepatic porphyrias should be sought in patients with hepatocellular cancer without obvious etiology, and a periodic screening for hepatocellular carcinoma should be evaluated in these patients. Genes encoding for heme biosynthetic pathway may not act as tumor suppressor genes. Chronic increased levels of delta aminolevulinic acid could lead to the generation of free radicals and subsequently to hepatic carcinogenesis.

Iron mobilization by succinylacetone methyl ester in rats. A model study for hereditary tyrosinemia and porphyrias characterized by 5-aminolevulinic acid overload

Accumulation of 5-aminolevulinic acid (ALA) is an event characteristic of porphyrias that may contribute to their pathological manifestations. To investigate effects of ALA independent of porphyrin accumulation we treated rats with the methyl ester of succinylacetone, an inhibitor of 5-aminolevulinic acid dehydratase that accumulates in the porphyric-like syndrome hereditary tyrosinemia. Acute 2-day treatment of fasted rats with succinylacetone methyl ester (SAME) promoted a 27% increase in plasma ALA. This increase in plasma ALA was accompanied by augmentation of the level of total nonheme iron in liver (37%) and brain (20%). Mobilization of iron was also indicated by 49% increase in plasma iron and a 77% increase in plasma transferrin saturation. Liver responded with a mild (12%) increase in ferritin. Under these acute conditions, some indications of oxidative stress were evident: a 15% increase in liver reactive protein carbonyls, and a 42% increase in brain subcellular membrane TBARS. Brain also showed a 44% increase in CuZnSOD activity, consistent with observations in treatment with ALA. Overall, the data indicate that SAME promotes ALA-driven changes in iron metabolism that could lead to increased production of free radicals. The findings support other evidence that accumulation of ALA in porphyrias and hereditary tyrosinemia may induce iron-dependent biological damage that contributes to neuropathy and hepatoma.

Genotoxic potential of porphyrin type photosensitizers with particular emphasis on 5-aminolevulinic acid: implications for clinical photodynamic therapy

Photodynamic therapy (PDT) uses exogenously administered photosensitizers activated by light to induce cell death or modulation of immunological cascades, presumably via formation of reactive oxygen species (ROS). 5-Aminolevulinic acid (ALA) mediated photosensitization is increasingly used for the treatment of nonmelanoma skin cancer and other indications including benign skin disorders. Long-term side effects of this investigational modality are presently unknown. Just as tumor treatments such as ionizing radiation and chemotherapy can cause secondary tumor induction, PDT may potentially have a carcinogenic risk. Evaluation of the biological effects of ALA in absence of activating light and analysis of the mechanism of ALA-PDT and porphyrin-type photosensitizers mediated photosensitization indicate that this therapy has a pro-oxidant and genotoxic potential. However, porphyrin type molecules also possess antioxidant and antimutagenic properties. ALA-PDT delays photocarcinogenesis in mice, and topical ALA alone does not increase skin cancer incidence in these animals. Patients with increased tissue levels of ALA have an increased incidence of internal carcinoma, however, it is not clear whether this relationship is casual or causal. There is no evidence indicating higher rates of skin cancer in patients with photosensitivity diseases due to presence of high protoporphyrin IX (PP) levels in skin. Overall, the presently available data indicate that the risk for secondary skin carcinoma after topical ALA-PDT seems to be low, but further studies must be carried out to evaluate the carcinogenic risk of ALA-PDT in conditions predisposed to skin cancer.