Browse Subject Areas

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Physical Activity and Natural Anti-VIP Antibodies: Potential Role in Breast and Prostate Cancer Therapy

Physical Activity and Natural Anti-VIP Antibodies: Potential Role in Breast and Prostate Cancer Therapy

  • Milena Veljkovic, 
  • Violeta Dopsaj, 
  • Milivoj Dopsaj, 
  • Donald R. Branch, 
  • Nevena Veljkovic, 
  • Maria M. Sakarellos-Daitsiotis, 
  • Veljko Veljkovic, 
  • Sanja Glisic, 
  • Alfonso Colombatti



There is convincing evidence from numerous clinical and epidemiological studies that physical activity can reduce the risk for breast and prostate cancer. The biological mechanisms underlying this phenomenon remain elusive. Herein we suggest a role for naturally produced antibodies reactive with the vasoactive intestinal peptide (VIP) in the suppression of breast and prostate cancer, which we believe could offer a possible molecular mechanism underlying control of these cancers by physical exercise.

Methodology and Results

We found that sera from individuals having breast and prostate cancers have decreased titers of VIP natural antibodies as demonstrated by a lower reactivity against peptide NTM1, having similar informational and structural properties as VIP. In contrast, sera collected from elite athletes, exhibited titers of natural NTM1-reactive antibodies that are significantly increased, suggesting that physical activity boosts production of these antibodies.


Presented results suggest that physical exercise stimulates production of natural anti-VIP antibodies and likely results in suppression of VIP. This, in turn, may play a protective role against breast and prostate cancers. Physical exercise should be further investigated as a potential tool in the treatment of these diseases.


The vasoactive intestinal peptide (VIP) is a pleiotropic peptide important in many physiologic functions, including glucose homeostasis, neuroprotection, memory, gut function, modulation of the immune system and circadian function. In addition, there are numerous evidences that (VIP) and its receptors, which are highly expressed in breast tumor cells [1],[2],[3],[4],[5],[6],[7],[8], play an important role in the pathogenesis of breast cancer. VIP functions as an autocrine growth factor [8],[9] and regulates proliferation, survival, and differentiation in human breast cancer cells [10]; it has proangiogenic functions [11] in breast cancer. VIP also induces transactivation of epidermal growth factor receptor (EGFR) and human epidermal growth factor-2 receptor (HER2) and increases expression of c-fos, c-jun and c-myc oncogenes [2],[12],[13]. There also is mounting evidence that VIP is involved in the pathogenesis of prostate cancer. VIP increases the expression of the major angiogenic factor VEGF [14] and acts as a proangiogenic factor [15],[16],[17]. VIP increases neuroendocrine differentiation [18] and stimulates interleukin-6 production [19] and prostate-specific antigen (PSA) secretion in prostate cancer [20]. In addition, VIP stimulates HER2 transphosphorylation in androgen-independent prostate cancer cells [17], stimulates their invasive capacity [21] and contributes to prostate cancer pathogenesis by induction of malignant transformation [22]. VIP antagonists suppress the release of prostate-specific antigen (PSA) [23] and inhibit growth of breast and prostate cancer cells [24],[25],[26],[27],[28],[29].

Taken together, these observations strongly support the notion that VIP plays an important role in breast and prostate cancer pathogenesis and suggests that elevated concentrations of VIP in the circulation may represent a risk factor for these cancer types.

VIP is elevated in plasma after aerobic exercise [30],31[31],[32],[33],[34],[35],[36] suggesting that physical activity represents a potential stimulus for VIP autoantibody formation [37],[38]. Because of the immunomodulatory and neuromodulatory activities of VIP, circulating levels of this peptide are under tight control and natural anti VIP autoantibodies are potent modifiers of its biological actions and important regulators of its circulating level [39],[40],[41],[42],[43]. However, the antigenic stimulus leading to the formation of these autoantibodies has not been identified yet. It was previously shown that structural and informational similarity, represented by the informational spectrum frequencies, is essential for the immunological cross-reactivity between VIP and HIV-1 gp120 [44],[45],[46],[47]. This analysis revealed that peptide FTDNAKTI (NTM1) represented the shortest gp120-derived peptide resembling informational and structural properties of VIP [48].

The present study was carried out in order to compare reactivity with peptide NTM1 of sera collected from individuals with breast and prostate cancer and sera from elite athletes. Obtained results showed a significant difference in NTM1 reactivity of sera from elite athletes, healthy controls and cancer patients.


Reactivity of sera collected from subjects with breast and prostate cancer with peptide (NTM1s)4-SOC4 was determined by the ELISA immunoassay (Figure 1 and Table 1). Statistical analysis revealed that this reactivity in sera from cancer patients was significantly lower in comparison with the reactivity of control sera P(0.02) and P(3.7e-05) in breast and prostate cancer, respectively). In Table 2 is given the total IgG content determined for breast and prostate cancer patients.

Figure 1. Results of ELISA.

The absorbance values (OD) obtained for sera of cancer patients, athletes and healthy control subjects with peptide NTM1. Antibodies recognizing peptide NTM1 are significantly more prevalent in serum samples from athletes compared to control subjects (swimming P(2.9e-06), water polo P(0.0001), volleyball P(8.1e-07), rowing P(1.8e-06), wrestling P(0.0009), and karate P(3.2e-07); Mann-Whitney test). The absorbance values for sera from cancer patients are significantly lower in comparison with the values obtained for control sera (P(0.02) and P(3.7e-05) in breast and prostate cancer, respectively; Mann-Whitney test).

Table 1. Comparison of the reactivity with peptide NTM1 of sera from cancer patients, athletes and healthy control subjects.

Table 2. Data for investigated breast and prostate cancer patients and the absorbance values obtained for their sera with peptide NTM1.

In Figure 1 and Table 1 are presented the results of ELISA testing of sera collected from elite athletes. Analysis showed that (NTM1s)4-SOC4-reactivity of sera from elite athletes was highly significantly different (i) from reactivity of sera collected from healthy, sedentary controls (for female: swimming P(2.9e-06), water polo P(0.0001), volleyball P(8.1e-07), all female elite athletes P(2e-6); for male: rowing P(1.8e-06), wrestling P(0.0009), karate P(3.2e-07), all male elite athletes P(2e-6)), and (ii) from sera from cancer patients (for breast cancer: swimming P(1.2e-05), water polo P(4.1e-6), volleyball P(7.1e-06), all female elite athletes P(2e-6); for prostate cancer: rowing P(1.8e-06), wrestling P(1.2e-5), karate P(6.4e-07), all female elite athletes (2e-9).


There is now strong and consistent evidence from several studies conducted worldwide that regular physical activity reduces breast cancer risk by 20% to 30% and that a dose–response effect exists [49]. Long-term athletic training during the college and pre-college years lowers the risk of breast cancer throughout the life span [50],[51],[52]. For tertiary cancer prevention, observational studies suggest that breast cancer survivors performing exercise (e.g., 2–3 h of brisk walking/week) have a 40–67% reduction in breast cancer recurrence and all-cause mortality compared with inactive survivors [53],[54],[55]. Similar data were reported for prostate cancer where an average risk reduction ranged from 10%–30% [56],[57]. Recently, the evaluation of physical activity in relationship to prostate cancer mortality among 2,750 men diagnosed with prostate cancer showed that a modest amount of vigorous activity, such as biking, tennis, jogging, or swimming for 3 hours a week, may substantially improve prostate cancer-specific survival [58],[59].

However, the potential biologic mechanisms through which physical activity may decrease the risk of breast and prostate cancer are still elusive. Several putative etiologic pathways, including those involving steroid hormones, chronic inflammation, growth factors, lymphokines and insulin resistance were suggested (reviewed in Ref. [49]). On the other hand, there are mounting evidences that VIP pathway plays an important role in pathogenesis of breast and prostate cancer, indicating that elevated concentration of VIP, a facilitator of breast and prostate cancer, in the circulation may contribute to these diseases and that suppression of this peptide could have positive effect [24],[25],[26],[27],[28],[29].

The level of circulating VIP is controlled by natural anti-VIP antibodies [39],[40],[41],[42],[43] and we hypothesized that these suppressive antibodies could contribute to a better control of breast and prostate cancer and that lack of these antibodies could contribute to the progression of these diseases. In order to test this assumption we compared reactivity with peptide NTM1 of sera collected from cancer patients and healthy control. Results given in Table 1 and Figure 1 show that this reactivity is significantly lower in cancer patients in comparison with healthy control subjects.

Paul and Said showed that natural anti-VIP antibodies were present in plasma from 29.6% of healthy human subjects who habitually performed aerobic muscular exercise (running, cycling, swimming, aerobic dancing, and/or weight training, 3 or more workouts per week for a year or more prior to study entry), compared to 2.3% of healthy subjects who did not [37]. Herein, presented results show that a significantly higher percentage of trained athletes had increased titers of NTM1 reactive antibodies, 23 out of 28 (82.1%) females and 23 out of 26 (88.5%) males compared to non-athletes. This finding expanded our recent report on male water polo elite athletes [38] and strongly supported the suggestion that physical exercise represents a stimulus of the immune system which boosts production of natural VIP/NTM1-reactive antibodies.

The total IgG content in all cancer patients (11±2.7 mg/ml) and in elite athletes (11.2±2.9 mg/ml) was in the normal range (7–16 mg/ml) and comparable with normal values suggesting that that difference in the different age distribution of the athletic subjects (18–26) and cancer patients (56±3.9) did not significantly affect global function of the immune system, allowing comparison of immunological data obtained for these two studied groups. Thus, the reduced levels of natural antibodies recognizing peptide NTM1 in breast and prostate patients was specific and may contribute to disease progression.

The antigenic stimulus for the formation of natural VIP/NTM1-reactive antibodies could not be identified from our studies; however, several studies have demonstrated that acute exercise is associated with increased plasma levels of VIP [30],[31],[32],[33],[34],[35],[36]. It is thus plausible to theorize that these antibodies may have been produced in response to an increase in VIP levels during exercise, providing increased antigenic stimulus. In line with this hypothesis is that physical activity provides a potential source of the natural anti-VIP/NTM antibodies that could contribute to the control of breast and prostate cancer.

In order to keep the conclusions derived from this study under its real extent, it is necessary take into account that elite athletes are different from sedentary and even from physically active subjects, not just because of the exercise routine, but mainly for genetic predisposition allowing remarkable physiological and biological indexes. For this reason, we can't exclude the possibility that these specific genetic makeup of elite athletes could also partially contribute to their increased production of natural VIP/NTM1-reactive antibodies.

Herein we suggest a possible role for naturally produced antibodies reacting with peptides VIP and NTM1 in the control of breast and prostate cancer, which we believe could offer a possible molecular mechanism underlying positive effects of physical exercise in these cancers. Presented results strongly suggest further research of physical exercise as an important natural approach against breast and prostate cancer. Because little is known about the optimal level of exercise in combating of these cancers, variations in the mode, intensity, duration, and frequency of exercise prescriptions also requires future research.

Materials and Methods

Ethics statement

Informed consent and local ethics committee approval was obtained for these human studies. All patients provided written informed consent. The Ethical Committee for Clinical Trials of the Faculty of Pharmacy in Belgrade is responsible for the ethical conduct of this study.

Human subjects

Cancer patients.

Sera samples were collected from 15 subjects with breast and 17 subjects with prostate cancer (disease stage, values of tumor markers and the age are given in Table 2). Sera were collected immediately after confirmed diagnosis and before the start of any therapeutic intervention.

Athletic subjects.

Sera samples were collected from 54 Serbian elite international athletes (26 males and 28 females) engaged in the following types of sports activities: wrestling, water polo, rowing, karate, kick boxing, swimming and volleyball. Female and male elite athletes were engaged in the sport training in average 9 and 11 years, respectively. All athletes were tested at the end of basic preparatory mezocycle (a phase of training with duration of between 4–6 weeks) in a period of recuperative microcycle (shorter training period of about 7–10 days for active recuperation of the athletes) [60]. We expected that in this latter period, production of natural antibodies which clear VIP from circulation should have reached higher levels.


Sera samples were collected from 34 healthy (HIV-negative) individuals (17 males and 17 females) doing sedentary computer work 6–8 h a day and who were not performing regular physical exercise (healthy, sedentary subjects). The ages of all controls (18–26) matched the athletic subjects and there were no risk factors that would affect the immune system (cigarette smoke, alcohol consumption, use of medications, chronic diseases, etc).

Peptide conjugates synthesis

The synthesis of the (NTM1s)4-SOC4 conjugate was carried out manually by stepwise solid phase peptide synthesis using the Boc-Gly-OCH2-Pam resin (1 g, 0.25 mmol/g capacity). Sequential oligopeptide carrier (SOC4), formed by the repetitive Lys-Aib-Gly, is applied to display analyzed peptides. The synthetic procedure starts with the step-by-step couplings of the protected residues (Boc/Bzl) corresponding to the SOC4 carrier to the resin. Lysine was introduced as Boc-Lys(Fmoc)-OH. After removal of the Fmoc protective groups from the Lys-NεH2 groups by 20% piperidine in dimethylformamide, synthesis of the epitope FTDNAKTI was carried out (Boc/Bzl) by the simultaneous attachment of each residue in four copies.


ELISA was performed with peptide (NTM1s)4-SOC4 by the following procedure: polystyrene microtest plates (Sarstedt, Germany) were incubated overnight at 4°C with 100 µl of peptides (0.5 µg/well) diluted in carbonate buffer, pH 9.6. Plates were washed with phosphate-buffered saline (PBS)–0.05% Tween and non-specific sites were blocked with 200 μl PBS containing 5% bovine serum albumin (BSA) for 2 h at room temperature. After six washings, serum specimens were added to the wells (100 µl/well). Sera were diluted 1∶100 in 5% BSA in PBS. Plates were incubated for 3 h at room temperature. After six washings with PBS–0.05% Tween, 100 µl of goat anti-human IgG alkaline phoshatase-conjugated antibodies (Sigma), diluted 1∶2500 were added and the plates were incubated for 30 minutes at room temperature. After six washings, pNPP (p-Nitrophenyl Phosphate) substrate was added and the absorbance (OD) measured at 492–620 nm after 15 minutes. Each sample was tested independently twice and the mean values are reported.

Statistical analysis

The significance of the differences in O.D. values for individuals with breast and prostate cancer, elite athletes and control subjects was calculated by the non-parametrical Kruskal-Wallis. The two groups are unpaired with uneven variance and therefore they were considered as part of a two-tailed, heteroscedastic matrix. For each comparison, the level of significance p for a directional test is given.

Author Contributions

Conceived and designed the experiments: AC DB VV. Performed the experiments: MV NV. Analyzed the data: AC DB VV SG. Contributed reagents/materials/analysis tools: VD MD MSD. Wrote the paper: AC DB VV.


  1. 1. Gespach C, Bawab W, Chastre E, Emami S, Yanaihara N, et al. (1988) Pharmacology and molecular identification of vasoactive intestinal peptide (VIP) receptors in normal and cancerous gastric mucosa in man. Biochemical and biophysical research communications 151: 939–947.
  2. 2. Moody TW, Leyton J, Gozes I, Lang L, Eckelman WC (1998) VIP and breast cancer. Annals of the New York Academy of Sciences 865: 290–296.
  3. 3. Madsen B, Georg B, Madsen MW, Fahrenkrug J (2000) Downregulation of VPAC1R expression in breast cancer cell lines. Annals of the New York Academy of Sciences 921: 33–36.
  4. 4. Gespach C, Bawab W, de Cremoux P, Calvo F (1988) Pharmacology, molecular identification and functional characteristics of vasoactive intestinal peptide receptors in human breast cancer cells. Cancer research 48: 5079–5083.
  5. 5. Dagar S, Sekosan M, Rubinstein I, Onyuksel H (2001) Detection of VIP receptors in MNU-induced breast cancer in rats: implications for breast cancer targeting. Breast cancer research and treatment 65: 49–54.
  6. 6. Garcia-Fernandez MO, Collado B, Bodega G, Cortes J, Ruiz-Villaespesa A, et al. (2005) Pituitary adenylate cyclase-activating peptide/vasoactive intestinal peptide receptors in human normal mammary gland and breast cancer tissue. Gynecological endocrinology: the official journal of the International Society of Gynecological Endocrinology 20: 327–333.
  7. 7. Moody TW, Jensen RT (2006) Breast cancer VPAC1 receptors. Annals of the New York Academy of Sciences 1070: 436–439.
  8. 8. Moody TW, Gozes I (2007) Vasoactive intestinal peptide receptors: a molecular target in breast and lung cancer. Current pharmaceutical design 13: 1099–1104.
  9. 9. Moody TW, Hill JM, Jensen RT (2003) VIP as a trophic factor in the CNS and cancer cells. Peptides 24: 163–177.
  10. 10. Valdehita A, Carmena MJ, Collado B, Prieto JC, Bajo AM (2007) Vasoactive intestinal peptide (VIP) increases vascular endothelial growth factor (VEGF) expression and secretion in human breast cancer cells. Regulatory peptides 144: 101–108.
  11. 11. Valdehita A, Bajo AM, Fernandez-Martinez AB, Arenas MI, Vacas E, et al. (2010) Nuclear localization of vasoactive intestinal peptide (VIP) receptors in human breast cancer. Peptides 31: 2035–2045.
  12. 12. Valdehita A, Bajo AM, Schally AV, Varga JL, Carmena MJ, et al. (2009) Vasoactive intestinal peptide (VIP) induces transactivation of EGFR and HER2 in human breast cancer cells. Molecular and cellular endocrinology 302: 41–48.
  13. 13. Valdehita A, Carmena MJ, Bajo AM, Prieto JC (2011) RNA interference-directed silencing of VPAC(1) receptor inhibits VIP effects on both EGFR and HER2 transactivation and VEGF secretion in human breast cancer cells. Molecular and cellular endocrinology.
  14. 14. Collado B, Gutierrez-Canas I, Rodriguez-Henche N, Prieto JC, Carmena MJ (2004) Vasoactive intestinal peptide increases vascular endothelial growth factor expression and neuroendocrine differentiation in human prostate cancer LNCaP cells. Regulatory peptides 119: 69–75.
  15. 15. Collado B, Sanchez-Chapado M, Prieto JC, Carmena MJ (2006) Hypoxia regulation of expression and angiogenic effects of vasoactive intestinal peptide (VIP) and VIP receptors in LNCaP prostate cancer cells. Molecular and cellular endocrinology 249: 116–122.
  16. 16. Collado B, Carmena MJ, Clemente C, Prieto JC, Bajo AM (2007) Vasoactive intestinal peptide enhances growth and angiogenesis of human experimental prostate cancer in a xenograft model. Peptides 28: 1896–1901.
  17. 17. Sotomayor S, Carmena MJ, Schally AV, Varga JL, Sanchez-Chapado M, et al. (2007) Transactivation of HER2 by vasoactive intestinal peptide in experimental prostate cancer: Antagonistic action of an analog of growth-hormone-releasing hormone. International journal of oncology 31: 1223–1230.
  18. 18. Gutierrez-Canas I, Juarranz MG, Collado B, Rodriguez-Henche N, Chiloeches A, et al. (2005) Vasoactive intestinal peptide induces neuroendocrine differentiation in the LNCaP prostate cancer cell line through PKA, ERK, and PI3K. The Prostate 63: 44–55.
  19. 19. Nagakawa O, Junicho A, Akashi T, Koizumi K, Matsuda T, et al. (2005) Vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide stimulate interleukin-6 production in prostate cancer cells and prostatic epithelial cells. Oncology reports 13: 1217–1221.
  20. 20. Gkonos PJ, Ashby MH, Andrade AA (1996) Vasoactive intestinal peptide stimulates prostate-specific antigen secretion by LNCaP prostate cancer cells. Regulatory peptides 65: 153–157.
  21. 21. Fernandez-Martinez AB, Bajo AM, Sanchez-Chapado M, Prieto JC, Carmena MJ (2009) Vasoactive intestinal peptide behaves as a pro-metastatic factor in human prostate cancer cells. The Prostate 69: 774–786.
  22. 22. Fernandez-Martinez AB, Bajo AM, Isabel Arenas M, Sanchez-Chapado M, Prieto JC, et al. (2010) Vasoactive intestinal peptide (VIP) induces malignant transformation of the human prostate epithelial cell line RWPE-1. Cancer letters 299: 11–21.
  23. 23. Rekasi Z, Schally AV, Plonowski A, Czompoly T, Csernus B, et al. (2001) Regulation of prostate-specific antigen (PSA) gene expression and release in LNCaP prostate cancer by antagonists of growth hormone-releasing hormone and vasoactive intestinal peptide. The Prostate 48: 188–199.
  24. 24. Zia H, Hida T, Jakowlew S, Birrer M, Gozes Y, et al. (1996) Breast cancer growth is inhibited by vasoactive intestinal peptide (VIP) hybrid, a synthetic VIP receptor antagonist. Cancer research 56: 3486–3489.
  25. 25. Moody TW, Leyton J, Chan D, Brenneman DC, Fridkin M, et al. (2001) VIP receptor antagonists and chemotherapeutic drugs inhibit the growth of breast cancer cells. Breast cancer research and treatment 68: 55–64.
  26. 26. Moody TW, Dudek J, Zakowicz H, Walters J, Jensen RT, et al. (2004) VIP receptor antagonists inhibit mammary carcinogenesis in C3(1)SV40T antigen mice. Life sciences 74: 1345–1357.
  27. 27. Moody TW, Czerwinski G, Tarasova NI, Michejda CJ (2002) VIP-ellipticine derivatives inhibit the growth of breast cancer cells. Life sciences 71: 1005–1014.
  28. 28. Moody TW, Mantey SA, Fuselier JA, Coy DH, Jensen RT (2007) Vasoactive intestinal peptide-camptothecin conjugates inhibit the proliferation of breast cancer cells. Peptides 28: 1883–1890.
  29. 29. Plonowski A, Varga JL, Schally AV, Krupa M, Groot K, et al. (2002) Inhibition of PC-3 human prostate cancers by analogs of growth hormone-releasing hormone (GH-RH) endowed with vasoactive intestinal peptide (VIP) antagonistic activity. International journal of cancer Journal international du cancer 98: 624–629.
  30. 30. Galbo H, Hilsted J, Fahrenkrug J, Schaffalitzky De Muckadell OB (1979) Fasting and prolonged exercise increase vasoactive intestinal polypeptide (VIP) in plasma. Acta physiologica Scandinavica 105: 374–377.
  31. 31. Oktedalen O, Opstad PK, Fahrenkrug J, Fonnum F (1983) Plasma concentration of vasoactive intestinal polypeptide during prolonged physical exercise, calorie supply deficiency, and sleep deprivation. Scandinavian journal of gastroenterology 18: 1057–1062.
  32. 32. Oektedalen O, Opstad PK, Schaffalitzky de Muckadell OB, Fausa O, Flaten O (1983) Basal hyperchlorhydria and its relation to the plasma concentrations of secretin, vasoactive intestinal polypeptide (VIP) and gastrin during prolonged strain. Regulatory peptides 5: 235–244.
  33. 33. Oktedalen O, Opstad PK, Schaffalitzky de Muckadell OB (1983) The plasma concentrations of secretin and vasoactive intestinal polypeptide (VIP) after long-term, strenuous exercise. European journal of applied physiology and occupational physiology 52: 5–8.
  34. 34. Woie L, Kaada B, Opstad PK (1986) Increase in plasma vasoactive intestinal polypeptide (VIP) in muscular exercise in humans. General pharmacology 17: 321–326.
  35. 35. Opstad PK (1987) The plasma vasoactive intestinal peptide (VIP) response to exercise is increased after prolonged strain, sleep and energy deficiency and extinguished by glucose infusion. Peptides 8: 175–178.
  36. 36. MacLaren DP, Raine NM, O'Connor AM, Buchanan KD (1995) Human gastrin and vasoactive intestinal polypeptide responses to endurance running in relation to training status and fluid ingested. Clinical science 89: 137–143.
  37. 37. Paul S, Said SI (1988) Human autoantibody to vasoactive intestinal peptide: increased incidence in muscular exercise. Life sciences 43: 1079–1084.
  38. 38. Veljkovic M, Dopsaj V, Stringer WW, Sakarellos-Daitsiotis M, Zevgiti S, et al. (2010) Aerobic exercise training as a potential source of natural antibodies protective against human immunodeficiency virus-1. Scandinavian journal of medicine & science in sports 20: 469–474.
  39. 39. Paul S, Heinz-Erian P, Said SI (1985) Autoantibody to vasoactive intestinal peptide in human circulation. Biochemical and biophysical research communications 130: 479–485.
  40. 40. Paul S, Volle DJ, Beach CM, Johnson DR, Powell MJ, et al. (1989) Catalytic hydrolysis of vasoactive intestinal peptide by human autoantibody. Science 244: 1158–1162.
  41. 41. Paul S, Volle DJ, Powell MJ, Massey RJ (1990) Site specificity of a catalytic vasoactive intestinal peptide antibody. An inhibitory vasoactive intestinal peptide subsequence distant from the scissile peptide bond. The Journal of biological chemistry 265: 11910–11913.
  42. 42. Mei S, Mody B, Eklund SH, Paul S (1991) Vasoactive intestinal peptide hydrolysis by antibody light chains. The Journal of biological chemistry 266: 15571–15574.
  43. 43. Paul S, Mei S, Mody B, Eklund SH, Beach CM, et al. (1991) Cleavage of vasoactive intestinal peptide at multiple sites by autoantibodies. The Journal of biological chemistry 266: 16128–16134.
  44. 44. Veljkovic V, Metlas R, Raspopovic J, Pongor S (1992) Spectral and sequence similarity between vasoactive intestinal peptide and the second conserved region of human immunodeficiency virus type 1 envelope glycoprotein (gp120): possible consequences on prevention and therapy of AIDS. Biochemical and biophysical research communications 189: 705–710.
  45. 45. Velikovic V, Metlas R, Danilo V, Cavor L, Pejinovic N, et al. (1993) Natural autoantibodies cross-react with a peptide derived from the second conserved region of HIV-1 envelope glycoprotein gp120. Biochemical and biophysical research communications 196: 1019–1024.
  46. 46. Veljkovic N, Branch DR, Metlas R, Prljic J, Vlahovicek K, et al. (2003) Design of peptide mimetics of HIV-1 gp120 for prevention and therapy of HIV disease. The journal of peptide research: official journal of the American Peptide Society 62: 158–166.
  47. 47. Veljkovic V, Veljkovic N, Metlas R (2004) Molecular makeup of HIV-1 envelope protein. International reviews of immunology 23: 383–411.
  48. 48. Djordjevic A, Veljkovic M, Antoni S, Sakarellos-Daitsiotis M, Krikorian D, et al. (2007) The presence of antibodies recognizing a peptide derived from the second conserved region of HIV-1 gp120 correlates with non-progressive HIV infection. Current HIV research 5: 443–448.
  49. 49. Friedenreich CM (2010) Physical Activity and Breast Cancer: Review of the Epidemiologic Evidence and Biologic Mechanisms. 188: 125–139.
  50. 50. Frisch RE, Wyshak G, Witschi J, Albright NL, Albright TE, et al. (1987) Lower lifetime occurrence of breast cancer and cancers of the reproductive system among former college athletes. International journal of fertility 32: 217–225.
  51. 51. Frisch RE, Wyshak G, Albright NL, Albright TE, Schiff I, et al. (1992) Former athletes have a lower lifetime occurrence of breast cancer and cancers of the reproductive system. Advances in experimental medicine and biology 322: 29–39.
  52. 52. Wyshak G, Frisch RE (2000) Breast cancer among former college athletes compared to non-athletes: a 15-year follow-up. British journal of cancer 82: 726–730.
  53. 53. Irwin ML, Smith AW, McTiernan A, Ballard-Barbash R, Cronin K, et al. (2008) Influence of pre- and postdiagnosis physical activity on mortality in breast cancer survivors: the health, eating, activity, and lifestyle study. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 26: 3958–3964.
  54. 54. McTiernan A, Irwin M, Vongruenigen V (2010) Weight, physical activity, diet, and prognosis in breast and gynecologic cancers. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 28: 4074–4080.
  55. 55. Ibrahim EM, Al-Homaidh A (2010) Physical activity and survival after breast cancer diagnosis: meta-analysis of published studies. Medical oncology.
  56. 56. Torti DC, Matheson GO (2004) Exercise and prostate cancer. Sports medicine 34: 363–369.
  57. 57. Leitzmann MF (2011) Physical activity and genitourinary cancer prevention. Recent results in cancer research Fortschritte der Krebsforschung Progres dans les recherches sur le cancer 186: 43–71.
  58. 58. Kenfield SA, Stampfer MJ, Giovannucci E, Chan JM (2011) Physical activity and survival after prostate cancer diagnosis in the health professionals follow-up study. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 29: 726–732.
  59. 59. Richman EL, Kenfield SA, Stampfer MJ, Paciorek A, Carroll PR, et al. (2011) Physical Activity after Diagnosis and Risk of Prostate Cancer Progression: Data from the Cancer of the Prostate Strategic Urologic Research Endeavor. Cancer research.
  60. 60. Bompa TO, Carrera M (2005) Periodization training for sports. Champaign, IL: Human Kinetics. ix, 259: